Reviewed By Benjamin Taragin M.D. Department of Radiology, Montefiore Medical Center Bronx, N.Y. Revi…ew provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.more »
Definition
A magnetic resonance imaging (MRI) scan of the pelvis is a noninvasive method to create detailed pictures of the area between the hip bones. This part of the body is called the pelvic area.
The pelvic area contains the reproductive organs.
In women, it includes the womb (uterus), cervix, ovaries, and fallopian tubes.
In men, it includes the prostate gland and testicles.
Unlike x-rays and computed tomographic (CT) scans, which use radiation, MRI uses powerful magnets and radio waves. The MRI scanner contains the magnet. The magnetic field produced by an MRI is about 10 thousand times greater than the earth's.
The magnetic field forces hydrogen atoms in the body to line up in a certain way (similar to how the needle on a compass moves when you hold it near a magnet). When radio waves are sent toward the lined-up hydrogen atoms, they bounce back, and a computer records the signal. Different types of tissues send back different signals.
Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces dozens or sometimes hundreds of images.
Alternative Names
MRI - pelvis; MRI - hips; Pelvic MRI with prostate probe; Magnetic resonance imaging - pelvis
How the test is performed
You may be asked to wear a hospital gown or clothing without metal fasteners (such as sweatpants and a t-shirt). Certain types of metal can cause inaccurate images.
You will lie on your back on a narrow table, which slides into the middle of the MRI machine.
Small devices, called coils, may be placed around the hip area. These devices help send and receive the radio waves, and improve the quality of the images. If pictures of the prostate and recturm are needed, a small coil will 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 (contrast). The dye is usually given before the test through a vein (IV) in your hand or forearm. The dye helps the radiologist see certain areas more clearly.
During the MRI, the person who operates the machine will watch you from another room. Several sets of images are usually needed, each taking 2 - 15 minutes. Depending on the type of equipment, the exam may take 1 hour or longer.
How to prepare for the test
You may be asked not to eat or drink anything for 4 - 6 hours before the scan.
If you are having a pelvic MRI with a prostate probe, you must completely empty your bowels before the exam. This may be done using an enema or laxatives combined with a clear liquid diet. Your health care provider will give you specific instructions. Thorough cleansing of the large intestine is necessary for accurate pictures.
Before the test, tell the radiologist if you are currently receiving dialysis, as this may affect whether you can have IV contrast.
If you fear confined spaces (have claustrophobia), tell your doctor before the exam. You may be given a medicine to help you feel sleepy and less anxious, or your doctor may recommend an "open" MRI, in which the machine is not as close to the body.
The strong magnetic fields created during an MRI can interfere with certain implants, particularly pacemakers. Persons with cardiac pacemakers cannot have an MRI and should not enter an MRI area.
You may not be able to have an MRI if you have any of the following metallic objects in your body:
Tell your health care provider if you have one of these devices when scheduling the test, so the exact type of metal can be determined.
Before an MRI, sheet metal workers or any person that may have been exposed to small metal fragments should receive a skull x-ray to check for metal in the eyes.
Because the MRI contains a magnet, metal-containing objects such as pens, pocketknives, and eyeglasses may fly across the room. This can be dangerous, so they are not allowed into the scanner area.
Other metallic objects are also not allowed into 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.
How the test will feel
An MRI exam causes no pain. Some people may become anxious inside the scanner. If you have difficulty lying still or are very anxious, you may be given a mild sedative. Excessive movement can blur MRI images and cause errors.
The table may be hard or cold, but you can request a blanket or pillow. The machine produces loud thumping and humming noises when turned on. You can wear ear plugs to help reduce the noise.
An intercom in the room allows you to speak to the person operating the scanner at any time. Some MRIs have televisions and special headphones that you can use to help the time pass.
There is no recovery time, unless you need sedation. After an MRI scan, you can resume your normal diet, activity, and medications.
Why the test is performed
This test may be done if a female has any of the following signs or symptoms:
Abnormal vaginal bleeding
A mass in the pelvis (felt during a pelvic exam or seenon another imaging test)
A pelvic MRI is also frequently done to see if certain cancers have spread to other areas of the body. This is called staging. Staging helps guide future treatment and follow-up and gives you some idea of what to expect in the future. A pelvic MRI may be used to help stage cervical, uterine, bladder, rectal, prostate and testicular cancers.
Normal Values
A normal value means the areas being examined appear normal in size, shape, and structure.
What abnormal results mean
Results depend the nature of the problem. Different types of tissues send back different MRI signals. For example, healthy tissue sends back a slightly different signal than cancerous tissue.
Consult your health care provider with any questions and concerns.
What the risks are
MRI contains no ionizing radiation. To date, there have been no documented significant side effects of the magnetic fields and radio waves used on the human body.
The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions to the substance rarely occur. The person operating the machine will monitor your heart rate and breathing.
MRI is usually not recommended for acute trauma situations, because traction and life-support equipment cannot safely enter the scanner area and the exam can take quite a bit of time.
People have been harmed in MRI machines when they did not remove metal objects from their clothes or when metal objects were left in the room by others.
Special considerations
Tests that may be done instead of a pelvic MRI include:
A CT scan may be done in emergency cases, since it is faster and usually available right in the emergency room.
References
Wilkinson ID, Paley MNJ. Magnetic resonance imaging: basic principles. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. New York, NY: Churchill Livingstone; 2008:chap 5.
Gjelsteen AC. CT, MRI, PET, PET/CT, and ultrasound in the evaluation of obstetric and gynecologic patients. Surg Clin North Am. April 2008; 88(2): 361-90, vii.
Bohm-Velez M, Fleischer AC, Andreotti RF, Fishman EK, Horrow MM, Hricak H, Thurmond A, Zelop C, Expert Panel on Women's Imaging. Suspected adnexal masses. [online publication]. Reston (VA): American College of Radiology (ACR); 2005. 10 p.
Hricak H, Akin O, Sala E, Fleischer AC, Bohm-Velez M, Fishman EK, Mendelson E, Thurmond A, Goldstein S, Expert Panel on Women's Imaging. Endometrial cancer of the uterus. [online publication]. Reston (VA): American College of Radiology (ACR); 2005. 6 p.
Hricak H, Akin O, Sala E, Fleischer AC, Bohm-Velez M, Fishman EK, Mendelson E, Thurmond A, Goldstein S, Expert Panel on Women's Imaging. Invasive cancer of the cervix. [online publication]. Reston (VA): American College of Radiology (ACR); 2005. 6 p.
