MRI, Magnetic Resonance Imaging

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Description of device and procedure, what to expect: 
The MRI machines can be categorized according to Magnetic Field Strength. Low Field units are about .6 Tesla and are suitable for brain and spine imaging. Image quality is not as good as the higher field strength units such as the 1.5 Tesla MRI machines such as the General Electric. The 1.5 Tesla machines give the best image quality and can do very high quality brain and spine imaging as well as excellent orthopedic imaging of the joints. Use of the MRI for chest and abdomen imaging is not very good because of problems with respiratory and cardiac motion which degrades image quality.

There are new MRI machines that have been described as "Open Magnets" , and if you suffer from claustrophobia, the OPEN MRI may be what you need. Otherwise, the standard MRI machines do cause claustrophobia because the patient is placed on a table into a large Magnetic machine which has a rather small diameter bore for the patient’s body. Once in the machine, you will not be able to get out of the machine by yourself, and this feeling of helplessness adds to the claustrophobia which some people find disturbing. In addition, most machines make a loud "knocking" noise from the magnetic coils changing pulse direction. Some patients may benefit from mild sedation with Valium prior to the scan and most centers play music and maintain verbal contact with the patient while they are in the scanner to help them cope with it.

Scan times are rather long, so you can expect to spend 30 to 60 minutes in the MRI Magnet.

The pictures themselves look like axial slices through the anatomic structure. The MRI Computer can reconstruct or "re-slice" the images at any angle. Sagital and Coronal plane images are also commonly done. The MRI images differ from CAT scan images in that the MR images represent magnetic characteristics of body tissues, while CT images show only xray photon attenuation which is similar to atomic density if the biologic tissues. Below are some MRI images of the normal brain:

Contrast material: Intravenous Gadolinium is very safe to use and improves image quality by enhancing the vascular compartment.

Anatomic Areas:
Brain: MRI is excellent for showing abnormalities of the brain such as: stroke, hemorrhage, tumor, infection, multiple sclerosis, demyelinating disease.

Head and Neck: Carotid artery disease, nasopharyngeal tumors, sinus disease.

MRI of the brain for "headache" is almost always negative, but useful because it reassures the patient that there is no underlying disease process.

MRI of the Spine shows: bulging or herniated disk, spinal stenosis, metastatic disease, etc.

Precautions and Contraindications to MRI Imaging: There is a very stong magnetic field which exerts coniderable force on paramagnetic or metal objects and disturbs electronic devices placed in the field. Always check with the MRI technologist in advance if you have any metal objects on or in your body. The magnetic field will erase your magnetic strip informationon your credit cards.

If you have any of these you should not go into the strong magnetic field of the MRI magnet:
1) Cardiac Pacemaker (electronics can be affected by the magnet)
2) Cerebral aneurysm metal clip in the brain (metal can be pulled by the magnetic field)
3) Metal fragments imbedded in the eye or other sites (metal can be pulled by the magnetic field)

The MRI tech will go through these questions with you before the scan.