How Does a Prostate MRI Work?

Prostate cancer is a common cause of cancer. 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, such as with prostate MRIs. These allow healthcare providers to create individualized treatment plans. As prostate MRIs become more widely available, healthcare providers are now using them to: 

• Map where to get samples from the prostate during a prostate biopsy

• Follow people who are being monitored closely (active surveillance)

• Determine when prostate cancer has spread beyond the prostate

Let’s take a closer look at how MRI technology can be used to diagnose and treat prostate cancer — and how this technology can be used in the future. 

How do prostate MRIs work?

Prostate MRIs work just like other types of MRIs. Magnetic resonance imaging (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 will 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. Plus, unlike CT scans and X-rays, MRIs are radiation free. 

Is a prostate MRI better than a biopsy for diagnosing cancer?

Not exactly. Prostate MRIs don’t replace prostate biopsies for prostate cancer diagnosis. But when used with prostate biopsies, prostate MRIs can improve the accuracy of a diagnosis.

Prostate biopsies use ultrasound to help the urologist decide where to put the needle to obtain a tissue sample. It’s possible to “miss” a tumor using this method. By getting an MRI first, your urologist will have an exact map of where to get a sample. This will make sure that the right tissue is sent for evaluation, so you get an accurate diagnosis of your prostate cancer. 

How do you prepare for a prostate MRI?

There’s not much you need to do to prepare for your MRI. If you’re getting sedation medication, you won’t be able to eat or drink anything for about 8 hours before your MRI. If your provider needs to use an endorectal coil during your MRI, they might ask you to take an enema a few hours before the procedure. Otherwise, you don’t need to do anything to prepare. 

What can you expect from the procedure?

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

• 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 bed. If you need contrast for your study, you’ll get an intravenous (IV) line placed, and the technician 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 ear plugs: You’ll be given a pair of ear plugs to wear during the MRI, since the machine makes loud noises. 

• Lie still: During the study, the MRI bed will be slowly moved into the MRI machine. 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 a few hours for the radiologist to finish your MRI report. Your healthcare team will call you to go over the results. 

How long does a prostate MRI take?

A prostate MRI takes about 30 minutes. This is how long you will spend lying on the MRI bed. It doesn’t include the time it takes to complete your safety check or have additional procedures like an IV line or endorectal coil placements. It’s a good idea to block 2 hours for the entire appointment. 

What are the risks and benefits of getting a prostate MRI?

MRI doesn’t use radiation, and it isn’t invasive or painful. In fact, it’s one of the safest medical procedures available. So, there’s not a lot of risk that comes with getting an MRI, but there are a lot of benefits. This makes the prostate MRI a powerful tool. 

Benefits of having a prostate MRI

There are several benefits to having a prostate MRI, including:

• Improved staging and faster treatment: Prostate MRIs can show whether the cancer is only in the prostate or has spread to nearby areas. This is important for staging and helps with deciding on what kind of surgery and treatment you might need. Since this information will be available even before your prostate biopsy, you may start treatment faster.

• Helpful indicator for possible active surveillance: Some people don’t need treatment for prostate cancer right away. But they’ll need to be watched closely by their healthcare providers in the coming period. This is called “active surveillance.” A prostate MRI will help the healthcare team get a good biopsy so they can determine if you’re a candidate for active surveillance. 

There are many ongoing studies to see how else prostate MRIs can be used to help treat prostate cancer. In the future:

• Some people might be able to avoid unnecessary prostate biopsies if their prostate MRIs are normal.

• Prostate MRIs may also be used to find cancer earlier in people who are at higher risk for developing prostate cancer. This can be lifesaving, since prostate cancer is more treatable when it’s found early. 

• Prostate MRIs can help guide focal therapy, which could mean fewer side effects.

Risks of 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 distraction 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. There’s always a healthcare professional on site to help in case you have an allergic reaction to the contrast. 

• Cost: Even though prostate MRIs have huge benefits, insurance companies don’t always cover them. Your treatment team can write a “letter of necessity,” which often is enough to have your MRI covered. Prostate MRIs can cost anywhere between $400 and $2,500. It may be higher, though, depending on your insurance and where you live. You can use funds from a health savings account (HSA) or flexible spending account (FSA) to help offset the cost. 

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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, Michigan in the emerging field of theranostics. His primary clinical focus is on the treatment of people with metastatic prostate and neuroendocrine cancers.

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