What is an MRI?
MRI, or magnetic resonance imaging, scan is an imaging test that uses a machine with powerful magnets and radio waves to create pictures of the area between the hip bones (called the pelvic area) with a special focus on the prostate gland, that lies deep within the pelvis. Other structures inside and near the pelvis include the bladder, male/female reproductive organs, lymph nodes, large bowel, small bowel, and pelvic bones.
An MRI does not use radiation. Single MRI images are called slices. The images are stored on a computer or printed on film. One exam produces dozens or sometimes hundreds of images.
Multiparametric MRI (Mp-MRI) is an advanced form of imaging. It uses three MRI techniques to provide anatomical pictures and information on the function of the prostate gland. Mp-MRI assesses water molecule motion (called water diffusion) and blood flow (called perfusion imaging) within the prostate. This helps your doctor tell the difference between diseased and normal prostate tissue.
What are some common uses of the procedure?
Your doctor uses MRI to diagnose prostate cancer and see if it is limited to the prostate. Mp-MRI provides information on how water molecules and blood flow through the prostate. This helps determine whether cancer is present and, if so, whether it is aggressive and if it has spread. Occasionally, MRI of the prostate is used to evaluate other prostate problems, including:
- infection (prostatitis) or prostate abscess
- an enlarged prostate, called benign prostatic hyperplasia (BPH)
- abnormal conditions present at birth
- complications after pelvic surgery
How is a Prostate MRI Performed?
MRI is typically done on an outpatient basis. During the MRI, the person who operates the machine will watch you from another room and you can use the intercom device (like a walkie-talkie) to talk to them. The test typically lasts 30 to 60 minutes, but may take longer. You may be asked to wear a hospital gown or clothing without metal fasteners. Certain types of metal can cause inaccurate images. You lie on your back on a narrow table. The table slides into the middle of the MRI machine. It is important to lay as still as possible for best quality images.
Small devices, called coils, may be placed around your hip area. These devices help send and receive the radio waves. They also improve the quality of the images. For prostate MRI, a small coil may be placed into your rectum. This coil must stay in place for about 30 minutes while the images are taken.
Some exams require a special dye, called contrast media. The dye is most often given before the test through a vein (IV) in your hand or forearm. The dye helps the radiologist see certain areas more clearly. When the contrast material is injected, it is normal to feel coolness and a flushing sensation for a minute or two. The intravenous needle may cause you some discomfort when it is inserted and once it is removed, you may experience some bruising. There is also a very small chance of irritation of your skin at the site of the IV tube insertion.
Most MRI exams are painless. However, some patients find it uncomfortable to remain still. Others may feel closed-in (claustrophobic) while in the MRI scanner. Sedation may be arranged if you have significant anxiety, but fewer than one in 20 require it. The scanner can be noisy and you may be offered or you may request earplugs to reduce the noise of the MRI scanner, which produces loud thumping and humming noises during imaging. MRI scanners are air-conditioned and well-lit. Some scanners have music to help you pass the time. It is normal for the area of your body being imaged to feel slightly warm, but if it bothers you, notify the radiologist or technologist.
How to Prepare for the Test
You may be asked not to eat or drink anything for 4 to 6 hours before the scan. Tell your health care provider if you are afraid of close spaces (have claustrophobia). You may be given a medicine to help you relax and be less anxious. Or, your provider may suggest an open MRI, in which the machine is not as close to the body.
Before the test, tell your provider if you have:
- Brain aneurysm clips
- Artificial heart valves
- Heart defibrillator or pacemaker
- Inner ear (cochlear) implants
- Kidney disease or dialysis (you may not be able to receive contrast)
- Recently placed artificial joints
- Vascular stents
- Pain pumps
- Worked with sheet metal in the past (you may need tests to check for metal pieces in your eyes)
- Many implanted devices will have a pamphlet explaining the MRI risks for that particular device. If you have the pamphlet, bring it to the attention of the scheduler before the exam. MRI cannot be performed without confirmation and documentation of the type of implant and MRI compatibility. You should also bring any pamphlet to your exam in case the radiologist or technologist has any questions.
Because the MRI contains strong magnets, metal objects are not allowed into the room with the MRI scanner:
- Pens, pocket knives, and eyeglasses may fly across the room.
- Items such as jewelry, watches, credit cards, and hearing aids can be damaged.
- Pins, hairpins, metal zippers, and similar metallic items can distort the images.
- Removable dental work should be taken out just before the scan.
Tell the technologist or radiologist about any shrapnel, bullets, or other metal that may be in your body. Foreign bodies near and especially lodged in the eyes are very important because they may move or heat up during the scan and cause blindness. Dyes used in tattoos may contain iron and could heat up during an MRI scan. This is rare. Tooth fillings, braces, eyeshadows and other cosmetics usually are not affected by the magnetic field. However, they may distort images of the facial area or brain.
Benefits of Prostate MRI
- MRI is a noninvasive imaging technique that does not involve exposure to radiation.
- MR images of the body’s soft-tissue structures are clearer and more detailed than those of other imaging methods. This detail makes MRI a valuable tool in early diagnosis and evaluation of the extent of tumors, such as prostate cancer.
- MRI has proven valuable in diagnosing a broad range of conditions, including cancer. It is also useful in diagnosing benign conditions such as an enlarged prostate and infection.
- Mp-MRI helps distinguish between low-risk/slow-growing and high-risk/aggressive prostate cancers. It also helps determine if cancer has spread beyond the prostate.
- MRI can detect abnormalities that might be obscured by bone with other imaging methods.
- The MRI gadolinium contrast material is less likely to cause an allergic reaction than the iodine-based contrast materials used for x-rays and CT scanning.
Risks of Prostate MRI
- The MRI exam poses almost no risk to the average patient when appropriate safety guidelines are followed.
- If sedation is used, there is a risk of using too much. However, your vital signs will be monitored to minimize this risk.
- The strong magnetic field is not harmful. However, it may cause implanted medical devices to malfunction or cause distortion of the images.
- Nephrogenic systemic fibrosis is a recognized, but rare, complication related to injection of gadolinium contrast. It usually occurs in patients with serious kidney disease. Your doctor will carefully assess your kidney function before considering a contrast injection.
- There is a very slight risk of an allergic reaction if contrast material is used. Such reactions are usually mild and controlled by medication. If you have an allergic reaction, a doctor will be available for immediate assistance.
Normal Results and Limitations of Prostate MRI
A normal result generally means your pelvic area appears normal but you need to be aware of the following limitations of an MRI:
High-quality images depend on your ability to remain perfectly still and follow breath-holding instructions while the images are being recorded as well as technical factors such as presence of implants and other metallic objects that can make it difficult to obtain clear images.
MRI cannot always distinguish between cancer and inflammation or the presence of blood products within the prostate. Blood may sometimes appear due to a prostate biopsy. To avoid confusing any bleeding with cancer, your doctor may wait six to eight weeks after prostate biopsy to perform prostate MRI. This will allow any remnants of bleeding to resolve.
MRI typically costs more and may take more time to perform than other imaging methods. Talk to your insurance provider if you have concerns about the cost of MRI.
What Abnormal Results May Mean
Abnormal results in a man may be due to:
- Bladder cancer
- Colorectal cancer
- Prostate cancer
- Testicular cancer
Abnormal results in both males and females may be due to:
- Avascular necrosis of the hip
- Birth defects of the hip joint
- Bone tumor
- Hip fracture
Alternatives to a Prostate MRI
- CT scan of the pelvic area
- Vaginal ultrasound (in women)
- X-ray of the pelvic area
A CT scan may be done in emergency cases, since it is faster and most often available in the emergency room.
MRI – pelvis; Pelvic MRI with prostate probe; Magnetic resonance imaging – pelvis
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