Magnetic Resonance Imaging (MRI)
What is magnetic resonance imaging (MRI)?
Magnetic Resonance Imaging (MRI) is a unique tool that constructs cross-sectional pictures of internal organs and structures using radio waves and magnets. MRI technology utilizes a powerful magnet to create a magnetic field that attracts and aligns hydrogen atoms inside the body. Radio wave pulses are then focused on the aligned atoms in a specific organ or body part. These radio signals are returned to a computer which translates them into three-dimensional images that radiologists can use to depict small and hidden structures within organs, blood vessels or joints or to contrast benign and cancerous tissue.
MRI imaging provides a unique view into the interior of the human body and has become an essential tool of modern medical imaging and disease diagnosis. In many cases, MRI provides important diagnostic information that cannot be obtained with other imaging techniques.
MRI is particularly useful for:
- Examining the brain, neck and spinal cord
- Identifying bone and joint damage
- Revealing brain abnormalities in people with Alzheimer’s Disease and dementia
- Helping with the diagnosis of central nervous system disorders, like multiple sclerosis and strokes
- Detecting breast cancer and damage to soft tissues
- Evaluating blood vessels to detect areas of blockage
Main Line Health Imaging utilizes the latest MRI technologies, including powerful 1.5-Tesla MRIs with 8-channel GE EXCITE coils. These machines offer extremely precise and detailed views of the body, aiding in complex diagnoses. And with their shorter tunnel length and less confining space, the new high-field magnets provide a greater degree of patient comfort than older MRI machines.
MRI has proven itself as an invaluable tool for the last 20 years, and Main Line Health Imaging radiologists are confident that advancing technology will find new applications for this important diagnostic resource.
MRI considerations
All MRI imaging requires a high-power magnet as part of the imaging process. People with prostheses, artificial heart valves, implants, or any metal device in their body must notify the MRI technologist before entering the MRI. Under no circumstance should any patient with a pacemaker enter the MRI room. Metalworkers who may have metal fragments in the eyes have a risk of damage to the eyes if a small metal fragment is present, and must have either a plain film or CT scan of the orbits before entering the MRI. Hip prostheses and other imbedded prostheses are usually safe for MRI imaging.
As a precaution, every patient is asked about any metal before entering the MRI. If you have any implant or prosthesis, please have as much information about the implant on hand for your MRI appointment.
State-of- the-art MRI scanners, such as those used at Main Line Health Imaging, must place the magnetic field in very close proximity to the body to create a good quality image. This requires the patient to lie very still on a sliding table. The table is then slid into a narrow, enclosed cylinder where each of the MRI sequences is performed. When the MRI exam is completed, you are slid out of the machine. The entire procedure is painless.
Some people can feel uncomfortable, even in modern short-bore MRI magnets. “Open” MRIs have been developed for this reason. Main Line Health Imaging does have open-bore MRIs at Bryn Mawr Hospital Outpatient Imaging and Paoli MRI for those patients unable to tolerate conventional MRI scanners. In addition, your doctor might prescribe a one-time dose of oral sedation. This dose can do wonders for making you more comfortable and can also reduce motion, which degrades the images.
Most MRI studies can be performed within 20–30 minutes. Some specialized MRI studies or dual studies can take longer. If you think you may need sedation, consult your primary doctor for a prescription for sedation before the examination. It will make your MRI experience much more comfortable.
Do I need to take any precautions when having an MRI?
Magnetic Resonance Imaging is a non-invasive and safe test. As Magnetic Resonance Imaging works with a strong magnet and radio waves, you need to tell us, if anything of the following applies to you or the person that accompanies you into the exam room:
- Aneurysm clip(s)
- Cardiac pacemaker
- Implanted cardioverter defibrillator (ICD)
- Magnetically-activated implant or device
- Electronic implant or device
- Neurostimulation system
- Spinal cord stimulator
- Insulin or infusion pump
- Any type of prosthesis or implant Implanted drug infusion device
- Artificial or prosthetic limb
- Any metallic fragment or foreign body
- Hearing aid
- Any external or internal metallic object
- Cochlear implant or implanted hearing aid
Any metallic substance on you can affect the quality of the diagnostic images. It can also cause discomfort or even injury to you when placed into the metallic field.
Also, tell us if you are pregnant.
How do I prepare for an MRI?
No special preparation is needed prior to the exam, unless your doctor has given you other instructions. You will be asked to complete a safety screening form and answer questions pertaining to your medical history. Please wear loose clothing without zippers or metallic parts. Remove all jewelry, watches, hairpins, glasses, wallets and other metallic objects.
What happens during an MRI scan?
After you have removed all metal objects, the technologist will position you on a special table. Your head will be placed in a padded plastic cradle or on a pillow, and the table will then slide into the scanner. The MAGNETOM Espree 1.5 Tesla Open Bore MRI system makes scanning extremely comfortable and convenient for the patient. Thanks to MAGNETOM Espree's remarkably short 125 cm magnet, over 60 percent typical MRI exams can be done with the patients head outside of the Open Bore. Anyway you will be able to communicate with the technologist during the scan.
For clear pictures, you will be asked to hold very still and relax. In some cases, you will be asked to hold your breath. Any movement, especially of your head or back (even moving your jaw to talk) during the scan will seriously blur the pictures. While the machine is taking your pictures, you will hear rapidly repeating, thumping noises coming from the walls of the scanner, earplugs may be provided. During this time, you should breathe quietly and normally but otherwise refrain from any movement, coughing or wiggling. When the thumping noise stops, you must refrain from changing your position or moving about. This whole procedure will usually be repeated several times, and the entire exam ordinarily takes between 15 and 30 minutes to complete.