What to Order When FAQs

It depends on the hardware. Ferromagnetic materials such as Iron, Cobalt, and Nickel are not typically MRI compatible. Non-ferromagnetic materials such as Aluminium, Titanium, and Copper are typically MRI compatible. Every patient will receive an MRI Screening Form from their MRI technologist prior to entering the magnetic field. The MRI Screening Form will ask about prior surgeries, implantable hardware, shrapnel, and pregnancy status to ensure patient safety. Many patients carry a card that identifies the relevant information about their implanted hardware/device with regards to MRI compatibility. Most institutions and technologists use the website here to check for MRI compatibility using the information from the patient’s card.

Typically Yes as long as the shrapnel is not located around the eyes or near a major nerve or blood vessel. The primary concern involving metallic foreign bodies is heating and micromotion of the metal and subsequent damage to the surrounding tissues. For the vast majority of patients, the tiny metallic fragments do not pose a significant threat. All MRI patients have the ability to activate a call button while inside the scanner if they experience any unusual sensations. The MRI technologist will then stop the exam and remove the patient from the magnetic field.

Typically No. Most Implantable Cardiac Devices (ICDs) are not MRI compatible. A few ICDs are specifically designed to be MRI compatible. Some institutions have an “MRI Pacemaker Protocol” where a device representative or Cardiologist deactivates the ICD before the MRI scan, the patient is continuously monitored with cardiac telemetry during the MRI, and then the device representative or Cardiologist reactivates the ICD and ensures proper functioning before the cardiac telemetry is discontinued. This is typically only performed at large academic centers and not available at most hospitals.

If a stent has been placed in the United States within the last 10 – 15 years, it is almost certainly MRI compatible. Aneurysm coils and/or clips may or may not be MRI compatible. Some pacemakers/ICDs are MRI compatible, but most are not. Any implantable device or hardware that is not clearly MRI compatible will be screened by the MRI technologist prior to performing the exam and many patients carry a card that identifies the relevant information about their implanted hardware with regards to MRI compatibility. Most institutions and technologists use the website here to check for MRI compatibility. Only in emergent situations, with physician authorization, can a patient be scanned prior to checking MRI compatibility of an implantable device.

IV CT Contrast is rapidly filtered through the kidneys and excreted into the urine. Depending on when the CT is acquired, relative to the time of IV injection, the contrast will be inside different vascular or urinary compartments and thus, the CT will look different. Excluding the Non-contrast phase, there are roughly 5 different phases of enhancement (Early Arterial or “Angiographic”, Late Arterial or “Arterial”, Late Portal or “Portal Venous”, Nephrographic, and Delayed or “Excretory”). These phases progress in a very predictable order and radiologists use the different phases of contrast enhancement to optimize the CT for a particular diagnosis/organ of interest. Angiographic Phase imaging is typically acquired using a bolus tracking technique to ensure that all of the contrast is in the arteries and has not yet enhanced the organs or other soft tissues. This phase is useful to evaluate patency, stenosis or dissection of a specific artery – think of the Pulmonary Artery in a CTA Chest (PE Protocol) or the Vertebral Artery in a CTA Neck. Arterial Phase imaging is typically acquired ~30s after injection and is used to characterize arterially hyperenhancing/hypervascular tumors – think of HCC in the liver. Portal Venous Phase imaging is typically acquired ~70s after injection and is the most common phase of CT imaging in the abdomen and pelvis. It is used for everything from appendicitis, to pain, to infection, to malignancy, to trauma. Nephrographic Phase imaging is typically acquired ~90s after injection and is when the kidneys are most homogeneously bright/enhancing. Delayed Phase imaging can be acquired anywhere between ~5 – 15 minutes after injection. At this point in time, the contrast has been filtered through the kidneys and is now opacifying the ureters and bladder. When the Delayed Phase is acquired as part of a CT protocol, it is sometimes referred to as a CT Urogram. It is important to note that each “Phase” of imaging requires a separate pass through the CT scanner and therefore a separate dose of radiation to the target area. For example, a 4 Phase Liver CT requires 4 passes through the CT scanner and 4 doses of radiation to the abdomen. It will typically include Non-contrast, Arterial, Portal Venous, and Delayed Phases of imaging (4 Phases = 4 Passes = 4 times the radiation dose).

Well, you could order a CT or MRI of an entire limb, but it may not answer your clinical question. If there is concern for internal derangement of a joint (small non-displaced fracture, cartilage injury, torn ligament, or torn tendon), then those specific joints should be imaged separately. A long bone field of view (i.e. MRI Humerus) cannot adequately evaluate the many, small internal structures of joints (shoulder or elbow in this example) due to decreased spatial resolution. Increasing the field of view decreases the spatial resolution of the images. This means that scanning large areas creates a “fuzzy” image, whereas focused small field of view scanning creates “sharp/detailed” images. The internal structures of most joints are typically too small to reliably be evaluated by large field of view/low spatial resolution imaging. However, if the clinical question is to evaluate for something besides a small, non-displaced fracture or ligament tear (i.e. generalized pain, tumor, edema, osteomyelitis, cellulitis), then a large field of view MRI may be adequate. This concept can be applied to all areas of MRI and CT imaging and is why CT Temporal Bone or MRI Internal Auditory Canal (IAC) exams exist – small structures, like the ones in the inner ear, require small field of view/high resolution imaging and are unable to be resolved by the larger field of view MRI Brain or CT Head.

The weight limit depends on the model of CT scanner although 450-500 lbs is the range of maximum weight limits for most CT scanners. Also, most CT bores cannot accommodate patients larger than 70 cm in diameter. Some bariatric scanners can image patients up to 650 lbs and have large bores up to 90 cm in diameter.

The weight limit depends on the model of MRI scanner although 350-400 lbs is the range of maximum weight limits for most MRI scanners. Also, most MRI bores cannot accommodate patients larger than 60-70 cm in diameter. Open MRI scanners can image larger patients up to 650 lbs and do not have a typical round bore that limits patient diameter.

An MRI can take between 30-60 min to complete and requires the patient to lay still throughout the entire exam. MRI image motion degradation can be from claustrophobia, anxiety and/or discomfort/pain. Patients who cannot tolerate lying still for a long period of time are often rescheduled with mild sedation.

There is no specific premedication regimen for MRI anxiolysis. Oral Benzodiazepines are frequently used for mild MRI sedation. Many people choose Ativan/Lorazepam or Valium/Diazepam and the dose required is very patient-dependent. IV Conscious Sedation is a more powerful method of anxiolysis and typically involves the administration of Versed/Midazolam and Fentanyl.

For MRI or CT imaging of palpable masses, it is best to order a single exam that best fits the field of view (i.e. MRI Shoulder for an axillary mass) then clearly specify in the indication “Do not perform routine field of view. Please mark the superior and inferior borders of the palpable mass with skin surface markers, center the field of view over this mass, and tailor the exam to include complete coverage of this lesion.” That wording should ensure that the technologist recognizes the nuance of the exam and that he or she will call their radiologist with any further questions. It also increases the possibility that the patient/system will only be charged for a single MRI instead of 2 exams (i.e. MRI Shoulder + MRI Humerus for an axillary mass).

The “T” stands for Tesla which is a measure of magnetic field strength. MRIs can range from 0.3T to 7T, but most magnets/MRI machines in practice today are either 1.5T or 3T. Magnets below 1T suffer from poor signal to noise ratio creating grainy/low resolution images. Magnets above 3T are essentially nonclinical and predominantly used for research purposes. 7T magnets are typically located at academic centers. In general, a 3T magnet will produce better quality images than a 1.5T magnet, however that is assuming that both magnets are equally optimized and have excellent Surface Radiofrequency Coils to receive the signal. MRI machine optimization is probably the most important factor in generating quality images, not necessarily the magnetic field strength. An optimized 1.5T magnet with excellent surface coils and software upgrades can produce better images than a nonoptimized 3T magnet. Furthermore, better technical quality (higher signal to noise ratio from 3T vs 1.5T) does not necessarily mean increased diagnostic accuracy. Most pathology seen on 3T can also be identified on 1.5T. Therefore, assuming quality MRI technicians and ancillary equipment, 1.5T MRI images are diagnostically equivalent to 3T MRI images even if they are slightly lower in resolution. There are a few exceptions to the “1.5T is roughly equivalent to 3T” rule however, the major one being imaging of the labrum. 3T imaging of the labrum is clearly superior to 1.5T imaging. If available, all MRI Arthrograms should be done with 3T imaging. 3T is also slightly superior to 1.5T in imaging small joints of the fingers and toes. Again, this is assuming that the surface coils are of high quality. A 1.5T magnet with a dedicated small extremity coil may produce better images than a 3T magnet with a larger surface coil. 3T can acquire images at a faster speed than 1.5T magnets. This may produce better overall images as patients move around more (create more motion artifact) the longer the scan time. All total joint arthroplasties should be performed on a 1.5T magnet as metallic hardware artifact increases with increasing magnetic field strength.

Yes. Approximately 1 – 2% of oral contrast is absorbed through the GI tract therefore there is a theoretical risk for a contrast reaction. If the patient has had a history or a mild or moderate allergic reaction to IV CT Contrast, then routine Oral Contrast can be administered. If the patient has a history of anaphylaxis from IV CT Contrast, then an oral barium solution can be used instead of the routine iodinated oral contrast.

It’s hard to say without knowing the exact question and clinical scenario but there are some general guidelines you can follow to help you decide between a CT and an MRI. For imaging of the lungs, CT is the best exam. For imaging of chest wall trauma (scapula, ribs, sternum, etc.), CT is the best exam. For imaging of acute trauma, CT and CTA are usually the best exams. Cases where MRI is probably the better exam include spinal cord trauma and musculoskeletal trauma without an acute fracture seen on x-ray. For imaging of possible acute traumatic fractures seen on x-ray, CT is usually the best exam. While MRI is more sensitive for fractures because it can easily pick up bone marrow edema around tiny, non-displaced and easily missed fractures, it often does not have the resolution to identify tiny fracture fragments and bony avulsions. The fragments are essentially engulfed by the bone marrow/soft tissue edema and are sometimes strikingly obvious on x-ray but essentially invisible on MRI. Cases where MRI is probably the better exam include imaging of stress fractures/stress reactions (around the knee, tibia, and foot), sacral insufficiency fractures, or involve the dating of compression fractures of the spine. For imaging of cartilage, tendons, ligaments, labrum, and muscles, MRI is the best exam. CT can detect intramuscular hematomas, but is much less sensitive than MRI. If the hematoma is less than ~ 3cm, it may be difficult to visualize with CT. CT cannot detect muscle strains and contusions. CT cannot reliably detect tendon and ligament injuries. CT cannot detect cartilage injuries. CT and MRI are probably equally sensitive in detecting subcutaneous edema. For brain imaging, CT is the best exam for acute trauma where there is concern for a skull fracture or intracranial hemorrhage. For parenchymal abnormalities such as tumors, demyelinating lesions, and infarcts, MRI is the best exam. However, CT can detect tumors and infarcts with reasonable sensitivity and is therefore the recommended initial exam for ER patients, acutely symptomatic patients, and as a screening exam for low-risk patients who present with vague symptoms such as altered mental status.

Most MRI machines are Closed meaning that there is a big metal circle that the MRI table slides into. Open MRIs have multiple different designs but in essence, they are not an enclosed circle and have an opening in the top or on the sides. Closed MRI machines are always superior to Open MRIs. Open MRIs are designed for claustrophobic or very large patients (~400+ lbs) who cannot tolerate/fit into the closed bore (metal circle) of the MRI. Open MRIs cannot generate as strong of a magnetic field as a Closed MRI and therefore produce much lesser quality images. Realistically, only large/obvious pathology in large joints (shoulders and knees) is visible on an open MRI. Spine imaging is limited and often only large disc herniations are visible. Imaging of the wrists, hands, feet, etc. are severely limited with an open MRI. If the patient can tolerate a Closed MRI, he or she should receive one. Even if the patient is claustrophobic or very large, he or she should try to fit into the closed MRI first before being scheduled in an Open MRI. There are narrow-bore and wide-bore versions of the Closed MRI machines so it may be worth checking to see if there is a wide-bore Closed MRI available prior to sending the patient for an Open MRI. Note that many claustrophobic patients will be able to tolerate a Closed MRI with appropriate premedication, especially if the lower half of the body is being scanned. For example, the patients chest, head and neck will be out of the magnet bore for an MRI of the ankle.

No. The standard CT Trauma Body Protocol (CT Chest, Abdomen, and Pelvis With IV Contrast) is sufficient to exclude GI trauma in almost all cases. Some institutions administer rectal contrast as part of their routine trauma CT protocol for high velocity trauma patients, however this is unnecessary as it delays care, increases cost, and is uncomfortable for patients. If there are truly equivocal findings on the initial CT with just IV Contrast, then Rectal Contrast or Oral Contrast can be administered and the patient can be re-scanned.

Rectal contrast is ideal for staging Colorectal Cancer on MRI. It is not absolutely necessary however and most cases will be adequately staged without the administration of rectal contrast, particularly if there has been a good pre-imaging colon prep (similar to colonoscopy). Rectal contrast is not routinely administered for cancer staging at some institutions. The utility of rectal contrast is to distend the bowel and help characterize the depth of colorectal wall invasion by the cancer.

The exact pathophysiology of Contrast Induced Nephropathy (CIN) is not well understood and there are no great published studies on this entity. “At the current time, there is very little evidence that IV [CT] Contrast material is an independent risk factor for Acute Kidney Injury (AKI) in patients with eGFR >/= 30 mL / min/1.73m2. Therefore, if a threshold for CIN risk is used at all, 30 mL/min/1.73m2 seems to be the one with the greatest level of evidence. Any threshold put into practice must be weighed on an individual patient level with the benefits of administering contrast material.” The above information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information. As a rule of thumb, however, if the patient is not in AKI and the eGFR is > 60 mL/min, then IV CT Contrast can be safely administered. If the patient has an eGFR of between 30-59 mL/min, then IV CT Contrast is usually safe as long as the patient is given IV hydration and does not have multiple other risk factors for CIN such as poor renal perfusion, currently taking nephrotoxic drugs, currently in AKI, or diabetes. And if the patient has an eGFR of < 30mL/min, then IV CT Contrast is typically not administered unless there is physician approval in cases of medical necessity. If the patient is critically ill and has multiple comorbidities (i.e. an ICU patient with Diabetes, CKD and CHF on “pressors”/inotropic support), click here for a CIN Risk Calculator. Please note that the data collected for the study which the calculator is based on comes from a cohort of very ill patients, many of whom had baseline CKD Stage 3 or 4, and may have been in AKI or taking nephrotoxic drugs that the study does not account for. Therefore, this likely overestimates the risk for CIN, particularly if the calculator is used to determine risk in the general population/ER setting.

It depends on the type of MRI Contrast. Group 1 and Group 3 gadolinium agents are contraindicated in patients with Acute Kidney Injury (AKI) or Severe Chronic Renal Disease (GFR < 30 mL/min/1.73 m2) due to the risk of Nephrogenic Systemic Sclerosis (NSF). Group 2 gadolinium agents (MultiHance, Gadovist, Dotarem, Clariscan, and ProHance) have little to no risk of NSF according to recent data. Specifically, a recent systematic review and meta-analysis evaluated the pooled risks of NSF in patients with stage 4 or 5 chronic kidney disease receiving a Group 2 gadolinium-based contrast agent. The authors analyzed 16 studies with 4,931 patients who received Group 2 agents. The pooled risk of NSF was 0% (upper bound of 95% CI 0.07%). Thus, they estimated the per-patient risk of NSF from receiving Group 2 gadolinium-based contrast agents in stage 4 or 5 chronic kidney disease to be less than 0.07%. The American College of Radiology (ACR) permits the use of Group 2 gadolinium agents in patients with advanced kidney disease if the exam is medically necessary and recommends using the lowest dose possible to achieve diagnostic quality imaging. NSF is very rare, even in patients with poor renal function, but it is an irreversible complication of IV MRI Contrast administration where Gadolinium precipitates out of the bloodstream and into the tissues causing multiorgan, multi-system fibrosis. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

The short answer is that CT works well when looking at bone injuries, while MRI can provide more detailed information about the soft tissues of the body. The more complete answer is that it’s hard to say without knowing the exact question and clinical scenario, but there are some general guidelines you can follow to help you decide between a CT and an MRI. For imaging of the lungs, CT is the best exam. For imaging of chest wall trauma (scapula, ribs, sternum, etc.), CT is the best exam. For imaging of acute trauma, CT and CTA are usually the best exams. Cases where MRI is probably the better exam include spinal cord trauma and musculoskeletal trauma without an acute fracture seen on x-ray. For imaging of possible acute traumatic fractures seen on x-ray, CT is usually the best exam. While MRI is more sensitive for fractures because it can easily pick up bone marrow edema around tiny, non-displaced and easily missed fractures, it often does not have the resolution to identify tiny fracture fragments and bony avulsions. The fragments are essentially engulfed by the bone marrow/soft tissue edema and are sometimes strikingly obvious on x-ray but essentially invisible on MRI. Cases where MRI is probably the better exam include imaging of stress fractures/stress reactions (around the knee, tibia, and foot), sacral insufficiency fractures, or involve the dating of compression fractures of the spine. For imaging of cartilage, tendons, ligaments, labrum, and muscles, MRI is the best exam. CT can detect intramuscular hematomas, but is much less sensitive than MRI. If the hematoma is less than ~ 3cm, it may be difficult to visualize with CT. CT cannot detect muscle strains and contusions. CT cannot reliably detect tendon and ligament injuries. CT cannot detect cartilage injuries. CT and MRI are probably equally sensitive in detecting subcutaneous edema. For brain imaging, CT is the best exam for acute trauma where there is concern for a skull fracture or intracranial hemorrhage. For parenchymal abnormalities such as tumors, demyelinating lesions, and infarcts, MRI is the best exam. However, CT can detect tumors and infarcts with reasonable sensitivity and is therefore the recommended initial exam for ER patients, acutely symptomatic patients, and as a screening exam for low-risk patients who present with vague symptoms such as altered mental status.

A CT Urogram is a CT protocol that is typically done to evaluate hematuria, suspected renal or urothelial neoplasm, ureteral trauma, or congenital abnormalities of the kidneys and ureters. It consists of 3 phases: a Noncontrast Phase to look for renal stones, a Nephrographic Phase to evaluate the renal parenchyma and vasculature, and a Delayed Phase to evaluate for any filling defects or extravasation of the ureters and bladder. Commonly the last two phases are combined using a split-bolus technique where the contrast bolus is literally split and administered at ~7-15 min prior to scanning and at ~90s prior to scanning. This allows us to evaluate the renal parenchyma, vasculature and excretory system (ureters and bladder) with just one acquisition, resulting in a decreased radiation dose. In short, a CT Urogram evaluates the kidneys, ureters, and bladder using a Noncontrast CT and a Dual Phase Nephrographic and Delayed CT (split-bolus technique).

In general, if the indication is to evaluate for Trauma, Tumor/Mass, Infection, or a Vascular Abnormality, then IV Contrast is recommended. Common indications for CT Chest Without Contrast are: Rib Fracture, Pleural Effusion evaluation, Pneumothorax/Pneumomediastinum, Pulmonary Nodule Follow up, and Chronic Dyspnea/Interstitial Lung Disease.

IV Contrast is almost always recommended for CT Abdomen and Pelvis as long as there is no contraindication such as Allergy or Renal Insufficiency. Common indications for CT Abdomen and Pelvis Without Contrast are: Renal Stone and Retroperitoneal Hemorrhage.

Oral contrast, while helpful sometimes, is not necessary in most patients. It is not typically recommended in the ER setting because it can delay care. As a general rule of thumb, if the patient has a BMI of > 25, Oral Contrast does not increase the diagnostic accuracy of the exam. Oral Contrast is most helpful in stressing bowel anastomoses to assess for anastomotic leak or if the patient is very thin and the internal organs/bowel loops are difficult to separate with just IV Contrast. Or, if IV contrast cannot be administered, oral contrast can be helpful. Consult a radiologist if the patient has complex internal anatomy and you believe that oral contrast would be helpful. Cases to consider for oral contrast administration are as follows: Pediatric Appendicitis. Prior bowel surgery and concern for Native Bowel or Anastomotic Leak/Perforation. Concern for Bowel Fistula. Gastric Bypass. Esophageal Tear. Determining Partial vs Complete Small Bowel Obstruction with serial abdominal X-Rays and/or CTs. G-Tube or drain integrity (contrast injected through tube to assess for leak).

A Noncontrast Chest CT is adequate for most chest pathology including pulmonary nodules, masses, edema, and pneumonia. Noncontrast Chest CTs can diagnose pleural effusions but cannot diagnose an empyema unless there is gas in the pleural space, which is a rare finding. Noncontrast Chest CTs are adequate most of the time to evaluate for mediastinal and hilar adenopathy, but a contrast-enhanced exam is far superior as it clearly delineates vessels from nodes and other masses which can be missed on noncontrast exams, particularly in the hilum. Contrast is required to evaluate any vascular pathology in the chest such as Pulmonary Embolism or Aortic Dissection. Contrast is also needed to diagnose Pericarditis. Contrast-enhanced CTs are better at evaluating pneumonia because it can show early necrotizing pneumonia as demonstrated by hypo or non-enhancing pulmonary parenchyma. As a general rule of thumb, any vascular or mediastinal pathology is better evaluated by a CT Chest With Contrast whereas most lung pathology will be adequately evaluated despite the lack of IV CT Contrast.

In general, with the exception of renal stones, IV CT Contrast is ALWAYS preferred and greatly increases diagnostic accuracy. Renal stones, while less conspicuous on post-contrast exams, do not present diagnostic dilemmas and if multiple intra-abdominal pathologies are being considered, one of them being nephrolithiasis, it is better to give IV contrast and provide the radiologist with appropriate history regarding stones as a differential consideration than to perform a noncontrast exam or a CT With and Without Contrast. If IV contrast cannot be administered, then the quality of the exam becomes dependent on how much “intrinsic” contrast the patient has i.e. visceral fat. As a general rule of thumb, if the patient has a BMI > 25, then they will typically have enough visceral fat between organs to allow for accurate diagnosis of pathology. If there is a paucity of visceral fat (pediatric patients), then it becomes much more difficult to diagnose intra-abdominal pathology. This is why most pediatric CTs of the Abdomen and Pelvis include Oral Contrast – to increase the intrinsic contrast/help differentiate bowel from other organs or bowel from a pathological process, such as an abscess (an abscess < 3 cm can easily be mistaken for bowel and missed on a non-contrast exam). Oral Contrast is recommended in patients who cannot receive IV CT Contrast and/or have a BMI < 25. Noncontrast CTs are inadequate in evaluating trauma patients because they can miss solid organ lacerations. Noncontrast Trauma CTs are appropriate if the only concern is for fracture.

Yes. Renal stones, while less conspicuous on post-contrast exams, do not present diagnostic dilemmas and if multiple intra-abdominal pathologies are being considered, one of them being nephrolithiasis, it is better to give IV contrast and provide the radiologist with appropriate history regarding stones as a differential consideration than to perform a noncontrast exam or a CT With and Without Contrast.

Start with a frontal (Upright or Supine) Abdominal X-ray, 2 images. The first one is a baseline exam and the second image is taken after injection of ~30-50 mL of dilute contrast (50% tap water and 50% water-soluble contrast such as Gastrografin). If there is no extra-luminal contrast (Gastrografin leaking outside of the stomach) on this X-ray, then the G-tube is considered appropriately positioned and typically no further imaging is required. If there is persistent concern or if a more definitive answer is required, inject the Gastrografin through the G-tube, wait 15 min, and then perform a CT Abdomen and Pelvis With IV Contrast. Do not give oral contrast.

The tip of the NG/OG tube should ideally be located >/= 10 cm distal to the GE junction. This is because the side port of the NG/OG tube is ~ 10 cm proximal to the end of the tube and puts the patient at higher risk for aspiration if the NG/OG tube is used to deliver medication or other substances.

The tip of the ETT should ideally be located 5 cm +/- 2 cm proximal to the carina. If the ETT is too high, the inflated cuff can injure the vocal cords. If the ETT is too low, it puts the patient at risk for mainstem bronchus intubation and resultant contralateral whole lung atelectasis.

The tip of the CVL/CVC (PICC line, IJ line, Subclavian line, Port) should ideally be located at the atriocaval junction, where the SVC meets the right atrium. Positioning within the SVC or proximal right atrium is also acceptable. If the CVL/CVC is too high, there is theoretical suboptimal infusion of medication into the systemic circulation and a higher chance that the line will migrate out of the SVC and into the azygos, subclavian, or IJ veins. If the CVL/CVC is too low, there is increased risk for cardiac arrhythmia.

Ideally, the tip of the Swan is located in the mid right pulmonary artery, but there are multiple appropriate locations of the Swan-Ganz Catheter. As long as the tip is not too proximal (intracardiac) or too distal (in the pulmonary artery lobar or segmental branches), it is adequately positioned. Intracardiac positioning puts the patient at increased risk for arrhythmia. Distal positioning puts the patient at increased risk of pulmonary infarction or vessel perforation. As a general rule of thumb, the tip of the Swan should be less than 1 cm lateral to the mediastinal border or less than 2.5cm lateral to the descending limb of the line in the SVC.

Ideally, the tip of the IABP is located just proximal to the origin of the left subclavian artery, however this vessel cannot be visualized on X-ray. Therefore, many people use 2 cm below the top of the aortic arch or 2 cm above the carina as appropriate locations for the tip of the IABP. If the IABP is too high, it can occlude the arch vessels and cause brain or limb ischemia. If the IABP is too low, it can occlude the renal and/or mesenteric artery origins and cause end organ ischemia.

A quick Google search will show multiple journal articles claiming sensitivity of Abdominal X-ray anywhere between 50-70% for Small Bowel Obstruction (SBO). Of course, the sensitivity will vary greatly depending on if it’s a single supine view (which is not very helpful) or if the study is an Acute Abdominal Series (which typically includes an upright PA Chest and Abdomen as well as a supine Abdomen film). These studies also do not take into account pre-test probabilities and normal ER or Inpatient workflows. For those reasons, our practical approach to abdominal radiography is as follows: Abdominal X-rays are usually wildly normal or wildly abnormal when it comes to SBO (and most other diagnoses); there’s not too many equivocal Abdominal X-rays for SBO. This is in large part because dilated loops of small bowel can only be seen on X-ray if they are air-filled. Completely fluid-filled, dilated loops of small bowel will not be discernible on X-ray. For this reason, there are many people with SBOs who have normal X-rays (high false negative rate). Therefore, as a general rule of thumb, one should never order a single view abdominal X-ray if there is concern for an SBO. An Acute Abdominal Series or a 2 view Abdominal X-ray (typically Frontal and Upright vs Lateral Decubitus views) can be a good starting point if obstruction is low on the differential and a normal exam will not warrant a CT Abdomen and Pelvis. If the patient is high risk for SBO (history of prior obstructions, multiple prior abdominal surgeries, Crohn’s disease, gastric bypass patient etc.) then CT may be a better initial/final exam since a normal X-ray would lead to a CT anyways. And, in the low risk patient group, all equivocal and abnormal X-ray results would proceed to a CT to determine the cause of the obstruction.

It depends on whether or not the ovary in question is normal appearing on CT. The most common and sensitive sign for Ovarian Torsion on Ultrasound and CT is asymmetric enlargement. Therefore, if one of the ovaries is enlarged on CT, torsion is not excluded and Ultrasound Pelvis is recommended to evaluate the integrity of the blood supply. Additionally, if there is any fluid or inflammatory change around the ovary in question, torsion cannot reliably be excluded by CT. From a practical standpoint, if the primary concern is for Ovarian Torsion, then Ultrasound Pelvis is the best starting exam. If the CT has already been performed and the ovaries are normal and symmetric in size without adjacent ovarian fluid or inflammatory change, then the CT effectively rules out Ovarian Torsion. Sometimes the diagnosis of Ovarian Torsion is made on the initial CT and the patient may be taken directly to laparoscopy without preoperative Ultrasound as the additional imaging exam would only delay treatment. This is our expert opinion. A small case series published in 2014 in the European Journal of Radiology has also come to a similar conclusion. Please click here for more information.

Although this is common practice in nearly every ICU, it is not necessary for most patients. Certainly patients with clinical worsening or a new tube/line insertion warrant a portable Chest X-Ray. It is also typically appropriate in new patients admitted to the ICU to establish a baseline. However, stable patients without a change in clinical status do not require daily Chest X-Rays. The above information is in agreement with current American College of Radiology (ACR) Appropriateness Criteria https://acsearch.acr.org/docs/69452/Narrative/.

Lung Cancer Screening (with Low-dose CT Chest Without IV Contrast) is recommended for patients 50 to 80 years old who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years. The above information is in agreement with current American College of Radiology (ACR) Appropriateness Criteria.

NO. An Ultrasound Abdomen With Doppler is an exam tailored to image the abdominal vasculature (IVC, Aorta, Hepatic Veins, Portal Vein, Splenic Vein, Hepatic Artery, Splenic Artery, SMA origin and Celiac Trunk origin) which does not change with NPO status. The main dietary consideration for abdominal ultrasound is for an Ultrasound of the Right Upper Quadrant looking for Cholecystitis. If the patient has recently eaten a meal (within ~4hrs), they probably don’t have Acute Cholecystitis and the gallbladder will be collapsed as it has excreted its contents to help digest the food. If the patient hasn’t eaten in >24hrs (ICU/Intubated patients), the gallbladder will be distended and Acalculous Cholecystitis may be difficult to exclude based on imaging alone. In general, NPO status recommendations with respect to imaging and procedures is done to minimize the risk of aspiration during the exam or procedure. Only in specific and rare instances does the physiologic process of digestion impact the exam.

It is recommended that patient fast for 4 hrs prior to an MRI Abdomen. Fasting is preferred as there is less gastric distension and GI motility. This could theoretically create motion degradation of the MRI images. However, if the patient has eaten prior to this, it typically does not affect the image quality and our recommendation is to scan the patient without making him or her wait the full 4hrs. The only situation where image quality would be compromised is if an MRCP is to be performed with the MRI. An MRCP sequence is comprised of heavily T2 weighted images which are extremely fluid sensitive. The MRCP images may be non-diagnostic if there is a significant amount of fluid in the stomach and proximal small bowel as this will obscure the small amount of fluid in the biliary and pancreatic ductal systems.

Rectal contrast is ideal for staging Colorectal Cancer on MRI. It is not absolutely necessary however and most cases will be adequately staged without the administration of rectal contrast, particularly if there has been a good pre-imaging colon prep (similar to colonoscopy). Rectal contrast is not routinely administered for cancer staging at some institutions. The utility of rectal contrast is to distend the bowel and help characterize the depth of colorectal wall invasion by the cancer.

No. The standard CT Trauma Body Protocol (CT Chest, Abdomen, and Pelvis With IV Contrast) is sufficient to exclude GI trauma in almost all cases. Some institutions administer rectal contrast as part of their routine trauma CT protocol for high velocity trauma patients, however this is unnecessary as it delays care, increases cost, and is uncomfortable for patients. If there are truly equivocal findings on the initial CT with just IV Contrast, then Rectal Contrast or Oral Contrast can be administered and the patient can be re-scanned.

Yes. Oral CT Contrast in the GI tract should not significantly alter the diagnostic accuracy of an MRI Pelvis or MRI Abdomen. The only situation where image quality may be compromised is if an MRCP is to be performed with the MRI. An MRCP sequence is comprised of heavily T2 weighted images which are extremely fluid sensitive. The MRCP images may be non-diagnostic if there is a significant amount of fluid in the stomach and proximal small bowel as this will obscure the small amount of fluid in the biliary and pancreatic ductal systems.

Typically these are no clinical significance and often found incidentally. They are most commonly Jejunal – Jejunal and considered normal if

This does not mean Sarcoidosis. This wording is reserved for small scattered calcifications in the liver, spleen, and/or mediastinal lymph nodes secondary to a remote prior infection. The infectious organism is typically Histoplasmosis or Coccidioidomycosis. Histoplasmosis is endemic to the Mississippi and Ohio River valleys and Coccidiomycosis is endemic to the Southwest. This is an incidental finding which does not require further work up.

CT Enterography is the same thing as a CT Abdomen and Pelvis With IV and Oral Contrast except that it uses a a neutral or negative oral contrast agent (often VoLumen which is a very dilute Barium/Water solution) that distends the small bowel and allows for better detection of subtle mucosal enhancement. This is almost exclusively used in Crohn’s Disease work ups. The neutral/negative oral contrast agent looks like water on CT rather than the bright white routine oral contrast used in other CTs of the abdomen and pelvis which would mask the mucosal enhancement. If agents like VoLumen are not available, Oral Water can be used as a substitute.

Pulmonary Embolisms (PE)s can sometimes be seen on a routine CT Chest With IV Contrast. The degree of opacification of the pulmonary arterial tree with IV Contrast on routine chest CTs is highly variable and depends on the contrast bolus timing and multiple other physiologic factors which affect the cardiac output. Intense, complete arterial opacification is required to evaluate for filling defect i.e. pulmonary emboli. Therefore, in most cases, the pulmonary arteries are suboptimally opacified/evaluated on the routine CT Chest With IV Contrast. As a general rule of thumb, only large central PEs (located in the main PA, right/left PA branches, and proximal lobar branches) can be adequately excluded on a routine CT. Segmental PEs can sometimes be excluded if the contrast bolus for the CT happens to be timed well for the PAs. Subsegmental PEs are not excluded with a routine CT and will require a CTA Chest With IV Contrast (PE Protocol). In short, typically only large central PEs can be excluded on a routine CT Chest With IV Contrast. A Noncontrast CT is inadequate and cannot exclude a PE.

If the patient has already received a routine CT Chest With IV Contrast and there is concern for an Aortic Dissection in retrospect, repeating a CTA Chest With IV Contrast (Dissection Protocol) is almost always unnecessary. This is particularly true when the clinical suspicion is already low. A phone call to the radiologist for a second look at the aorta is adequate and can exclude the vast majority of dissections with high confidence. Note that tiny, subcentimeter intimal flaps may not be resolved on the routine CT and those will require a dedicated dissection protocol CTA. A Noncontrast CT is inadequate and cannot exclude an Aortic Dissection. A CTA should be ordered if a dissection is suspected in retrospect/after a noncontrast exam. The above logic can be similarly applied to Abdominal Aortic and Iliac Dissections. Mesenteric and Renal Artery Dissections will require a CTA.

When ordering pelvic ultrasounds, a TA + TV ultrasound is almost always the best order. Rarely is one indicated without the other. A TV US without a TA US may be used in select cases to follow up something that was clearly seen on the prior TV portion of the exam and follow up of that abnormality was recommended i.e. follow up uterine fibroids, follow up endometrial stripe thickness, or follow up ovarian cyst. A TA US without a TV US may be used in select cases, most commonly if the patient is not sexually active or for Obstetric ultrasounds in the 2nd and 3rd trimesters. The reason to order both exams is two-fold, one technical and one practical. Practically speaking, a TV US provides far superior images to a TA US because the probe is much closer to the pelvic organs. It often identifies pathology that is not well visualized transabdominally. Most pelvic ultrasound reports are based solely on the TV images and the TA images are only given a cursory look. However, it is not uncommon for an ovary to be seen only with the TA view and be obscured by bowel gas on the TV view. Additionally, very large uterine or ovarian cysts/masses can only be imaged in their entirety with the TA portion of the exam as the TV probe has a smaller limited field of view than the TA probe. Therefore, it is best to have both exams so that the TA can be a backup to the TV US if the TV images are inadequate. This begs the question, why not order both and start with a TV US and then do a TA US only if necessary so that the patient is only charged for one exam? This is the technical point of the answer. For a TA US, the bladder is the acoustic window for the ultrasound beam and must be full to perform the exam. For a TV US, the bladder is emptied so it doesn’t push away the pelvic organs out of the field of view. Therefore, if the TV US is performed first and an ovary or other structure cannot be visualized, then the TA portion of the exam is lost because the bladder has already been emptied. The patient must then return at a later date to finish the TA portion of the exam when the bladder has had time to refill. That is why a TA US is always performed prior to a TV US and they are almost always ordered together. Also, rarely some patients cannot tolerate the TV US and so it’s useful to have the TA images as those images are better than no images.

In general, if the indication is to evaluate for Tumor/Mass, Infection, or a Vascular Malformation, then IV Contrast is recommended. A CT Head Without Contrast is appropriate for almost every other indication.

In general, if the indication is to evaluate for Tumor/Mass, Infection, Demyelination/MS, or a Vascular Malformation, then IV Contrast is recommended. An MRI Brain Without Contrast is appropriate for almost every other indication.

In general, if the indication is to evaluate for Tumor/Mass, Infection/Epidural Abscess, Demyelination/MS, or a Vascular Malformation, then IV Contrast is recommended. An MRI Spine Without Contrast is appropriate for almost every other indication. With respect to the Lumbar Spine, IV Contrast is often administered in patients who have had prior surgery. IV Contrast is always helpful in patients who have had lateral recess instrumentation/microdiscectomy. IV Contrast is typically not helpful in patients with anterior or posterior fusion hardware, laminectomy (without microdiscectomy), or interspinous spacer device placement without microdiscectomy. Without IV Contrast, it can be difficult to differentiate between a Recurrent Disc Herniation and normal postoperative Granulation Tissue. If there is a post-surgical patient without operative notes or a reliable history, then an MRI With and Without IV Contrast is recommended.

No. With modern CT scanners, the Body CT (CT Chest or CT Abdomen and Pelvis) is adequate to characterize spinal lesions/fractures and a dedicated CT of the Lumbar or Thoracic Spine does not provide much more diagnostic value.

Imaging cannot answer this question. It is a clinical decision to intubate a patient.

MRA imaging of the Brain and Neck can be ordered without IV contrast making it the best exam choice for this clinical scenario. CTA imaging necessitates the use of IV contrast and may not be appropriate in patients with Renal Insufficiency.

No. The CT Chest includes diagnostic imaging of the Thoracic Spine. Similarly, a CT Abdomen and Pelvis includes diagnostic imaging of the Lumbar Spine.

No. The CT Abdomen and Pelvis includes diagnostic imaging of the Lumbar Spine. Similarly, a CT Chest includes diagnostic imaging of the Thoracic Spine.

While CTA is more sensitive than CT for Acute Stroke, CTA is also more costly, delivers more radiation, and is more time consuming than a CT. If there are no focal neurological deficits on physical exam, then the pre-test probability of a positive CT or CTA is significantly diminished and MRI Brain Without Contrast will ultimately be needed to exclude Acute Stroke. Therefore, for these patients, a screening CT Head followed by an MRI Brain would best serve the patient and the medical system since the CTA will likely be negative for stroke. On the contrary, people have argued that CTA Head and Neck should be a more routine part of stroke work ups since there is anecdotal evidence for uncommon acute stroke presentations being identified and treated faster because they were found unexpectedly on CTA. Furthermore, the cost of untreated Acute Stroke may justify the routine use of CTA as an initial exam. This approach is complicated however because incidental/asymptomatic brain aneurysms (estimated to be present in ~3% of the general population) found on unnecessary CTAs leads to additional resource utilization in the form of follow up imaging as well as potentially devastating treatment complications, from aneurysm coiling or clipping, for an incidental finding that may never have negatively manifested itself during the patient’s lifetime. In my opinion, CT followed by MRI should be used in patients who have no focal neurological deficits on physical exam. CTA should be reserved for patients with higher NIHSS scores since it is not uncommon for patients with low NIHSS scores to have a normal CT/CTA and then have an MRI which is positive for small volume acute infarction secondary to distal/small vessel occlusion. Moreover, this approach would not change patient management with respect to endovascular vs IV therapy. The decision to give IV tPA can be made after the CT Head, once Intracranial Hemorrhage has been excluded. And, since infarcts which are occult on CT and CTA typically involve small/distal vessels, these patients would not be considered for endovascular therapy anyways.

The short answer is NO, but there are multiple points to consider with this question. X-rays can sometimes diagnose acute sinusitis by visualizing air-fluid levels. They are extremely unreliable however and are frequently normal in many cases of Acute Sinusitis and therefore not recommended. In the non-ICU setting, Acute Sinusitis does not typically present a diagnostic dilemma for the frontal and maxillary sinuses as pain with palpation and clinical history can secure the diagnosis. Acute Sphenoid Sinusitis cannot be palpated and is typically why a CT is performed. In the ICU population, there is a high baseline incidence of sinus opacification which significantly reduces the specificity of imaging. This is predominantly due to the presence of NGTs and/or ETTs (Endotracheal Tube) which cause retention of fluid in the pharynx and sinuses. Therefore, the presence of sinus opacification in these patients should be interpreted with caution as it may be physiologic rather than pathologic.

Papilledema is caused by increased intracranial pressure (ICP) which can produce findings on MRI such as enlargement of the optic nerve sheath, flattening of the posterior sclera, protrusion of the optic papilla into the globe, and tortuosity of the optic nerve. These findings can be very subtle and are not always present when there is increased ICP. In fact, many patients with Idiopathic Intracranial Hypertension (also known as Pseudotumor Cerebri) have completely normal MRIs. MRI is not performed to diagnose or confirm papilledema as it is much more expensive and may be less sensitive than fundoscopy or ultrasound. It is typically performed after fundoscopy to work up the etiology of the increased ICP (tumor, hemorrhage, venous sinus thrombosis/stenosis, etc.), not to confirm papilledema. Even if MRI signs of papilledema exist, fundoscopy is still performed to confirm the MRI findings. Essentially, Fundoscopy and MRI are complementary exams and the MRI is predominantly done to exclude other causes of increased ICP before an LP and/or diagnosing Idiopathic Intracranial Hypertension.

STEALTH Protocol CT and MRI imaging is nondiagnostic and used solely for the purposes of presurgical planning + intraopertaive surgical navigation. The most common indications include Stereotactic Radiosurgery or Stereotactic Biopsy of brain lesions. ENT Surgeons also use STEALTH Protocol CTs to assist with endoscopic sinus surgery. A STEALTH CT SInus is most commonly used in revision sinus surgery or nasal polyposis given the underlying anatomical distortion.

If the indication is to evaluate for Trauma/Fracture, no IV Contrast is necessary. If the indication is to evaluate for Tumor/Mass, Infection, or Vascular Abnormality, then IV Contrast is recommended.

Arthrocentesis is the only definitive test to exclude a septic joint. MRI is sensitive, but not specific i.e. if there is no joint effusion, then a septic joint is extremely unlikely. But, if there is a joint effusion, fluid sampling is the only definitive way to exclude infection.

Yes. An Arthrogram is performed by accessing the joint with a needle and injecting ~ 2 mL of a local anesthetic (commonly Lidocaine) to distend the joint capsule. Next, 1 – 2 mL of a CT Contrast agent is injected to confirm intra-articular positioning of the needle under fluoroscopy. Finally, dilute MRI Contrast solution is injected (~ 10mL for shoulders and hips). 1 – 2 mL of intra-articular CT contrast poses essentially no risk for contrast allergy even if the patient has had a prior anaphylactic reaction to IV CT Contrast. There are a few case reports of patients with anaphylaxis from intra-articular CT contrast, however this is extremely rare and most well-trained musculoskeletal radiologists would not decline the procedure. Furthermore, if the contrast allergy is to IV CT Contrast, the MRI Arthrogram can be performed with just Lidocaine and dilute Gadolinium. Intra-articular CT Contrast is not required to confirm intra-articular instillation of the fluid as this procedure is mostly done by feel/loss of resistance anyways. The arthrogram can also be performed under Ultrasound guidance which does not require CT Contrast. MRI Contrast allergy is rare and most well-trained musculoskeletal radiologists would not decline the procedure if the allergic reaction to IV MRI Contrast was mild or moderate. If the patient has had an anaphylactic reaction to IV MRI Contrast, then a CT Arthrogram may be more appropriate.

For an MRI Arthrogram, intra-articular contrast is instilled to distend the joint capsule. Some structures cannot be adequately evaluated without a distended joint, most commonly the labrum of the hip or shoulder. While labral tears can be seen on non-arthrographic exams, MRI Arthrogram is more sensitive and specific. Arthrography is also useful in evaluating for joint capsular tears, intrinsic wrist ligament tears (Scapholunate, Lunotriquetral, Triangular Fibrocartilage Complex), and Ulnar Collateral Ligament tears of the elbow. In general, if the patient is an athlete or < 40yrs old, MRI Arthrogram should be considered, particularly in the hip and shoulder. In patients > 50yrs old, a routine MRI Without IV or Intra-articular Contrast is almost always the more appropriate test.

Yes, the patient can still get the scan. It is generally recommended that patients abstain from any antacids for 24hrs prior to a DEXA scan. The concern is that theoretically, any undissolved calcium in the GI tract may be picked up on the spine portion of the DEXA scan and produce falsely elevated bone density values. The effect, if any, is likely too small to matter overall however.

A NM V/Q Scan delivers more radiation to the patient compared to a CTA Chest. CTA Chest (PE Protocol) should always be performed over a NM V/Q Scan if the patient has no contraindications to receiving IV CT Contrast. CTA Chest (PE Protocol) also has greater sensitivity and specificity for diagnosing a Pulmonary Embolism.

Since MRI is very motion-sensitive, many children require general anesthesia. Very young or older children may be able to perform an MRI without any anesthesia however. Newborns may be swaddled and scanned while sleeping. Older children who can follow directions, hold still, and cooperate with the MRI technologist throughout the scan may also avoid general anesthesia. There is no age limit to forgoing sedation and it is largely child-dependent. In general, children < 3mo old and > 6 yrs old may be able to avoid general anesthesia with the proper preparation.

Ideally, the tip of the UVC is located at the junction of the right atrium and IVC at ~T8-T9.

The UAC can be placed in a high-optimal or low-optimal position. High-optimal positioning is in the descending thoracic aorta, between T6 to T10. Low-optimal positioning is in the distal abdominal aorta, between L3 to L4.

Yes, we routinely scan pediatric patients with a few caveats. The patient must be old enough to cooperate with our staff to perform the imaging exam. X-ray and Ultrasound do not have a strict cut off for age and the decision to scan pediatric patients is done on a case by case basis at the discretion of the technologist. Pediatric patients who require advanced imaging such as CT or MRI are typically 8 years of age or older.

Starting screening age and modality depend on the woman’s lifetime risk of breast cancer. The current American College of Radiology (ACR) guidelines are as follows: For women at average risk for breast cancer, annual Digital Mammography (DM) screening should start at age 40. For women with genetics-based increased risk (and their untested first-degree relatives) or with a calculated lifetime risk of 20% or more, DM, with or without Digital Breast Tomosynthesis (DBT), should be performed annually beginning at age 30. For women with histories of chest radiation therapy before the age of 30, DM, with or without DBT, should be performed annually beginning at age 25 or 8 years after radiation therapy, whichever is later. For women with genetics-based increased risk (and their untested first-degree relatives), histories of chest radiation (cumulative dose of 10 Gy before age 30), or a calculated lifetime risk of 20% or more, breast MRI should be performed annually beginning at age 25 to 30. For women with personal histories of breast cancer and dense breast tissue, or those diagnosed before age 50, annual surveillance with breast MRI is recommended. For women with personal histories not included in the above, or with ADH, atypical lobular hyperplasia, or LCIS, MRI should be considered, especially if other risk factors are present. All women, especially black women and those of Ashkenazi Jewish descent, should be evaluated for breast cancer risk no later than age 30, so that those at higher risk can be identified and can benefit from supplemental screening. The above information was obtained from the ACR website. For more information, please click here.

No. Mammography during pregnancy is generally safe and the radiation is considered negligible for both the patient and the fetus. However, it is recommended that patients postpone their Screening Mammogram until after pregnancy. This recommendation is for Screening Mammograms only and not Diagnostic Mammograms. Diagnostic Mammograms are performed to evaluate a specific breast problem such as a palpable lump.

Yes. Mammography during pregnancy is generally safe and the radiation is considered negligible for both the patient and the fetus. Depending on the clinical situation, a Diagnostic Ultrasound may be performed first or as a stand-alone exam. Mammography is only done if absolutely necessary, and again, can be safely performed during pregnancy.

Yes. However, typically Screening Mammography is postponed until ~ 3mo after the patient finishes breastfeeding. This is because the milk and hypertrophied glandular tissue increases the breast density and can obscure underlying breast pathology. If the patient is considered to be in a high risk group for breast cancer or is over 40yrs of age and has not had a Screening Mammogram in several years, it may be appropriate to proceed with screening mammography. This decision is made between the patient and provider after a thorough discussion of the risks and benefits of mammography while breastfeeding. The risk is not radiation-related. It is related to the lower diagnostic yield of the screening mammogram while the patient is breastfeeding. Diagnostic Mammograms are safely and routinely performed while patients are breastfeeding. Most commonly, these are done for a new, palpable breast lump. Unlike Screening Mammography, Diagnostic Mammograms should not be delayed while breastfeeding. As a technical consideration, it is recommended that the patient pump or breastfeed ~ 30min prior to the mammogram to prevent expressing breast milk onto the machine during the exam. It will also increase the diagnostic yield of the exam by decreasing the breast density.

The mammogram does not affect breast milk in any way. It will not decrease milk production, and it is completely safe to breastfeed the baby immediately after the patient is done with the exam.

When ordering pelvic ultrasounds, a TA + TV ultrasound is almost always the best order. Rarely is one indicated without the other. A TV US without a TA US may be used in select cases to follow up something that was clearly seen on the prior TV portion of the exam and follow up of that abnormality was recommended i.e. follow up uterine fibroids, follow up endometrial stripe thickness, or follow up ovarian cyst. A TA US without a TV US may be used in select cases, most commonly if the patient is not sexually active or for Obstetric ultrasounds in the 2nd and 3rd trimesters. The reason to order both exams is two-fold, one technical and one practical. Practically speaking, a TV US provides far superior images to a TA US because the probe is much closer to the pelvic organs. It often identifies pathology that is not well visualized transabdominally. Most pelvic ultrasound reports are based solely on the TV images and the TA images are only given a cursory look. However, it is not uncommon for an ovary to be seen only with the TA view and be obscured by bowel gas on the TV view. Additionally, very large uterine or ovarian cysts/masses can only be imaged in their entirety with the TA portion of the exam as the TV probe has a smaller limited field of view than the TA probe. Therefore, it is best to have both exams so that the TA can be a backup to the TV US if the TV images are inadequate. This begs the question, why not order both and start with a TV US and then do a TA US only if necessary so that the patient is only charged for one exam? This is the technical point of the answer. For a TA US, the bladder is the acoustic window for the ultrasound beam and must be full to perform the exam. For a TV US, the bladder is emptied so it doesn’t push away the pelvic organs out of the field of view. Therefore, if the TV US is performed first and an ovary or other structure cannot be visualized, then the TA portion of the exam is lost because the bladder has already been emptied. The patient must then return at a later date to finish the TA portion of the exam when the bladder has had time to refill. That is why a TA US is always performed prior to a TV US and they are almost always ordered together. Also, rarely some patients cannot tolerate the TV US and so it’s useful to have the TA images as those images are better than no images.

Drains typically cannot be placed in fluid collections less than 3cm in size. Collections this size or smaller are usually managed clinically or can be aspirated under ultrasound guidance if fluid sampling vs decompression is required. Additionally, drains are usually placed using CT guidance in the axial plane and therefore, any overlying bowel, vascular or solid structure in the axial plane can prevent drain placement.

It depends on the specific type of procedure and its associated bleeding risk (Low-risk vs High-risk). The Society of Interventional Radiology (SIR) has consensus guidelines for patients undergoing Percutaneous Image-Guided Procedures. Please click here and refer to Table 3.

It depends on the specific type of procedure and its associated bleeding risk (Low-risk vs High-risk). The Society of Interventional Radiology (SIR) has consensus guidelines for Periprocedural Coagulation Parameters. Please click here and refer to Tables 3 and 4 for recommended acceptable periprocedural INR, Platelet, and aPTT values.

It depends on the specific type of procedure and its associated bleeding risk (Low-risk vs High-risk). The Society of Interventional Radiology (SIR) has consensus guidelines for Periprocedural Anticoagulation Medication Management. Please click here and refer to Table 6 for recommendations about when to withhold, thresholds to reverse, and when to restart anticoagulation.

It is not uncommon for tunnelled central lines to back-bleed through the superficial soft tissue tract after placement. First, make sure the line is appropriately positioned (venous instead of arterial) with an x-ray or ultrasound. Next, assuming that the line is venous and that prolonged pressure has failed to stop the bleeding, there are few options. 1) A purse-string suture can be placed around the catheter exit site and will tamponade the bleed. These sutures need to be removed within a few days to prevent damage to the skin. 2) Gelfoam can be placed into the tract (either in whole or slurry form) to create hemostasis. 3) Surgicel can be placed into the tract to create hemostasis.

Pulmonary Embolisms (PE)s can sometimes be seen on a routine CT Chest With IV Contrast. The degree of opacification of the pulmonary arterial tree with IV Contrast on routine chest CTs is highly variable and depends on the contrast bolus timing and multiple other physiologic factors which affect the cardiac output. Intense, complete arterial opacification is required to evaluate for filling defect i.e. pulmonary emboli. Therefore, in most cases, the pulmonary arteries are suboptimally opacified/evaluated on the routine CT Chest With IV Contrast. As a general rule of thumb, only large central PEs (located in the main PA, right/left PA branches, and proximal lobar branches) can be adequately excluded on a routine CT. Segmental PEs can sometimes be excluded if the contrast bolus for the CT happens to be timed well for the PAs. Subsegmental PEs are not excluded with a routine CT and will require a CTA Chest With IV Contrast (PE Protocol). In short, typically only large central PEs can be excluded on a routine CT Chest With IV Contrast. A Noncontrast CT is inadequate and cannot exclude a PE.

If the patient has already received a routine CT Chest With IV Contrast and there is concern for an Aortic Dissection in retrospect, repeating a CTA Chest With IV Contrast (Dissection Protocol) is almost always unnecessary. This is particularly true when the clinical suspicion is already low. A phone call to the radiologist for a second look at the aorta is adequate and can exclude the vast majority of dissections with high confidence. Note that tiny, subcentimeter intimal flaps may not be resolved on the routine CT and those will require a dedicated dissection protocol CTA. A Noncontrast CT is inadequate and cannot exclude an Aortic Dissection. A CTA should be ordered if a dissection is suspected in retrospect/after a noncontrast exam. The above logic can be similarly applied to Abdominal Aortic and Iliac Dissections. Mesenteric and Renal Artery Dissections will require a CTA.

Aortic pathology such as dissections and leaking aneurysms are high-stakes/life or death diagnoses to make. Therefore, it is most often the case/appropriate to sacrifice the kidneys in an ESRD patient or treat the contrast reaction in an allergic patient to make the diagnosis of dissection/rupture using a CTA With IV Contrast. There is some nuance to this scenario however. Ultrasound can be used to diagnose an Abdominal Aortic Aneurysm (AAA) rupture, but is not sensitive for a pending rupture/leaking aneurysm. It is also not very sensitive for dissections. If the patient has an Anaphylactic Allergy to IV CT Contrast, then they can get an MRI and MRA of the Chest +/- Abdomen/Pelvis With and Without IV Contrast to diagnose the aortic pathology. This is provided that they are in stable condition and an MRI machine is available. If the patient has a mild or moderate allergy (really any other allergy besides anaphylaxis) to IV CT Contrast, then it is typically more appropriate to get the CTA and treat the reaction rather than do the MRI/MRA as the MR imaging is much more time consuming and expensive. If the patient has ESRD with very low renal function (Oliguric), then IV CT Contrast may make them Anuric/completely dialysis dependent. In this scenario, an MRI and MRA of the Chest +/- Abdomen/Pelvis With and Without IV Contrast is the best exam using a Group 2 gadolinium-based agent. The Group 2 agent negates the risk of Nephrogenic Systemic Fibrosis (NSF). If a Group 2 gadolinium-based agent is unavailable, then a Noncontrast MRI and MRA can be performed, however, this should only be considered in patients who are stable and if the clinical suspicion of a Dissection/Leaking Aneurysm is low. Noncontrast MRAs are limited in evaluating ascending aortic/aortic root pathology due to cardiac motion. Additionally, small subcentimeter dissection flaps can easily be missed on an MRA as it does not have the spatial resolution of a CTA. Therefore, in cases where the suspicion is high, a CTA with sacrifice of the kidneys is usually the better choice. If the patient is completely dialysis dependent (Anuric) and does not have a functioning renal transplant, there should be no hesitation to administer IV CT Contrast.

The Morphology portion of the exam includes ECG-gated MRI sequences angled along the short and long axis’ of the heart to demonstrate the cardiac structure and anatomy. The Function portion of the exam predominantly evaluates the Left Ventricle and provides values such Ejection Fraction, End Diastolic Volume, End Systolic Volume, Stroke Volume, and Left Ventricular Mass.

Flow-Velocity Mapping is used to quantify through-plane bloodflow. The most common indications include quantification of: Intracardiac shunts (ASD, VSD, PDA, PAPVR and etc.), Regurgitant volumes in valvular disease, and Transvalvular pressure gradients (Aortic Stenosis, Pulmonic Stenosis, etc.).

Gastrografin is a water-soluble oral contrast agent and is typically the best choice for most patients. Gastrografin is ideal for ruling out hollow viscus perforations because it can be readily absorbed by the body if an esophageal/gastric/bowel leak is present. The downside of Gastrografin is that if it is aspirated, it can cause a severe Chemical Pneumonitis. Barium is not water-soluble and is the best oral contrast agent if there is concern for a Tracheoesophageal/Bronchoesophageal Fistula or if the patient is at high risk for aspiration. The downside of Barium is that it is not easily absorbed by the body in cases of a leak and can cause an inflammatory reaction with fibrosis.

Oral contrast, while helpful sometimes, is not necessary in most patients. It is not typically recommended in the ER setting because it can delay care. As a general rule of thumb, if the patient has a BMI of > 25, Oral Contrast does not increase the diagnostic accuracy of the exam. Oral Contrast is most helpful in stressing bowel anastomoses to assess for anastomotic leak or if the patient is very thin and the internal organs/bowel loops are difficult to separate with just IV Contrast. Or, if IV contrast cannot be administered, oral contrast can be helpful. Consult a radiologist if the patient has complex internal anatomy and you believe that oral contrast would be helpful. Cases to consider for oral contrast administration are as follows: Pediatric Appendicitis. Prior bowel surgery and concern for Native Bowel or Anastomotic Leak/Perforation. Concern for Bowel Fistula. Gastric Bypass. Esophageal Tear. Determining Partial vs Complete Small Bowel Obstruction with serial abdominal X-Rays and/or CTs. G-Tube or drain integrity (contrast injected through tube to assess for leak).

Yes. Approximately 1 – 2% of oral contrast is absorbed through the GI tract therefore there is a theoretical risk for a contrast reaction. If the patient has had a history or a mild or moderate allergic reaction to IV CT Contrast, then routine Oral Contrast can be administered. If the patient has a history of anaphylaxis from IV CT Contrast, then an oral barium solution can be used instead of the routine iodinated oral contrast.

Yes. Oral CT Contrast in the GI tract should not significantly alter the diagnostic accuracy of an MRI Pelvis or MRI Abdomen. The only situation where image quality may be compromised is if an MRCP is to be performed with the MRI. An MRCP sequence is comprised of heavily T2 weighted images which are extremely fluid sensitive. The MRCP images may be non-diagnostic if there is a significant amount of fluid in the stomach and proximal small bowel as this will obscure the small amount of fluid in the biliary and pancreatic ductal systems.

No. The standard CT Trauma Body Protocol (CT Chest, Abdomen, and Pelvis With IV Contrast) is sufficient to exclude GI trauma in almost all cases. Some institutions administer rectal contrast as part of their routine trauma CT protocol for high velocity trauma patients, however this is unnecessary as it delays care, increases cost, and is uncomfortable for patients. If there are truly equivocal findings on the initial CT with just IV Contrast, then Rectal Contrast or Oral Contrast can be administered and the patient can be re-scanned.

Rectal contrast is ideal for staging Colorectal Cancer on MRI. It is not absolutely necessary however and most cases will be adequately staged without the administration of rectal contrast, particularly if there has been a good pre-imaging colon prep (similar to colonoscopy). Rectal contrast is not routinely administered for cancer staging at some institutions. The utility of rectal contrast is to distend the bowel and help characterize the depth of colorectal wall invasion by the cancer.

The exact pathophysiology of Contrast Induced Nephropathy (CIN) is not well understood and there are no great published studies on this entity. “At the current time, there is very little evidence that IV [CT] Contrast material is an independent risk factor for Acute Kidney Injury (AKI) in patients with eGFR >/= 30 mL / min/1.73m2. Therefore, if a threshold for CIN risk is used at all, 30 mL/min/1.73m2 seems to be the one with the greatest level of evidence. Any threshold put into practice must be weighed on an individual patient level with the benefits of administering contrast material.” The above information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information. As a rule of thumb, however, if the patient is not in AKI and the eGFR is > 60 mL/min, then IV CT Contrast can be safely administered. If the patient has an eGFR of between 30-59 mL/min, then IV CT Contrast is usually safe as long as the patient is given IV hydration and does not have multiple other risk factors for CIN such as poor renal perfusion, currently taking nephrotoxic drugs, currently in AKI, or diabetes. And if the patient has an eGFR of < 30mL/min, then IV CT Contrast is typically not administered unless there is physician approval in cases of medical necessity. If the patient is critically ill and has multiple comorbidities (i.e. an ICU patient with Diabetes, CKD and CHF on “pressors”/inotropic support), click here for a CIN Risk Calculator. Please note that the data collected for the study which the calculator is based on comes from a cohort of very ill patients, many of whom had baseline CKD Stage 3 or 4, and may have been in AKI or taking nephrotoxic drugs that the study does not account for. Therefore, this likely overestimates the risk for CIN, particularly if the calculator is used to determine risk in the general population/ER setting.

It depends on the type of MRI Contrast. Group 1 and Group 3 gadolinium agents are contraindicated in patients with Acute Kidney Injury (AKI) or Severe Chronic Renal Disease (GFR < 30 mL/min/1.73 m2) due to the risk of Nephrogenic Systemic Sclerosis (NSF). Group 2 gadolinium agents (MultiHance, Gadovist, Dotarem, Clariscan, and ProHance) have little to no risk of NSF according to recent data. Specifically, a recent systematic review and meta-analysis evaluated the pooled risks of NSF in patients with stage 4 or 5 chronic kidney disease receiving a Group 2 gadolinium-based contrast agent. The authors analyzed 16 studies with 4,931 patients who received Group 2 agents. The pooled risk of NSF was 0% (upper bound of 95% CI 0.07%). Thus, they estimated the per-patient risk of NSF from receiving Group 2 gadolinium-based contrast agents in stage 4 or 5 chronic kidney disease to be less than 0.07%. The American College of Radiology (ACR) permits the use of Group 2 gadolinium agents in patients with advanced kidney disease if the exam is medically necessary and recommends using the lowest dose possible to achieve diagnostic quality imaging. NSF is very rare, even in patients with poor renal function, but it is an irreversible complication of IV MRI Contrast administration where Gadolinium precipitates out of the bloodstream and into the tissues causing multiorgan, multi-system fibrosis. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

IV CT Contrast is an Iodine-based liquid. IV MRI Contrast is a Gadolinium-based liquid.

No. IV MRI Contrast is not nephrotoxic.

The exact access site and caliber required to perform a contrast-enhanced study is patient and exam dependant. But, here are some general guidelines: The more central the site of IV access and the larger the caliber of the line, the less risk there is for contrast extravasation. To perform a routine contrast-enhanced CT or MRI, the minimum recommended access is a 22G line in the hand. For a CTA Chest (PE or Dissection Protocol), the minimum recommended access is a 20G line in the mid to upper forearm. For a CTA or MRA of the Head and Neck (Carotids), the minimum recommended access is an 18G line in the right antecubital fossa. Left-sided antecubital fossa access can degrade image quality due to higher rates of venous contamination artifact. Again, the more centrally located and the larger the line, the safer it is for the patient and the better the quality of the exam.

Yes, but only if the central line is power-injectable. Many central lines including PICCs, Ports (also known as Mediports or Port-a-caths), Subclavian lines, and IJ lines are power-injectable. Refer to the manufacturer’s product sheet for this information. Some institutions do not inject through IJ lines due the the risk of Carotid Artery occlusion if there is a contrast extravasation event.

Typically Yes. As long as the patient is not in Acute Kidney Injury (AKI) and has good renal function (~ eGFR > 50) then they can receive another CT bolus without putting them at higher risk for Contrast Induced Nephropathy (CIN). There are no strict maximum allowable doses of IV CT Contrast, in general however, volumes of over 250-300mL in a 24 hour period should be avoided. A typical IV CT Contrast dose is not more than 100mL; so theoretically, a patient with good renal function could receive 3 contrast-enhanced CTs within 24hrs.

The answer is almost always No. It is unclear how IV MRI Contrast will affect the fetus although there is an increased risk of stillbirth/neonatal death. There is also increased risk for a broad set of rheumatological, inflammatory, or infiltrative conditions. There is a potential but not proven risk for Nephrogenic Systemic Fibrosis (NSF). Because it is unclear how IV MRI Contrast will affect the fetus, it should be administered with caution to pregnant or potentially pregnant patients and should only be used if its usage is considered critical and the potential benefits justify the potential unknown risk to the fetus. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes, IV CT Contrast is safe to use in pregnant patients. Animal studies have shown no adverse effects and none have been observed in humans. IV CT Contrast has been reported to have no effect on neonatal thyroid function. Although there is no available data to suggest any potential harm to the fetus from IV CT Contrast, it should be administered only if necessary and after informed consent has been obtained. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes, lactating women who receive IV CT or MRI Contrast can continue breastfeeding without interruption. If the mother remains concerned about any potential ill effects to the infant, she may express and discard the breast milk from both breasts for a period of 12 – 24 hrs. There is no value in stopping breastfeeding beyond 24hrs. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Patients on metformin therapy have the potential to develop metformin-associated lactic acidosis. Since metformin is predominantly excreted by the kidneys, Contrast Induced Nephropathy (CIN) can lead to the build up of metformin and increase the risk of lactic acidosis. Recommendations for metformin use are as follows: “In patients with no evidence of Acute Kidney Injury (AKI) and with eGFR >/= 30 mL / min/1.73m2, there is no need to discontinue metformin either prior to or following the intravenous administration of [CT] contrast media, nor is there an obligatory need to reassess the patient’s renal function following the test or procedure. In patients taking metformin who are known to have acute kidney injury or severe chronic kidney disease (stage 4 or stage 5; i.e., eGFR < 30), or are undergoing arterial catheter studies that might result in emboli (atheromatous or other) to the renal arteries, metformin should be temporarily discontinued at the time of or prior to the procedure, and withheld for 48 hours subsequent to the procedure and reinstituted only after renal function has been re-evaluated and found to be normal.” It is not necessary to discontinue metformin prior to administration of IV MRI Contrast if given in the usual dose range. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

12hr Prep: Methylprednisolone 32 mg PO at 12 and 2 hrs prior +/- Benadryl 50 mg PO at 1 hr prior. 13 hr Prep: Prednisone 50 mg PO at 13, 7 and 1 hrs prior +/- Benadryl 50 mg PO at 1 hr prior. 6hr Prep: Hydrocortisone 200 mg IV at 5 hrs and 1 hr prior and Benadryl 50 mg IV at 1 hr prior. The 6hr Prep can be used in more urgent (ER or Inpatient) situations for which the risk of delaying imaging is greater than the risk for a contrast reaction. Note that the ordering physician assumes a higher risk of a contrast reaction with the 6hr Prep than with the 12hr or 13hr Prep.

Contrast reactions vary in type (Allergic-like vs Physiologic) and severity (Mild, Moderate, Severe). For management of an acute adverse reaction to contrast media in Adults, please click here. For management of an acute adverse reaction to contrast media in Children, please click here. If the patient has a history of a previous allergic-like reaction to IV Contrast, he or she may require corticosteroid premedication prior to performing the contrast-enhanced exam. For a premedication regimen, please see the above question.

In general, if the indication is to evaluate for Tumor/Mass, Infection, or a Vascular Malformation, then IV Contrast is recommended. A CT Head Without Contrast is appropriate for almost every other indication.

In general, if the indication is to evaluate for Tumor/Mass, Infection, Demyelination/MS, or a Vascular Malformation, then IV Contrast is recommended. An MRI Brain Without Contrast is appropriate for almost every other indication.

In general, if the indication is to evaluate for Tumor/Mass, Infection/Epidural Abscess, Demyelination/MS, or a Vascular Malformation, then IV Contrast is recommended. An MRI Spine Without Contrast is appropriate for almost every other indication. With respect to the Lumbar Spine, IV Contrast is often administered in patients who have had prior surgery. IV Contrast is always helpful in patients who have had lateral recess instrumentation/microdiscectomy. IV Contrast is typically not helpful in patients with anterior or posterior fusion hardware, laminectomy (without microdiscectomy), or interspinous spacer device placement without microdiscectomy. Without IV Contrast, it can be difficult to differentiate between a Recurrent Disc Herniation and normal postoperative Granulation Tissue. If there is a post-surgical patient without operative notes or a reliable history, then an MRI With and Without IV Contrast is recommended.

In general, if the indication is to evaluate for Trauma, Tumor/Mass, Infection, or a Vascular Abnormality, then IV Contrast is recommended. Common indications for CT Chest Without Contrast are: Rib Fracture, Pleural Effusion evaluation, Pneumothorax/Pneumomediastinum, Pulmonary Nodule Follow up, and Chronic Dyspnea/Interstitial Lung Disease.

IV Contrast is almost always recommended for CT Abdomen and Pelvis as long as there is no contraindication such as Allergy or Renal Insufficiency. Common indications for CT Abdomen and Pelvis Without Contrast are: Renal Stone and Retroperitoneal Hemorrhage.

If the indication is to evaluate for Trauma/Fracture, no IV Contrast is necessary. If the indication is to evaluate for Tumor/Mass, Infection, or Vascular Abnormality, then IV Contrast is recommended.

A Noncontrast Chest CT is adequate for most chest pathology including pulmonary nodules, masses, edema, and pneumonia. Noncontrast Chest CTs can diagnose pleural effusions but cannot diagnose an empyema unless there is gas in the pleural space, which is a rare finding. Noncontrast Chest CTs are adequate most of the time to evaluate for mediastinal and hilar adenopathy, but a contrast-enhanced exam is far superior as it clearly delineates vessels from nodes and other masses which can be missed on noncontrast exams, particularly in the hilum. Contrast is required to evaluate any vascular pathology in the chest such as Pulmonary Embolism or Aortic Dissection. Contrast is also needed to diagnose Pericarditis. Contrast-enhanced CTs are better at evaluating pneumonia because it can show early necrotizing pneumonia as demonstrated by hypo or non-enhancing pulmonary parenchyma. As a general rule of thumb, any vascular or mediastinal pathology is better evaluated by a CT Chest With Contrast whereas most lung pathology will be adequately evaluated despite the lack of IV CT Contrast.

In general, with the exception of renal stones, IV CT Contrast is ALWAYS preferred and greatly increases diagnostic accuracy. Renal stones, while less conspicuous on post-contrast exams, do not present diagnostic dilemmas and if multiple intra-abdominal pathologies are being considered, one of them being nephrolithiasis, it is better to give IV contrast and provide the radiologist with appropriate history regarding stones as a differential consideration than to perform a noncontrast exam or a CT With and Without Contrast. If IV contrast cannot be administered, then the quality of the exam becomes dependent on how much “intrinsic” contrast the patient has i.e. visceral fat. As a general rule of thumb, if the patient has a BMI > 25, then they will typically have enough visceral fat between organs to allow for accurate diagnosis of pathology. If there is a paucity of visceral fat (pediatric patients), then it becomes much more difficult to diagnose intra-abdominal pathology. This is why most pediatric CTs of the Abdomen and Pelvis include Oral Contrast – to increase the intrinsic contrast/help differentiate bowel from other organs or bowel from a pathological process, such as an abscess (an abscess < 3 cm can easily be mistaken for bowel and missed on a non-contrast exam). Oral Contrast is recommended in patients who cannot receive IV CT Contrast and/or have a BMI < 25. Noncontrast CTs are inadequate in evaluating trauma patients because they can miss solid organ lacerations. Noncontrast Trauma CTs are appropriate if the only concern is for fracture.

No. Patients are never tested for a contrast allergy prior to receiving the contrast agent. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes, they can safely receive IV CT Contrast. Patients with a shellfish allergy are at no greater risk from IV CT/Iodine-based Contrast than are patients with other allergies such as peanuts, soy, etc. Patients with random/unrelated allergies (peanuts, eggs, etc.) are at ~ 2 – 3x increased risk of an allergic-like reaction from IV CT Contrast. However, the risk is modest and having an unrelated allergy such as shellfish should not preclude any patient from having IV CT Contrast. Contrast allergy premedication is also not recommended for these patients. In short, having a shellfish allergy carries essentially no weight in the decision to give or withhold IV Contrast. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes, they can safely receive IV CT Contrast. Patients with a Betadine allergy are at no greater risk from IV CT/Iodine-based Contrast than are patients with other allergies such as peanuts, soy, etc. Patients with random/unrelated allergies (peanuts, eggs, etc.) are at ~ 2 – 3x increased risk of an allergic-like reaction from IV CT Contrast. However, the risk is modest and having an unrelated allergy should not preclude any patient from having IV CT Contrast. Contrast allergy premedication is also not recommended for these patients. In short, having an Iodine/Betadine allergy carries essentially no weight in the decision to give or withhold IV Contrast. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes, they can safely receive IV CT Contrast and/or IV MRI Contrast. Patients with unrelated allergies (peanuts, eggs, etc.) are at ~ 2 – 3x increased risk of an allergic-like contrast reaction. However, the risk is modest and having an unrelated allergy should not preclude any patient from having IV CT Contrast or IV MRI Contrast. Contrast allergy premedication is also not recommended for these patients. In short, having random/unrelated allergies carries essentially no weight in the decision to give or withhold IV Contrast. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

A history of Asthma does increase the risk of an allergic-like contrast reaction, specifically the risk for Bronchospasm. However, the risk is modest and having Asthma should not preclude any patient from having IV CT Contrast or IV MRI Contrast. Contrast allergy premedication is also not recommended for these patients. In short, a history of Asthma carries no weight in the decision to give or withhold IV Contrast. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes. Patients who have had a previous adverse reaction to IV CT Contrast, allergic or otherwise, have a ~ 5x increased risk of developing a future allergic-like reaction if exposed again. A previous reaction to IV CT Contrast is considered the greatest risk factor for predicting a future IV CT Contrast reaction. There is no cross-reactivity between different classes of contrast medium. For example, a prior reaction to Gadolinium-based (IV MRI) contrast does not predict a future reaction to Iodine-based (IV CT) contrast, or vice versa, more than any other unrelated allergy. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes. There is no cross-reactivity between different classes of contrast medium. For example, a prior reaction to Iodine-based (IV CT) contrast does not predict a future reaction to Gadolinium-based (IV MRI) contrast, or vice versa, more than any other unrelated allergy. Patients with unrelated allergies (peanuts, eggs, etc.) are at ~ 2 – 3x increased risk of an allergic-like contrast reaction. However, the risk is modest and having an unrelated allergy should not preclude any patient from having IV CT Contrast or IV MRI Contrast. Contrast allergy premedication is also not recommended for these patients. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes. Patients who have had a previous adverse reaction to IV MRI Contrast, allergic or otherwise, have a ~ 5x increased risk of developing a future allergic-like reaction if exposed again. A previous reaction to IV MRI Contrast is considered the greatest risk factor for predicting a future IV MRI Contrast reaction. There is no cross-reactivity between different classes of contrast medium. For example, a prior reaction to Gadolinium-based (IV MRI) contrast does not predict a future reaction to Iodine-based (IV CT) contrast, or vice versa, more than any other unrelated allergy. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Yes. There is no cross-reactivity between different classes of contrast medium. For example, a prior reaction to Gadolinium-based (IV MRI) contrast does not predict a future reaction to Iodine-based (IV CT) contrast, or vice versa, more than any other unrelated allergy. Patients with unrelated allergies (peanuts, eggs, etc.) are at ~ 2 – 3x increased risk of an allergic-like contrast reaction. However, the risk is modest and having an unrelated allergy should not preclude any patient from having IV CT Contrast or IV MRI Contrast. Contrast allergy premedication is also not recommended for these patients. Allergic reactions to modern Iodine-based and Gadolinium-based contrast agents are uncommon (iodinated: 0.6% aggregate and 0.04% severe; gadolinium-based: 0.01-0.22% aggregate and 0.008% severe). This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Aortic pathology such as dissections and leaking aneurysms are high-stakes/life or death diagnoses to make. Therefore, it is most often the case/appropriate to sacrifice the kidneys in an ESRD patient or treat the contrast reaction in an allergic patient to make the diagnosis of dissection/rupture using a CTA With IV Contrast. There is some nuance to this scenario however. Ultrasound can be used to diagnose an Abdominal Aortic Aneurysm (AAA) rupture, but is not sensitive for a pending rupture/leaking aneurysm. It is also not very sensitive for dissections. If the patient has an Anaphylactic Allergy to IV CT Contrast, then they can get an MRI and MRA of the Chest +/- Abdomen/Pelvis With and Without IV Contrast to diagnose the aortic pathology. This is provided that they are in stable condition and an MRI machine is available. If the patient has a mild or moderate allergy (really any other allergy besides anaphylaxis) to IV CT Contrast, then it is typically more appropriate to get the CTA and treat the reaction rather than do the MRI/MRA as the MR imaging is much more time consuming and expensive. If the patient has ESRD with very low renal function (Oliguric), then IV CT Contrast may make them Anuric/completely dialysis dependent. In this scenario, an MRI and MRA of the Chest +/- Abdomen/Pelvis With and Without IV Contrast is the best exam using a Group 2 gadolinium-based agent. The Group 2 agent negates the risk of Nephrogenic Systemic Fibrosis (NSF). If a Group 2 gadolinium-based agent is unavailable, then a Noncontrast MRI and MRA can be performed, however, this should only be considered in patients who are stable and if the clinical suspicion of a Dissection/Leaking Aneurysm is low. Noncontrast MRAs are limited in evaluating ascending aortic/aortic root pathology due to cardiac motion. Additionally, small subcentimeter dissection flaps can easily be missed on an MRA as it does not have the spatial resolution of a CTA. Therefore, in cases where the suspicion is high, a CTA with sacrifice of the kidneys is usually the better choice. If the patient is completely dialysis dependent (Anuric) and does not have a functioning renal transplant, there should be no hesitation to administer IV CT Contrast.

If the patient has ESRD with very low renal function (Oliguric), then IV CT Contrast may make them Anuric/completely dialysis dependent. If the patient is completely dialysis dependent (Anuric) and does not have a functioning renal transplant, there should be no hesitation to administer IV CT Contrast. They also typically do not require urgent hemodialysis (in contradistinction to a dialysis patient who just received IV MRI Contrast). Patients on dialysis have a theoretical risk from the osmotic load imposed by the IV CT Contrast because they cannot rapidly clear the excess intravascular volume. This osmotic load can theoretically result in pulmonary edema and anasarca. However this is an issue that may have been more significant in the past when high-osmolality IV CT Contrast was used. The bottom line is that unless an unusually large amount of IV CT Contrast (~ 200mL or more) is administered, or there is substantial underlying cardiac dysfunction, there is no need for urgent dialysis after the administration of IV CT Contrast. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Historically, in Oliguric or Anuric patients who were dialysis dependent, IV MRI Contrast was not administered due to the risk of Nephrogenic Systemic Sclerosis (NSF). However, newer Group 2 Gadolinium Based Contrast Agents (GBCAs) are much safer than previous generation Group 1 or 3 GBCAs. Group 2 GBCAs such as MultiHance, Gadovist, Dotarem, Clariscan, and ProHance have little to no risk of NSF according to recent data. Specifically the pooled risk of NSF was 0% (upper bound of 95% CI 0.07%) in patients with stage 4 or 5 chronic kidney disease. The American College of Radiology (ACR) permits the use of Group 2 GBCAs in patients with advanced kidney disease if the exam is deemed medically necessary and recommends using the lowest dose possible to achieve diagnostic quality imaging. We also recommend scheduling dialysis within the same day and after performing the MRI as an additional safety measure. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.

Specifically related to Contrast Induced Nephropathy (CIN), there is no hard and fast rule for when it is safe to give or withhold IV Contrast in patients with a GFR < 30. There is also no predicting who will get CIN. There are plenty of patients with GFRs in the 10 – 15 range who don’t suffer from CIN. There are other patients with GFRs > 20 who will get CIN, but they typically have other risk factors such as Diabetes, may already have some underlying AKI, and are on multiple nephrotoxic drugs. It is the opinion of Rads Consult that CIN is very rare in the absence of active AKI, multiple risk factors for CIN and a severely low GFR. The medicolegal answer is that the exact pathophysiology of Contrast Induced Nephropathy (CIN) is not well understood and that there are no great published studies on this entity. The risk/benefit should be discussed with the patient before proceeding as no one can predict who will get CIN and who will not. “At the current time, there is very little evidence that IV [CT] Contrast material is an independent risk factor for Acute Kidney Injury (AKI) in patients with eGFR >/= 30 mL / min/1.73m2. Therefore, if a threshold for CIN risk is used at all, 30 mL/min/1.73m2 seems to be the one with the greatest level of evidence. Any threshold put into practice must be weighed on an individual patient level with the benefits of administering contrast material.” The above information was obtained from the American College of Radiology (ACR) website. The practical answer is that the need for IV Contrast depends on the type of cancer, it’s presenting pattern of disease and known pattern of metastatic spread. For example, Sarcomas typically recur at the surgical resection site and metastasize to the lungs. No IV Contrast is necessary to screen for lung metastases and local recurrence is monitored with MRI. However, Colon, Renal, and Pancreatic Cancer have a propensity to metastasize to the liver and IV Contrast is necessary to adequately screen the liver for metastatic disease. Primary lung malignancies without mediastinal invasion or solid organ metastatic disease can also be monitored without IV Contrast. Monitoring for nodal disease (in Lymphoma for example) of the chest, abdomen, and pelvis is another example where follow up can be achieved without IV Contrast. In general, if the prevailing pattern of spread/area of concern to monitor is nodal (chest, abdomen, pelvis), pulmonary, or osseous, then a Noncontrast CT is nearly equivalent to a Contrast-enhanced CT. Most other cases require IV Contrast to be considered adequate. The following are some examples that require IV Contrast: Solid organ involvement (primary or metastatic liver disease). If the resection bed or ablation bed is within a solid organ such as Renal Cell Carcinoma after partial Nephrectomy/Ablation therapy or Hepatocellular Carcinoma after Ablation therapy. If there is any invasion of tumor from the primary site into adjacent vessels or organs such as Pancreatic Cancer (this also includes mediastinal invasion from a primary pulmonary malignancy). Nodal disease in the neck (this is much harder to see without IV Contrast than nodal disease in the rest of the body). Oropharyngeal Cancer although monitoring can also be done with PET/CT. Urothelial Cancer (to be done with a CT Urogram protocol to evaluate the mucosal surfaces of the collecting system). Brain, Spine, or Neurogenic tumors require IV Contrast although monitoring is typically done with MRI.

The use of intravenous contrast varies depending on the type of exam requested and the clinical indication. In general, if the indication is to evaluate for Infection, Malignancy, or Vascular Pathology, then IV Contrast is recommended. Common indications for CT Chest With Contrast are: Pneumonia, Empyema, Pulmonary Abscess, Lung Cancer Staging, Mediastinal Mass, Chest Wall Mass, Pericarditis, High Energy Trauma, or vascular pathology such as Pulmonary Embolism, Aortic Dissection, and SVC Syndrome. IV Contrast is almost always recommended for CT Abdomen and Pelvis as long as there is no contraindication such as Allergy or Renal Insufficiency. Common indications for CT Abdomen and Pelvis Without Contrast are: Renal Stone and Retroperitoneal Hemorrhage. For a Head CT or Brain MRI, if the indication is to evaluate for Malignancy, Infection, or a Vascular Malformation, then IV Contrast is recommended. A CT Head Without IV Contrast or MRI Brain Without IV Contrast is appropriate for almost every other indication. For Spine MRI, if the indication is to evaluate for Malignancy, Infection/Epidural Abscess, Demyelination/MS, or a Vascular Malformation, then IV Contrast is recommended. An MRI Spine Without IV Contrast is appropriate for almost every other indication. For extremity/joint imaging, if the indication is to evaluate for Trauma/Fracture, no IV Contrast is necessary. If the indication is to evaluate for Malignancy, Infection, or a Vascular Abnormality, then IV Contrast is recommended.

Typically no. For routine outpatients or ER patients, if a Group 2 Gadolinium Based Contrast Agent (GBCA) is going to be administered, the American College of Radiology (ACR) does not recommend GFR/renal insufficiency screening labs as long as the patient is not on dialysis and is not suspected to be in Acute Kidney Injury (AKI). Group 2 GBCAs such as MultiHance, Gadovist, Dotarem, Clariscan, and ProHance have little to no risk of Nephrogenic Systemic Sclerosis (NSF) according to recent data. Specifically the pooled risk of NSF was 0% (upper bound of 95% CI 0.07%) in patients with stage 4 or 5 chronic kidney disease. This information was obtained from the American College of Radiology (ACR) website. Please refer to the ACR Manual on Contrast Media for more information.