Whittier Imaging: Magnetic Resonance Imaging
MRI is short for Magnetic Resonance Imaging. MRI is an imaging technique used primarily in medical settings to produce high quality images of the inside of the human body. MRI is based on the principles of nuclear magnetic resonance, a spectroscopic technique used by scientists to obtain microscopic chemical and physical information about molecules.
The patient is placed in a tube where various magnetic fields are applied to the body. The way the body responds to those fields and how it relaxes when the magnetic field is removed is noted and sent to a computer along with information about where the interactions occurred. Myriads of these points are sampled and fed into a computer that processes the information and creates an image.
An interesting feature of MRI imaging is that flowing things have a distinctive appearance on MRI scans (similar to Doppler ultrasound). Flowing structures cause "flow voids," which appear as black holes on the scans. There are computers powerful enough to extract information about a given flow void, such as in the carotid arteries in the neck. The computer does this for each and every slice, of which there are many, and it can put together images of the vessel causing the flow void. The images look just like someone had injected dye, as in an angiogram. This is Magnetic Resonance Angiography, or MRA.
The good news about MRA is that it offers another way of looking at vascular structures in the body. For example, in cases where the aorta is injured by arteriosclerosis, aging, or trauma, MRA can provide exquisite images. Resolution can be somewhat of a problem, however, for small structures, such as the carotid arteries. MRA images are good, but the angiogram remains the method of choice for many surgeons who operate on narrowed or blocked arteries.
Face and Neck
MRA -Magnetic Resonance Angiography