Magnetic resonance Imaging is a non invasive, essentially painless, imaging test which provides an excellent tool in evaluation of a wide range of medical conditions.
MR utilizes a very strong static magnetic field (which is many times stronger than that of the earth's field, measured in Tesla units), as well as radio waves and computer software in order to create a very detailed image of the brain parenchyma, the adjacent soft tissues, bone marrow and essentially any material which contains protons. The images are created without the use of ionizing radiation.
MR allows physicians to better evaluate the brain for disease processes that may not be assessed adequately with other imaging modalities.
Equipment
Two state-of-the-art MR scanners (GE Healthcare), including one 1.5-Tesla scanner and a new powerful 3-Tesla scanner. The stronger magnetic field provides better resolution without prolonging scan time and also allows cutting down in the amount of contrast media without compromising image quality.
Common uses
MRI of the head is the modality of choice in demonstrating:
- Developmental anomalies of the brain
- Subtle changes in the brain parenchyma (for example in metabolic diseases)
- Tumors of the brain (diagnosis and follow up)
- Pituitary gland lesions (e.g adenoma)
- Disorders of the eyes and the inner ear.
- Certain chronic disorders, such as multiple sclerosis.
- Epilepsy- in search of subtle abnormalities and preoperative assessment
- MR Angiogram (MRA), a non invasive technique by which we can demonstrate the arterial vasculature in search for aneurysms and other vascular malformations.
- MR Venogram (MRV), a non invasive study of the venous system for investigating Venous vascular malformations as well as sinus venous thrombosis
- Chemical consistency of a lesion (MRS) for evaluating metabolic disorders and tumor activity
- Functional imaging, to identify eloquent brain areas (responsible for language, vision, sensory and motor activity) as part of preoperative assessment in order to minimize neurological deficits.
- Fetal brain development when ultrasound is inconclusive
- Document brain abnormalities in patients with dementia.
How is the scan performed?
Scans are usually arranged through the Healthcare system ("Kupot Holim").
For this type of study you will be asked to lie on the examination table and be positioned within the scanner opening. The technician will then place a specially designed coil over the part of the body to be investigated. Elastic straps and pillows will help you stay in the correct position. The technician will then advance the bed into the scanner itself which is shaped like a long hollow tube and will leave the room. During the exam the scanner will make very loud rapping noises (like a jackhammer) which will require you to wear ear plugs.
A routine MR scan of the head includes a series of sequences, each lasting a few minutes and may last between 30 and 60 minutes. It is important to hold still as much as possible during the scan in order to avoid blurring of the images.
For some patients, a small intravenous catheter will be placed in their arm to administer a paramagnetic contrast agent, Gadolinium. Please alert the physician or technician if you ever experienced an allergic reaction to contrast.
Are there contraindications to MRI?
Due to the strong magnetic field in the room, it is contraindicated to undergo the study if you have certain metal hardware in your body (i.e. a pacemaker, defibrillator wires, metal implants, cochlear implants, surgical clips in the brain). Pregnant women should not have this exam unless the potential benefit from the MRI is assumed to outweigh the potential risks. In that case, you will be tested in the lower field magnet (1.5 Tesla) and contrast will usually not be administered. Some claustrophobic patients may require pre-medication to relax during the study.
Advantages:
· The MR scan is an ideal tool for demonstrating brain parenchyma with excellent ability to distinguish between different tissue
· There is no ionizing radiation involved.
Drawbacks:
· Long scanning times
· Uncomfortable position and loud noises
· Young children require general anesthesia
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