MRI SCANNERS, or Magnetic Resonance Imaging scanners, like X-rays and CT scanners, are machines doctors use to take pictures of the inside of the body so that they can figure out what’s ailing you.
MRI doesn’t involve ionizing radiation like X-rays and CT scans. Rather, MRI takes advantage of something you already have in your body – water. Another benefit to MRI is its ability to generate three dimensional images in any orientation and at any depth in the body.
While X-rays remain useful for looking at bones, MRI scans are the diagnostic tool of choice for soft tissue – the circulatory system, ligaments, organs and the spinal column and cord. MRIs help physicians identify multiple sclerosis, tumors, tendonitis, strokes and many other conditions. For most applications, MRI is far superior to other imaging tools in providing non-invasive images (and even chemical information) at high resolution.
MAGNETIC FIELD STRENGTH
The strength of the MRI signal is influenced by the “magnetic field strength” of the MRI magnet. The magnetic field strength of an MRI magnet is measured in a unit called the “Tesla (T).” For example, a 1.5 T MRI scanner has a field strength of 1.5 Tesla
1.5T MR vs. 3T: To most physicians and hospitals, 1.5T MR is the most reliable field strength. With a wide variety of coil options, 1.5T has the potential for better image quality across a variety of imaging applications in comparison to 3T. Imaging departments and imaging centers, like Rockledge MRI & PET Center, recognize that 1.5T simply has a more proven track record than its higher field strength cousin, the 3T.
A challenge for higher strength magnets is the interaction with metal implants such as stents, aneurysm clips and even prosthetic devices. With the Siemans 1.5T, Rockledge MRI patients who have these safety concerns are not an issue and imaging can be done without an increase in metal artifact.
“1.5T has now struck upon the highest level upon which you can achieve good imaging for the array of imaging applications, such as abdominal, neuro, cardiac, chest, spine, peripheral, and joint imaging—without one of those groups falling off the map,” according to Alan R. Moody, radiologist in chief, department of diagnostic imaging, at Sunnybrook Health Sciences Centre in Toronto. “The reason 1.5T is so successful is that it works for all of those applications,” he says.
“As you go to the higher field strengths, because of the physics, some of the artifacts that you get start to impact on the image quality that you don’t get at 1.5T and you have to work harder to get your images out at 3T,” adds Moody.
Another limitation of 3T, and thus a benefit of 1.5T, is related to its energy deposition. 3T might enable faster and higher resolution imaging, however, the restriction is in how much energy can be put back into the patient.
“With 3T you have to ease back on the throttle, and you potentially lose some of the advantages you had of ramping up to that field strength in the first place,” Moody says, who adds that there seems to be a slight plateauing of that linear progression of the low field strength. Instead of racing to the next level in magnet strength, the imaging community has hit a plateau, staying strong with 1.5T MRI for its applicability across imaging applications.
SHORT BORE MRI VS. OPEN MRI
Many existing open MRIs are originally designed to accommodate larger or claustrophobic patients. Conventional MR scanners are cylindrical in shape, while an open MRI is usually open on two or three sides. Most claustrophobic patients want to automatically gravitate toward “Open MRI’s” without even considering other options.
While, a patient could use an Open MRI, these systems bring with them a couple of compromises. Scan times are much longer. Additionally, the image resolution offered by these systems can be less than optimal when certain parts of the body (most notably, the brain, vascular, abdominal and spine) are being scrutinized.
“Open MRI” scanners generally have field strengths of 0.2-0.3 T, and are considered to be “low-field” systems. “Mid-field” systems have field strengths of 0.5-1.0 T. “High-field systems” are MRI scanners that operate at or above 1.5 T.
Rockledge MRI & PET Center addressed this issue, with the Siemans Short Bore MRI, and enabled all patients a comfortable solution. Short bore systems are 50 percent shorter and five percent wider than conventional MRI setups.
These altered dimensions make for a much less claustrophobic experience for our patients. Scanning time is the same as with conventional MRIs. Best of all, short bore MRIs offer first-rate image quality with superior resolution.
Now, claustrophobic patients need not compromise. Rockledge MRI also offers oral and IV sedation and a patient may bring their own choice of music-all for added comfort.
ABOUT THE AUTHOR
Dr. Wasim Niazi is a neurologist who has practiced in Rockledge, Florida for the last 15 years. Board Certified in Neurology, Pain Medicine and Electro-diagnostic Medicine, Dr. Niazi also has special interests in epilepsy with video and ambulatory monitoring, PET scan of brain for diagnosis of dementia and Sleep Medicine. Dr. Niazi has privileges at Wuesthoff and Cape Canaveral Hospital. For more information call 321-636-6599 or log on to www.RockledgeMRI.com.