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Applies
to Magnetic Resonance Scan, Head/Spine
Indications
To diagnose intracranial abnormalities including tumors, ischemia,
infection, multiple sclerosis or any abnormalities relating to the brain
or calvarium. MRI is an excellent modality for assessment of congenital
brain abnormalities or relating to the status of brain maturation in the
pediatric population.
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 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. 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??nd 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??ay 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.
