How Does a Prostate MRI Work?

Prostate cancer is one of the most common cancers in men. Not all types of prostate cancer are the same, though. And not all types need immediate treatment. 

What’s more, treatment options for prostate cancer are changing. Prostate MRIs are an important part of care. They allow healthcare professionals to create individualized treatment plans. 

Let’s take a closer look at how magnetic resonance imaging (MRI) technology helps in diagnosing and treating prostate cancer — and how this technology can be used in the future. 

Why might I need a prostate MRI?

You may need a prostate MRI if:

• You need a prostate biopsy: Prostate MRIs map specific areas where your healthcare team should get samples from the prostate during a prostate biopsy.

• You’re undergoing active surveillance: Prostate MRIs may be a routine part of your care plan if your treatment includes active surveillance for low-risk prostate cancer.

• Your prostate cancer changed: Prostate MRIs can be used to determine if your prostate cancer is behaving differently. 

What are the benefits of a prostate MRI?

There are several benefits of a prostate MRI, including biopsy accuracy and avoiding repeat biopsies. Let’s look at these and more benefits below.

Are there any risks to getting a prostate MRI?

MRIs are safe, and they’re free of radiation and pain. But there are some possible risks and downsides, including:

• Claustrophobia: If you have claustrophobia or don’t like being in small, enclosed spaces, getting an MRI may make you nervous. MRI technologists can talk to you and play music or videos to help distract you. If these techniques aren’t enough, you can have sedation medication to help you get through the MRI.

• Allergic reactions: You might need a contrast injection for your MRI. Contrast helps the radiologist see the prostate and other organs more clearly. Some people are allergic to the dye and can have an allergic reaction. But contrast allergies are very rare. There’s always a healthcare professional on site to help in case you have an allergic reaction to the contrast. 

• Cost: Depending on your deductible, the MRI may still carry a significant cost. You can use funds from a health savings account (HSA) or flexible spending account (FSA) to help offset the cost. 

How do prostate MRIs work?

Prostate MRIs work just like other types of MRIs. MRI is a radiology study that uses magnetic fields to create images. It’s one of the most detailed imaging techniques available today. MRIs can produce 2D (flat images) or 3D images. 

During an MRI, you lie down on a table that’s surrounded by a large tube. This tube contains the MRI magnet. The magnet creates a magnetic field. The protons inside atoms in your body line up in response to the magnetic pull. This allows software to create images of structures inside the body. MRIs are especially useful when trying to look at organs, muscles, and blood vessels. 

How do you prepare for a prostate MRI?

There’s not much you need to do to prepare for your MRI. Here are some things you may be asked to do:

• Diet changes: You don’t need to change what you eat before a prostate MRI. But if you’re getting sedation medication, you won’t be able to eat or drink anything for about 8 hours before your MRI. 

• Medication changes: You don’t need to stop your medications before your prostate MRI. If you’re receiving sedation medication before your prostate MRI, your healthcare team may ask you to skip your morning medications or take them after your MRI.

• Enema preparation: Your healthcare team may ask you to give yourself an enema before your prostate MRI. This is if you need to use an endorectal coil during your MRI.

• Contrast preparation: Your healthcare team may ask you to complete a questionnaire or answer questions if you need contrast for your prostate MRI. This will go over topics like your allergies, medications, and whether you’ve received contrast in the past. They may also ask you to get blood work to check your kidney health. 

What can you expect from the procedure?

Here’s what you can expect during your prostate MRI:

• Go through a safety check: You’ll go through a safety checklist with the MRI technologist. The technologist will make sure you don’t have any metal in your body from medical devices that aren’t MRI safe. You’ll remove jewelry, watches, or other items that contain metal. You’ll also be asked to change into a gown to make sure there’s no metal in your clothes. 

• Get in position: Next, you’ll go into the MRI room and lie on the MRI table. If you need contrast for your study, you’ll get an intravenous (IV) line placed, and the technologist will give the contrast through your vein. If your MRI requires an endorectal coil, it will be inserted into your rectum. Since MRI technology has improved, endorectal coils aren’t used that often anymore. 

• Put in your earplugs: You’ll be given a pair of earplugs to wear during the MRI, since the machine makes loud noises. 

• Lie still: During the study, the MRI table will be slowly moved into the MRI tube. It’s important to lie as still as possible during the MRI so that the pictures are good quality. You may need to hold your breath for 10 to 20 seconds every once in a while. This is so the movement of your breathing doesn’t interfere with the images. 

• Head home: After the MRI, you can go about your normal daily activities. It will take  hours to days for the radiologist to finish your MRI report. Your healthcare team will follow up with you to go over the results. 

What happens after the MRI?

A radiologist will look at the images from your MRI and create a report with the findings. Your prostate MRI report will include:

• Measurements of your prostate

• The location and size of any tumors

• PI-RADS score 

• Any other important findings

Your report will also contain information about whether there’s any sign of cancer in nearby tissue, lymph nodes, and bone.  

You and your healthcare team will receive these results and create a care plan based on this information. 

What is a PI-RADS score?

A PI-RADS score is a number between 1 and 5. This score describes whether findings on a prostate MRI are likely to represent clinically significant cancer. 

“Clinically significant cancer” is a prostate cancer that’s likely to grow, spread, or cause harm if it isn’t treated. 

Here’s what PI-RADS scores mean:

• PI-RADS 1: Your prostate MRI looks normal. The chance of significant cancer is very low.

• PI-RADs 2: Your prostate MRI shows minor changes. But these changes don’t look like cancer and may be due to other causes like inflammation or enlargement. The chance of clinically significant cancer is low. 

• PI-RADS 3: Your prostate MRI shows changes, but it’s not clear if these changes are cancer. There’s a moderate chance that these changes are due to clinically significant cancer.

• PI-RADS 4: Your prostate MRI shows changes that are suspicious for clinically significant cancer. There’s a high chance that these changes are due to clinically significant cancer. 

• PI-RADS 5: Your prostate MRI shows changes that have classic signs of aggressive prostate cancer. There’s a very high chance these changes are due to clinically significant cancer.

Keep in mind that your PI-RADS score is only one piece of information. Your healthcare team will also use other pieces of information to determine whether you have clinically significant cancer, including biopsy results, PSA levels and trends over time, and your medical history. 

Frequently asked questions

Why trust our experts?

Written by:

Ronald W. Dworkin, MD, PhD

Ronald W. Dworkin, MD, is a board-certified anesthesiologist who has been practicing anesthesiology in a community hospital for 30 years. He has taught in the honors program at George Washington University for over 10 years and works as a senior fellow at the Hudson Institute.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

Reviewed by:

Brandon R. Mancini, MD, MBA, FACRO

Brandon R. Mancini, MD, MBA, FACRO, serves as medical director at BAMF Health in Grand Rapids, MI, in the emerging field of theranostics. His clinical focus is treating people with metastatic prostate and neuroendocrine cancers.

Our editorial standards

Meet our experts