Summary Of Evidence

N/A

Analysis of Evidence

N/A

Magnetic Resonance Imaging (MRI) is a noninvasive diagnostic imaging modality used to diagnose a variety of central nervous system (CNS) disorders. MRI provides superior tissue contrast when compared to a Computerized Tomography (CT) scan, is able to image in multiple planes, is not affected by bone artifact, provides vascular imaging capability, and makes use of safer contrast media (gadolinium chelate agents). Its major disadvantage over a CT scan is the longer scanning time required for study, making it less useful for emergency evaluations. Contraindications include patients with implanted neurostimulators or cochlear implants. Potential contraindications may include patients with cardiac pacemakers (refer to the CMS Internet-Only Manual, Pub 100-03, Medicare National Coverage Determinations Manual, Chapter 1, Part 4, §220.2), metal fragments in the eye, magnetic ocular implants or patients with older ferromagnetic intracranial aneurysm clips. All of these objects may be potentially displaced when exposed to the powerful magnetic fields used in MRI.

MRI of the orbit, face, and/or neck may be considered medically reasonable and necessary when used to diagnose and characterize pathology of the eye, nasopharynx, oropharynx, and neck including tumors, infection, soft tissue pathologies, and congenital abnormalities. In cases involving trauma to the orbit, face and/or neck, a CT scan is frequently superior to MRI for assessing injury.

MRI is considered investigational when medical records document the service was performed only for one of the following:

• measurement of blood flow and spectroscopy,
• imaging of cortical bone and calcifications, and
• procedures involving spatial resolution of bone or calcifications.

In some instances, ordering a MRI of the brain in addition to a MRI of the orbit, face, and/or neck may be medically necessary on the same day. The medical record should document the medical necessity for these two procedures being performed on the same day.

Initial imaging of the thyroid should be done with ultrasound or nuclear medicine, unless there is a known carcinoma present.