What is MRI?
MRI (Magnetic Resonance Imaging) has been clinically available since the early 1980's. It is a radiological technique that relies on magnetic spins of protons in the human body to generate images. It is fundamentally different than CT scanning, which uses x-rays to extract information from the human body. Similar to CT scanning, though, is the cross-sectional nature of MRI images, that allows physicians to see "into" the body.
MRI uses no harmful radiation in creating images. Strong magnetic fields and radiofrequency waves (ie, the same wavelength used in conventional radio transmissions) are used to create images, and no known harmful effects have been shown in human beings. The great advantage that MRI brings to medical imaging is its ability to detect differences in soft tissue contrast. This has important applications in imaging of the brain (where, for instance, gray matter and white matter can be easily differentiated from one another), in musculoskeletal imaging (where many injuries involve soft tissues such as ligaments and tendons), and in body imaging.
Please refer to each anatomic location for more detailed information on the use of MRI according to anatomy.
MRI machines come in a few different varieties. The main difference is between "open" and "closed" machines. The open machines are usually "low strength" magnets. These are the machines that you would use if you were claustrophobic. New open MRI machines (like we have in our Montclair and West Caldwell locations) can produce high quality images of almost every area of the body. For "high end" imaging or for dynamic imaging (of the prostate gland or of the breast), the more powerful "closed" MRI is necessary. Two such state-of-the-art closed (or high field strength) MRI machines are in our Nutley and West Caldwell offices.
In December of 2012 a new high-field open MRI (1T) was added in our West Caldwell location. This is a major technological advance, using a superconducting magnet and coil technology unavailable on other open magnets to acquire high-quality images on par with closed high-field strength MRIs in an open environment.
The MRI in Nutley is a state-of-the-art Toshiba Vantage 1.5 T machine. It is one of the shortest of the "closed" machines, such that if your knee is being imaged, your head will be out of the machine. It is also the quietest machine available, Toshiba having put tremendous effort into insulating the machine to make it quieter.
Most importantly, though, is the superb quality of the exams produced on this machine. From neuroimaging to body imaging, our specialty trained radiologists are well versed in the most up-to-date MRI techniques available. Please refer to each individual section to learn more about the amazing diagnostic capabilities of our MRI.
The MRI at Montclair on Park St. is a Hitachi Airis Elite. It is an open-air MRI, affording all of the comfort of open MRI architecture. However, it has powerful gradients, allowing it to create images of mid field strength quality. Whenever scheduling an MRI exam, please be sure to inquire which MRI machine would be right for you.
What to expect
Upon arriving at our office, you will be asked to change into a gown. The MRI technician will ask you to remove all metallic objects, which should not be taken into the MRI room (see MRI Safety). This, of course, includes watches, cell phones, wallets and credit cards, all of which can be damaged by the strong magnetic field in the room. You will already have filled out an MRI Questionnaire, insuring that you have no implantable devices in your body that could be dangerous in the MRI magnet.
You will be placed on the MRI gantry and a surface coil will be placed over the anatomy being imaged. For some exams, an IV line will be placed in order to administer MRI contrast material.
For the rest of the exam, all you have to do is lie in the machine and be as still as possible. Most exams run for approximately 30 minutes or less. For body MRI exams (of the abdomen, liver, kidneys) all imaging must be done during suspended respiration, in order to avoid motion from breathing. For these exams, you will be asked to hold your breath repeatedly. A typical MRI exam consists of 4-6 different pulse sequences. For body exams, these sequences are all tailored to run for a maximum of approximately 20 seconds, enabling you to hold your breath (sequences for non-breath hold exams run up to 5 minutes).
Your exam will be interpreted immediately upon being finished, and a report will be faxed to your doctor, usually within 24 hours (unless your exam was completed after 5:00 pm).
MRI IV Contrast Material
The principle behind the administration of MRI contrast material is exactly the same as that behind CT contrast material, some reactions to gadolinium can occur.
Some MRI exams require an IV injection of contrast material. This is an aqueous solution containing a moiety called Gadolinium, a non-reactive, safe chemical. It is injected through an IV catheter, and is distributed through your bloodstream. It is picked up by all organs, and renders organs more easily seen on MRI scans. Its main use is to allow radiologists to visualize pathologic processes more easily. Imagine an inflamed tissue. That tissue usually has a bigger blood supply than a non-inflamed organ, and it therefore gets more contrast material delivered to it...it is therefore brighter on MRI images. Without the contrast material, many inflamed tissues cannot easily be distinguished from normal tissue. The same is true of malignant (cancerous) tissue...they usually have a more exuberant blood supply than normal tissue, and IV contrast material enables the radiologist to detect them more easily. In fact, some malignancies, if small enough, would be not detectable without IV contrast material.
Gadolinium contrast is very safe. It is distributed in your blood, and is excreted by your kidneys, within minutes of the injection. Gadolinium is safe for the kidneys. In addition, there is extremely low risk of reaction to the compound. If you have had a reaction to CT contrast material, this has no bearing on your ability to tolerate Gadolinium.
MRI contrast is generally avoided in pregnant women, not because of a proven harmful effect on the fetus, but because there has not been sufficient research on potential harmful effects.
If you have any questions about MRI Gadolinium contrast please feel free to talk to one of our radiologists or nurses.
The safety issues of MRI are all based on the MRI machine being a very strong magnet. A standard MRI machine has a magnetic field strength of 1.5Tesla compared to the earth's magnetic field of .00005 Tesla.
No metallic objects should be brought into the MRI room. In fact, only ferromagnetic metals are attracted to magnets, but for safety's sake, all metallic objects of patients are left outside of the room. In addition to attracting ferrometallic objects, the MRI's strong magnetic field will erase credit cards, destroy intricate mechanisms of watches, and ruin electronic devices such as cell phones. Therefore, patients must change into a gown outside of the MRI room.
Certain implantable medical devices are also sensitive to the strong magnetic field of an MRI machine. These include internal pacemakers, certain cochlear implants, and certain prosthetic heart valves. We have manufacturer's lists of acceptable and non-acceptable devices, and it is very important for you as a patient to inform us of any implantable device that you may have. These should be listed on our MRI Intake Sheet, and we will inform you whether they are safe for MRI imaging.
In addition to medical devices, metallic foreign bodies, such as shrapnel from gunshot wounds, or metallic flakes from metal shops, may be present in sensitive places in the body (near the spine or eye). If you have any such metallic foreign bodies, you must let us know about them prior to imaging.
In terms of the safety of MRI imaging itself, the magnetic field radio-frequency pulses that are used in creating MRI images have been shown to be entirely safe for human beings.
Please don't hesitate to inquire further concerning safety issues of MRI imaging.