MRI of the Head
Alternate Names : Cranial MRI, Head MRI Scan, Magnetic Resonance Imaging - Cranial, MRI - Cranial, NMR - Cranial, Nuclear Magnetic Resonance - Cranial
Definition
An MRI of the head is a non-invasive procedure that uses powerful magnets and radio waves to construct pictures of the clear, detailed pictures of brain tissues.
Unlike conventional radiography and computed tomography (CT), which make use of potentially harmful X-rays passing through a patient to generate images, MRI imaging is based on the magnetic properties of atoms. A powerful magnet generates a magnetic field roughly 10,000 times stronger than the Earth's. A very small percentage of hydrogen atoms within the body will align with this field.
The "nuclear" in the original name (now seldom used) refers to the proton in the nucleus of the hydrogen atom and does not imply radioactivity.
When focused short radio wave pulses are broadcast towards the aligned hydrogen atoms in tissues of interest, they will return a signal of their own. The subtle differences in that signal from dissimilar tissues enables the MRI to differentiate between various organs, and potentially, provide contrast between benign and malignant (cancerous) tissue.
Any imaging plane, or "slice", can be projected, and then stored in a computer or printed on film. MRI can easily be performed through clothing and bones. However, certain types of metal in or around the area of interest can cause significant errors in
the reconstructed images. (The errors are called artifacts.)
Pictures & Images
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Why is the Test Performed?
MRI provides detailed pictures of the brain and nerve tissues from multiple planes without obstruction by overlying bone. In fact, about 90% of all MRI scans are for brain or spine disorders.
MRI is the procedure of choice for most brain disorders. MRI is particularly useful in brain and neurologic disorders, because it can clearly show various types of nerve tissue. It provides clear pictures of the brainstem and posterior brain, which are difficult to view on CT scan. It is also useful for the diagnosis of demyelinating disorders (disorders such as multiple sclerosis that cause destruction of the myelin sheath of the nerve).
MRI is a noninvasive procedure that can evaluate blood flow and the flow of cerebrospinal fluid (CSF). MRI can distinguish tumors or other lesions from normal tissues. MRI is sometimes used to avoid the dangers of angiography or of repeated exposure to radiation.
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