PI-RADS standards produce 'disheartening' results, fail to fix mpMRI quality issues

Minimum technical standards outlined in the prostate imaging reporting and data system version 2 have not improved the image quality problems plaguing multiparametric prostate MRI exams, researchers reported Wednesday.

That finding comes after radiologists assessed prostate images from 62 different institutions performed over a one-year period, and published their results March 4 in Academic Radiology. Although a majority of scans were considered “adequate,” few were deemed “high quality.” It’s a disappointing discovery given the dire need to remedy the center-to-center variability in mpMRI exam quality, the authors noted.

“This study shows a disheartening rate of inadequate exams among mpMRI studies of the prostate,” corresponding author Baris Turkbey, MD, with the National Cancer Institute, and colleagues noted. “Looking forward, it is apparent the general quality of prostate mpMRI should be improved to deliver better diagnosis in prostate cancer care,” they wrote later.  

Distinguishing clinically relevant prostate cancer from the benign variety is a critical challenge in the field. But PI-RADS version 2 was designed to alleviate this issue by standardizing imaging sequences and limiting scan quality variability. Turkbey et al. also pointed out that some studies have found wide-ranging adherence to these technical guidelines across institutions; some departments report as low as a 17% compliance rate.

To investigate this phenomenon further, the group asked six radiologists to asses 62 prostate MRI exams (including T2-weighted and diffusion-weighted) referred to a single center. Each scan was assigned a quality ranking on a 1-5 scale. Out of those images, 52 T2 and 38 DWI scans were graded as “adequate” by a majority of readers.

According to their research, adherence to the PI-RADS minimum standards did not play a role in improving image quality.

“Many centers found a way to produce diagnostic images while essentially overlooking the PI-RADS version 2 standards, while many who demonstrated strict adherence to the standards had poor results,” the authors added.

And even if an image was produced following the standards, radiologists were no more likely to perceive it as a higher-quality image. That was especially true for diffusion-weighted scans.

PI-RADS has undoubtedly improved the sensitivity of MRI-guided biopsies and has allowed physicians to avoid the invasive procedure in those unlikely to have prostate cancer. The problem in image quality, however, remains an issue that must be addressed, the researchers wrote.

“There is an urgent need for new quality assurance tools, involvement of MRI manufacturers, the MR physics community and individual efforts on the part of radiologists to improve mpMRI,” the authors wrote.

Turkbey and colleagues argued that a standard based on “objective imaging characteristics” may be required to replace the current criteria. They did not go as far as to make formal recommendations, but pointed to image noise, distortion and susceptibility artifacts as potential target areas.