1. Safety screening: Before accepting a patient for MRI, do a quick check for the major contraindications (e.g., pacemakers, cochlear implants, and brain aneurysm clips). The technologist must screen for other less frequent contraindications, including metallic foreign bodies in the orbits and certain medical implants. Vena cava filters, especially if nonferromagnetic and remote from the
imaging site, do not generally pose a safety hazard, but they may create artifacts if included in the imaging field.

2. Nephrogenic systemic fibrosis (NSF): If the patient is an inpatient, check the serum creatinine and calculate the glomerular filtration rate (GFR) (visit www. MDRD.com for GFR calculator). If GFR <30 mL per minute, avoid high doses of gadolinium (Gd) and consider noncontrast magnetic resonance angiography (MRA) techniques. Patients in acute renal failure should not receive Gd until the serum creatinine recovers toward normalcy or hemodialysis is instituted. Outpatients should be asked if they are on dialysis or about to begin dialysis. All dialysis patients should have the MR scheduled for just prior (within 24 hours) to the next dialysis treatment session. For patients at risk for NSF, the macrocyclic agents such as Gadobutrol (Gadavist, Bayer, Berlin, Germany), Gadoteridol (ProHance, Bracco, Princeton, NJ) or Gadoterate Meglumine (Dotarem, Guerbet, Bloomington, IN) are safer than the linear agents. Agents with biliary excretion in addition to renal excretion including Gadobenate Dimeglumine (MultiHance, Bracco, Princeton, NJ), Gadexetate Disodium (Eovist, Bayer, Berlin, Germany), and Gadofosveset Trisodium (Ablavar, Lantheus Medical Imaging) also have fewer or no reported cases complicated by NSF. Gadobenate Dimeglumine and Gadofosveset Trisodium are U.S. Food and Drug Administration (FDA)-approved for aorto-iliac MRA. Keep in mind, however, that Gadodiamide (Omniscan, GE Healthcare, Princeton, NJ) has the lowest rate of allergic reactions and may be well suited for patients at risk of allergic reactions and outpatient imaging centers with limited ability to handle a code situation.

3. Clothing: Remove all clothing (including bras) with metallic components such as zippers, snaps, etc. Have the patient wear a hospital gown. Remove hairpins and metallic jewelry. Nonmagnetic gold and silver rings may be worn so they do not get lost, but they should not be near or within the field of interest. If there is a question about safety, metallic paraphernalia should be tested with a small hand magnet.

4. Sedation: Patients with claustrophobia will benefit from diazepam (Valium) 5 to 10 mg by mouth (PO) or lorazepam (Xanax) 1 to 2 mg PO taken 20 to 30 minutes prior to MR scanning. The patient should not be given the sedative until arriving at the scanner in case the facility is behind schedule. Sedated patients need a responsible adult escort to go home.

a. For gadolinium-enhanced MRA (Gd-MRA), a right arm IV access is preferred because this provides the most direct route to the central circulation. It is acceptable to use a small-gauge IV access (minimum 22 gauge or high flow 24 gauge) in the antecubital fossa, hand, or wrist. However, if the IV access is tenuous, consider using a nonionic, low-osmolar Gd contrast preparation to avoid potential pain caused by extravasation of high-osmolar ionic Gd preparations.

b. For hand injection of Gd, use the Smart Set (Topspins, Ann Arbor, MI). This device has a valve mechanism to allow automatic switching from contrast infusion to saline flush without excessive force or risk of breaking connections. It also has the optimum length, caliber, and fittings to allow easy IV injection of contrast by an operator outside the magnet. Caution is urged with power injectors because they are prone to misadministration, extravasation, and a greater risk to the patient in the event of a contrast reaction compared to hand injection because the pump is activated remotely from the control room.

6. Coil selection: Coil selection has to be optimized because the choice determines the available field-of-view (FOV) and the signal-to-noise ratio (SNR)—both of which significantly affect image quality. Because of the complexity of coil selection, many radiologists leave this up to the discretion of the technologist. However, it is important to be aware of the basic coil selection principles because
technologists will generally pick the coil that makes the exam easiest to perform instead of one that produces the highest image quality.

a. Use the smallest possible coil that still covers the anatomy of interest.

b. Choose coils that are used routinely and reliable such as the head, knee, torso, and body coils. Keep in mind that circumferential coils with birdcage construction (head, body, and knee coils) tend to have the most homogeneous sensitivity to MR signal and are unlikely to produce confusing bright or dark spots on the images.

c. When using coil arrays, make sure all elements are working properly. One bad element can reduce vascular signal locally giving the false impression of disease.