Prostate MRI is a frequently ordered test to take a closer look at the prostate gland. The test is performed in a radiology department or outpatient imaging center by a specially trained technologist. The test takes about 30-45 minutes and does not require any special preparation. The MRI machine is noisy and you will be required to lay still.
Prostate MRI is often ordered when a man has an elevated PSA blood test or an abnormal rectal exam of the prostate. PSA can be elevated in cancer in addition to other conditions such as prostatitis (inflamed prostate). Since cancer is the most common cancer in men, the test will help identify suspicious areas. If your doctor feels a lump along the prostate on rectal exam, then this test may be ordered.
Prostate MRI is interpreted by a trained radiologist. The test often has hundreds of images to look at and can take some time to interpret. The radiologist will scrutinize the images looking for areas that may represent cancer. There is a grading system based on suspicion from 1 to 5, with 5 being a highly suspicious lesion for cancer. The grading system is well established and makes interpretation more uniform.
Many prostate MRIs are ordered by urologists who plan on performing a biopsy of the prostate. This is often done with multiple areas being sampled and then examined by a pathologist for signs of cancer. The problem is that those areas randomly sampled by the urologist can miss significant cancer or more aggressive cancer.
The prostate MRI is good at detecting clinically significant cancer. That is the type of cancer that treatment is needed for. The radiologist will use specific criteria to determine whether an abnormal spot is suspicious or not. The radiologist will then mark the spot so that the urologist can reach it during the biopsy. The urologist may still do the random biopsies but now has a more specific and suspicious target as well. Not every abnormal area mentioned on the prostate MRI will turn out to be cancer. Inflammation of the prostate can look similar in some cases.
The prostate gland is divided into zones, and most (about 70%) cancers occur along the surface or peripheral zone. The rest occur in the more central gland. These are tougher for the urologist to diagnose when randomly doing biopsies. The MRI will be helpful in this region.
The prostate MRI will also identify if the cancer has spread outside of the prostate capsule. This indicates a worse prognosis. It can also identify abnormal lymph nodes and bone lesions in the pelvis. Your clinical doctors will use this information to guide treatment.