Indications Evaluation of the liver, spleen, pancreas, kidneys, adrenal glands, and the remainder of the upper abdomen. In addition to similar information gained from computed tomography (CT) of the upper abdomen, MRI has been found to be useful in certain instances in differentiating benign from malignant pathology.

Contraindications Patients weighing more than 300 lb and patients unable to squeeze into the magnet cannot undergo MRI. An absolute contraindication for MRI is a cardiac pacemaker. Relative contraindications to magnetic resonance imaging include intracranial aneurysm clips, cochlear implants, insulin infusion and chemotherapy pumps, neurocutaneous stimulators and prosthetic heart valves, depending on date of manufacture and metallurgical composition. Please consult MRI physician if questions arise. Patients who have metallic foreign bodies within the eye or who have undergone recent surgery within the last 6 weeks requiring placement of a vascular surgical clip, should also not undergo MRI. The safety of MRI in pregnant patients has not been determined. In such cases, prior consultation with the MRI physician is required. Generally, patients who have undergone recent surgery not requiring vascular clips or who have had coronary artery bypass surgery in the past may undergo MRI. Patients who have shrapnel wounds or orthopedic prostheses can generally safely undergo MRI unless the metallic device is in the anatomic region to be scanned which results in degradation of the images. Patients with surgically implanted intravascular vena cava filters to prevent pulmonary embolism can usually be scanned if the device has been in place for at least 6 weeks. Patients requiring life support equipment including ventilators require special preparation. Please contact MRI physician ahead of time. Central venous lines, Swan-Ganz catheters, and nasogastric (NG) tubes usually present no problems. If the patient is positive when screened for metallic devices and you are uncertain of their significance, the MRI radiologist will provide additional information to assist you.

Patient Preparation Patients should remain NPO at least 4 hours prior to the exam. Inpatient: Patient must be able to lie quietly while the scan is performed. The patient should be screened for metallic devices by nursing personnel. (See Contraindications.) This includes metal introduced into the patient either surgically or by trauma. All metallic objects must be removed from the patient including jewelry or any other metal objects which may be in the patient's bedding. Please remove dentures or other dental appliances. I.V.s which contain no metal are fine, but infusion pumps must be removed. Oxygen tanks and metallic backboards may come with the patient but will be removed prior to the patient entering the magnet room. Oxygen may be provided in the magnet room. Trauma, ICU, or CCU patients should be accompanied by a nurse. The patient needs to be NPO for abdominal MRI exams. If the patient is restless, combative, or claustrophobic, proper sedation may be administered on the floor prior to the MRI, or at the MRI Center. Consult the MRI radiologists with questions on proper sedation. Outpatient: The patient should be screened for metallic devices. (See Contraindications.) If a question exists as to the patient's suitability for MRI, the MRI radiologist will assist you with your questions. If the patient is claustrophobic, oral or parenteral sedation may be necessary. If so, the patient should be accompanied by another adult to provide transportation home after the examination.

Aftercare If the patient received an MRI contrast agent (Magnevist®) and develops a delayed hypersensitivity reaction (ie, hives or shortness of breath), the referring physician or MRI radiologist should be contacted immediately.

Data Acquired Digital information with film reproduction

Limitations Generally, the greatest limitation of magnetic resonance imaging results from the patient's fear of the procedure. The patient must remain quiet and still for several scans, each lasting from several minutes to 10 minutes in length. Total examination time is usually 30-45 minutes and occasionally up to 1 hour. If the patient is restless during the examination, motion artifacts will be present on the images limiting their diagnostic value. If the patient is claustrophobic, mild oral sedation or occasionally parenteral sedation may be needed. Also the patient can be accompanied by a family member or friend during the examination which helps calm the patient's anxiety in many cases. Patients requiring life support equipment such as ventilators require special preparation. Please refer to Contraindications for further causes for rejection.

Additional Information In some cases, an MRI contrast agent (Magnevist®) may be needed to increase the diagnostic accuracy of the MRI. This contrast agent can be administered to patients with a previous history of allergies to conventional iodinated x-ray agents as it contains no iodine. Contraindications to its use include previous allergy to the contrast agent itself, renal failure, certain types of anemia, and Wilson's disease. The contrast agent is generally very safe and increases the diagnostic efficacy of the MRI. Intramuscular or subcutaneous injection of glucagon may be given to decrease motion artifacts from peristalsis.

References