Prostate MRI is a test that provides detailed images of the prostate. The test is most commonly done to look for clinically significant cancer of the prostate. Reporting of prostate MRI uses PIRADS. This is a scale that conveys how suspicious an abnormality is from 1 to 5.
What is prostate MRI?
A prostate MRI is an imaging test that is focused on the prostate. The test is optimized to detect cancers of the prostate. We can also detect prostatic enlargement (BPH), inflammation, cysts, and other abnormalities of the prostate.
How to prepare for a prostate MRI?
Some facilities will require a four hour fast and an enema before the test. This is important because any rectal gas can degrade the images. The facility where you have the test will provide instructions.
Some facilities will have you wait up to 6 weeks after a prostate biopsy.
A mild sedative may be prescribed if you have claustrophobia.
You should tell the technologist about any implants, devices or other metal in your body. You should remove jewelry and other accessories.
What to expect during prostate MRI
The test is performed in a radiology department or outpatient imaging center by a specially trained technologist. You will have a IV placed in your arm since contrast is injected for the test.
The test can take up to an hour. You will be placed in a MRI machine which has a table and a large donut like opening. You will hear the MRI machine making noises as the images are obtained.
Indications for prostate MRI
Prostate MRI is often ordered when a man has an elevated PSA blood test. Elevated PSA blood test is non specific but can sometimes indicate that cancer is present.
MRI of the prostate is sometimes ordered when there is an abnormal rectal exam of the prostate done by a physician and an abnormality is suspected.
Prostate MRI is also used for surveillance of men who have prostate cancer.
Why is prostate MRI done?
Many prostate MRIs are ordered by urologists when they are concerned that a patient may have cancer because of an abnormal blood test or because they feel something on their exam of the prostate.
Prostate MRI helps find suspicious areas to biopsy. Prostate MRI helps focus a biopsy and provide a higher chance of finding cancer. Doing the biopsy by randomly sampling the prostate can miss a clinically significant cancer.
Prostate MRI is also reassuring when it is negative. Prostate MRI will not detect all clinically significant cancer so a biopsy may still be needed if the test is negative.
Prostate MRI technique
Prostate MRI is obtained using numerous sequences with multiple images focused on the prostate. The various sequences done provide information which help in detecting cancer and other abnormalities. We do imaging before and after contrast administration.
Are you sedated for prostate MRI?
Usually not. If you have claustrophobia then a light sedative may be administered prior to the test.
How long does prostate MRI take?
Usually 45 minutes to an hour.
Does prostate MRI hurt?
It is usually painless. Some patients may find it hard to be still during the test or be enclosed in the MRI machine.
Who interprets a prostate MRI?
Prostate MRI is interpreted by a trained radiologist who is a medical doctor specializing in medical imaging.
How are the results reported?
The radiologist will scrutinize the prostate looking for areas that may represent cancer. There is a grading system for abnormalities which may represent cancer called PIRADS.
Abnormalities in the prostate are graded based on suspicion for cancer from PIRADS 1 to 5. A lesion with PIRADS 5 is considered a highly suspicious lesion for cancer. The grading system is well established and makes interpretation more uniform across different radiologists and institutions.
What happens if an abnormality is found on the prostate MRI?
Suspicious lesions for cancer (PIRADS 4 and 5) are usually biopsied. Some specialists will watch a PIRADS 3 lesion rather than biopsy. PIRADS 1 and 2 lesions are usually left alone.
Does an abnormality on prostate MRI mean cancer?
Not always. We grade lesions of the prostate from 1 to 5 based on suspicion of cancer.
The radiologist will then mark the suspicious spot on the MRI images so that the urologist can reach it during the biopsy. The urologist may still do the random biopsies of the prostate but now has a specific target as well.
Not every abnormal area mentioned on the prostate MRI will turn out to be cancer. Inflammation and some other abnormalities of the prostate can look similar in some cases.
Where do most prostate cancers happen in the gland?
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 especially helpful in this region.
Can MRI tell us if the prostate cancer has spread?
The prostate MRI will also identify if the cancer has spread outside of the prostate gland. This indicates a worse prognosis.
It can also identify abnormal lymph nodes and bone lesions in the pelvis.
Additional imaging tests may be needed for the rest of the body if you get diagnosed with prostate cancer.
Can an MRI show prostate inflammation?
Yes, we call this prostatitis. Sometimes inflammation can look like cancer on imaging.
Prostate MRI: summary
Prostate MRI is a test that provides detailed images of the prostate and helps detect significant cancer. Prostate MRI is helpful because it allows a targeted biopsy of any suspicious lesions in the prostate. Prostate MRI can also identify any spread of the cancer in the pelvis.