What is a prostate gland?

The prostate gland is a walnut-sized gland located between the penis and the bladder that produces a special fluid that surrounds and protects sperm during ejaculation. Each year in the U.S., about 161,000 new cases of prostate cancer are diagnosed, according to data from the American Cancer Society, and nearly 27,000 deaths occur as a result of prostate cancer.

Magnetic resonance imaging plays an important role in diagnosing prostate cancer in its early stages, helping men receive the treatment they need to prevent the disease from spreading. In patients who have prostate cancer, a prostate MRI can also be used to determine if the cancer has spread beyond the prostate gland and to guide cancer treatments. Prostate MRI is also very useful in diagnosing prostate infections, congenital defects and benign prostate hyperplasia (BPH), a common, noncancerous cause of prostate enlargement.

How does a prostate MRI “work”?

Our bodies are composed primarily of water, and each water molecule contains hydrogen and oxygen atoms. These atoms contain tiny particles called protons which respond to magnetic fields, changing their positions or orientations to correspond with the magnetic charge. During an MRI, the machine’s magnets create a magnetic field that’s switched on and off, causing the protons to align in specific patterns. The MRI’s computer captures those patterns, creating highly-detailed cross-sectional images that can be viewed and interpreted by the doctor. Unlike X-rays and CT scans, magnetic resonance imaging doesn’t use ionizing radiation.

What happens during a prostate MRI?

Prior to your prostate exam, you’ll need to change into a gown and remove any jewelry or other metal. Then you’ll lie on your back on an exam table which is designed to slide inside the MRI machine, which is shaped like a large tube. Supports or pads may be used to help hold you in position while the scan is being performed. A contrast dye may be injected into your arm through an IV which will remain in place throughout the scan. The dye will help the radiologist and your doctor see the prostate gland and other tissues more clearly. When a contrast agent is used, a series of scans usually is performed first without any dye, then a second series is completed once the dye is injected.

When the exam begins, the exam table will slide into the machine. The table is controlled by a computer to ensure very precise movements that work in tandem with the imaging system. Throughout the exam, the technician performing the MRI will be outside the room, controlling the scan via a computer. However, you’ll be able to communicate with the technologist through an intercom system that’s built into the MRI or through headphones, which can also be used to pipe in music to drown out the noise of the machine.

Most exams take 45 minutes or less. Although you may find it a little uncomfortable to remain in one position for the time required by the scan, the scan itself is painless and noninvasive, and unlike X-rays and CT scans, it does not use ionizing radiation. Some patients find the experience of being enclosed within the device a little claustrophobic. If you find yourself feeling very anxious about the exam, you may be given a sedative beforehand to help you relax. In most cases, sedation is unnecessary. 

What is an endorectal prostate MRI?

An endorectal prostate exam uses a small coil that’s inserted into the rectum. The coil provides more detailed images required for some prostate evaluations. Before insertion, the coil is encased in a protective cover and lubricant is applied to make insertion easier and more comfortable. Once the coil is inside the rectum, a small inflatable balloon will help keep it in place. Most patients say the balloon exerts about the same amount of pressure as a digital rectal exam (DRE) performed to check for prostate enlargement. The coil and balloon will be removed as soon as the exam is over.

How will I feel after my MRI?

MRIs are noninvasive, and unless you’ve had sedation, you’ll be able to resume your regular activities immediately afterward. If you were administered a sedative, you’ll need someone to drive you home. A very few patients may have some mild stomach upset from the contrast dye, and in rare instances, allergic reactions with itching, hives or other symptoms may develop. If you notice any allergic symptoms, call the office or your own doctor right away.