Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) - Prostate

• What is MRI of the Prostate?
• What are some common uses of Prostate MRI?
• How should I prepare for the MRI?
• How is the MRI performed?
• What will I experience during the MRI?
• Who interprets the results and how do I get them?
• What are the limitations of MRI of the Prostate?
• What are the benefits vs. risks?

What is MRI of the Prostate?

Magnetic resonance imaging (MRI) is a noninvasive way of viewing organs, soft tissues, bone and other internal body structures without the use of x-rays. MRI uses a magnetic field and radio waves together with a computer to create cross-sectional pictures of various parts of the body. Detailed MR images allow physicians to better evaluate parts of the body that may not be visible with other imaging methods such as x-ray, ultrasound or computed tomography (CT scan). MRI has proven valuable in diagnosing a broad range of conditions, including cancer, heart and vascular disease, stroke, and joint and musculoskeletal disorders. The prostate is a walnut-size gland that is part of the male reproductive system. It is located below the bladder, where urine is stored, and surrounds the urethra, the tube that carries urine and other fluids out of the body. The prostate helps make the milky fluid called semen that carries sperm out of the body when a man ejaculates. Ultrasound and MRI are the most commonly used techniques to image the prostate gland.

What are some common uses of Prostate MRI?

The three most common prostate problems are:

• Infection (prostatitis)

• Enlarged prostate, called benign prostatic hyperplasia (BPH)

• Prostate cancer

The prostate tends to grow bigger with age due to the development of BPH. A tumor or infection can also enlarge the prostate. All of these conditions may squeeze the urethra, causing urinary problems.

Diagnosing a prostate problem may require a series of tests including an MRI exam, which can help identify abnormalities. If a biopsy has confirmed cancer, a doctor may use MRI or other imaging techniques to determine if the cancer is confined to the prostate, or if it has spread outside the capsule of the prostate gland and elsewhere in the body.

How should I prepare for the MRI?

Your MRI exam may involve the use of an endorectal coil, a thin wire covered with a balloon, placed inside the rectum. This coil helps focus on the prostate and surrounding structures. To prepare for an MRI with the endorectal coil, you should eat light meals on the day prior to and on the day of your exam. This will help make it easier to insert the coil. You may also be asked to use an enema preparation prior to your exam. An enema involves injecting liquid into your large intestine through your rectum to help clear the bowel. Prior to your exam, you may continue to take your usual medications, unless you are told otherwise. You may be given a hospital gown to wear during the exam. Please see general description of MRI procedures for additional information on patient preparation.

How is the MRI performed?

You will lie on your back on a table that can be moved into and out of the MRI. Cushions are used to maintain the proper position of your body and to make you as comfortable as possible. The technologist will leave the room while the MRI examination is performed. The patient is able to communicate with the technologist at any time using an intercom. A friend or relative may stay in the room. If an endorectal coil is to be used in your MRI exam, a physician will insert the wire coil, which is enclosed within a small, flexible plastic tube, into your rectum. Once inserted, a balloon is inflated to hold the coil in place during the exam. When your exam in complete, the balloon is deflated and the coil is removed. Depending on how many images are needed, the exam will generally take 30 to 45 minutes, although a very detailed study may take longer. During imaging, you will be instructed not to move. You will know when images are being recorded because you will hear tapping or thumping sounds when the coils that create the magnetic field are turned on. In between sequences, you will be able to relax. Patients are generally required to remain still for only a few minutes at a time. Some patients will require an injection of a contrast material to enhance the visibility of certain tissues or blood vessels. The contrast material is injected about two-thirds of the way through the exam. A small IV is placed in an arm or hand vein for the injection.

When your exam is completed, you may wait a short time on the table while the images are examined to ensure no additional images are needed.

What will I experience during the MRI?

MRI of the prostate is a pain-free procedure. During the exam, your prostate may feel slightly warm, but this is normal and harmless. If an endorectal coil is used, you will feel pressure in your rectum similar to that experienced during a digital rectal exam. It is important to remain perfectly still when images are being recorded. MRI scanners are air-conditioned and well-lit. During your exam, you will be able to talk to the technologist, who will observe you from an adjacent room throughout the exam. You may request earplugs to reduce the thumping and humming noises of the MRI scanner. W can provide you with stereo headsets.

Who interprets the results and how do I get them?

A neuroradiologist, who is a physician experienced in head, neck and spine MRI examinations, will analyze the images and send a signed report with his or her interpretation to the patient's personal physician. A preliminary interpretation may be available shortly after the exam and a formal report of the complete results will be sent to the referring physician within a day. Your primary physician or the radiologist may discuss the findings of the MRI examination with you. New technology also allows for distribution of diagnostic reports and referral images over the Internet to our facility.

What are the limitations of MRI of the Prostate?

Patients who are claustrophobic may have to be sedated during an MRI exam or examined in one of the newer open MRI units. A person who is very obese may not fit into the opening of a conventional MRI machine. The presence of an implant or other metallic object often makes it difficult to obtain clear images, and patient movement can have the same effect. A patient with severe pain may not be able to lie still during imaging. MRI may not always distinguish between tumor tissue and edema fluid. It cannot detect calcium present in a tumor. The MRI findings by themselves do not establish an absolute diagnosis, but in most situations the findings will suggest the correct diagnosis. The images must be interpreted along with the patient's history, physical findings, and information from other tests. MRI may be more costly than other imaging methods including CT scanning.

What are the benefits vs. risks?

Benefits:

• MRI is a totally noninvasive imaging technique that does not require exposure to ionizing radiation.

• MRI provides more clear and detailed images of the soft-tissue structures of the body than other imaging methods. The endorectal coil provides highly detailed images of prostate anatomy and pathology, not possible with other imaging modalities. The detail makes MRI an invaluable tool in early diagnosis and evaluation of tumors.

• The contrast material sometimes used for MRI does not contain iodine, and therefore is far less likely to produce an allergic reaction than the contrast materials used for conventional x-rays and CT scanning.

Risks:

• There are no definite side effects from any type of MRI study, including MR angiography.

• An undetected metal implant may be affected by the magnetic field. The procedure should be avoided in any patient with a pacemaker, implanted neurostimulator, certain types of metallic ear implants (cochlear implants) or metallic object within the eye socket. It should also be avoided if the patient has a port for delivering insulin or chemotherapy (however, many ports are detachable so patients can safely undergo MRI examinations).

• If sedation is used, there are risks of excessive sedation. The technologist monitors the patient's vital signs to minimize this risk.

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