What is PI-RADS and why should you care?

PI-RADS is an acronym and it stands for “prostate imaging — reporting and data system” but what it really is is a highly structured method for reporting what can be seen on certain types of prostate-specific magnetic resonance imaging (MRI) scan and how to interpret these data.

Understanding the PI-RADS system in detail is complicated, and we have no intention of trying to explain and interpret all of the details. Our goal is much simpler, which is to try to help patients understand why PI-RADS data are becoming important and what a basic PI-RADS grade might mean if you are given one in association with a prostate MRI — which you probably should be today. We will also provide links to some of the easily accessible PI-RADS data for those readers who like to get into the details.

So … The PI-RADS classification and reporting system is based on an earlier system (BIRADS) developed for reporting breast cancer imaging data. And the PI-RADS system was initially developed by the European Society of Urogenital Radiology (ESUR) in 2012.

It is becoming quite common for men to be given multiparametric MRI scans as one element in the work-up of a patient who is considered to be at risk for clinically significant prostate cancer, or as a repetitive element in the monitoring of patients who have been diagnosed with prostate cancer but who are being monitored on some form of active surveillance protocol.

These types of MRI scan are commonly obtained using techniques that can include a series of factors, such as sequential, high-resolution, T2- or T3-weighted morphological images; diffusion-weighted imaging (DWI), dynamic contrast-enhanced (DCE) images, and even proton magnetic resonance spectroscopy (1H-MRS) — but don’t worry too much about the details. What is important is that a standardized system has been developed to give a specific score (on a scale of 1 to 5) to each variable for each lesion that can be seen on the MRI scans. Rather like a Gleason grade, a score of 1 is considered to be most probably benign and a score of 5 is considered to be highly suspicious of a prostate malignancy.

And, as with Gleason scoring, there are two levels to the system. The first level is the one described above, in which a score is assigned to each image of each lesion. But the second level is one where these scores are added together to provide a total PI-RADS grade and classification for each lesion, as shown below:

PI-RADS scoring system

As you can see, each lesion for each patient can be classified as having a PI-RADS grade from I to V, and how that grade is assigned to a particular lesion depends on whether the patient did nor did not have an 1H-MRS PI-RADS score in addition to the standard T2 (or T3), DWI, and DCE PI-RADS score. If the patient does have an 1H-MRS PI-RADS score in addition to the other three standard scores, then his total PI-RADS score can run from 4 up to 20 for each visible lesion. If there is no 1H-MRS PI-RADS score, then his scores can only range from 3 to 15 for each visible lesion.

We are still relatively early in the process of understanding exactly how to interpret data from the PI-RADS scoring and classification process, but if you do have an MRI as one element in your diagnosis, work-up, or monitoring, you should be asking your doctor if he can tell you your PI-RADS scores for each lesion, because it does certainly give one more way to help to understand your risk, and it does this in a highly standardized manner.

Now, here are some other links that can help you to find out more about the PI-RADS system if you are interested:

One of the opportunities that is clearly presented by the PI-RADS system is that it may well be able to help us to not biopsy men who are at very low risk for clinically significant disease … but we do need more data before this becomes a clinically valid strategy, and we also need to understand that, here in America, the costs associated with MRI scanning are far higher than they are in most of the rest of the world.

8 Responses

  1. Thank you for explaining how vital the use of MRIs is to helping make informed decisions.

  2. Dear kEN:

    I am not so sure that I would necessarily characterize the use of MRIs as being “vital” under all circumstances. They can certainly be “useful” and “helpful” under appropriate circumstances, but that’s not quite the same thing. Sometimes they may just be an expensive waste of time and money.

  3. So I had a 3-T MRI before starting salvage radiation therapy to try to find where my biochemical recurrence after RP may have been located. Nothing was found but I started ADT and had IMRT. PSA is now zero. You think this new technology was used?

  4. Robert:

    It is utterly impossible for me to provide a meaningful answer to your question. You’d have to ask your doctors.

  5. Actually my term was not “all”.

    We discussed MRIs about 6 months ago. As to how important they are becoming, we can use two basic rules: who is investing time and money for investigation and who would go so far as to affect chance capable of revealing a difference path in treatment and diagnosis.

    The answer is Harvard for an extremely accurate focal laser ablation (FLA) needle placement. Not to mention their numerous MRI quality enhancements. Next we have UCLA, after 1,300 MRIs, MRI-guided biopsies, starting a short Phase 2 FLA trial on September 19, with the manufacturer’s involvement, and aimed at becoming a world class MRI, MRI-guided biopsy and MRI-guided FLA center. They feel they can teach NIH a few things. Next UCSF added their second 7-T mpMRI machine, along with the University of Minnesota, who finished a 7-T MRI trial for prostates, and the universities of Alabama and Iowa just installing 7 T. By the way, the University of Texas will soon publish all, not a few selected but all MRI FLA outcomes. The time of change is coming. And imaging is at the tip of the arrow.

  6. Dear kEN:

    No, You’re right. Your term wasn’t “all”. Your term was “vital”. As yet the degree of “vitalness” of mpMRI scanning is (at best) restricted to a subset of patients, and even when we have a lot more data, that is likely to continue to be true. What people with large enough research grants to acquire the right toys are researching and what becomes good and accepted clinical practice are two very different things.

  7. Sitemaster:

    Thank you for this very useful reference article!


    What’s with this 7-T stuff, which I take to mean tesla; is that right? My impression was that 3-T was slowly emerging toward center-of-excellence status, and suddenly there appears to be a huge leap to 7-T, which I’d never heard of in a clinical application. (Hadn’t heard of 4-T, 5-T or 6-T either.) I’d heard that an old rule of thumb was that it took about $1 million for each tesla level. Any insight on that for 7-T? Do you have to avoid iron rich food before 7-T imaging? (Just kidding. I think.)

  8. I have ADC 242 x 10 -6 mm2, PI-RADS 5 lesion measures 1.9 x 1.7 x 1.4 cm.

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