E1902. An Interdisciplinary Approach to MRI Interpretation of Prostate Cancer (PIRADS vs 2.1): A Case-Based Review
  1. Nazanin Asvadi; Saint Vincent Hospital
  2. Steven Raman; University of California, Los Angeles
  3. Sohrab Afshari; University of California, Los Angeles
  4. Kuldip Mann; Saint Vincent Hospital
  5. Brian Midkiff; Saint Vincent Hospital
Multiparametric MRI (mpMRI) has a central role in detecting clinically significant prostate cancer (PCa) lesions and identifying the appropriate biopsy target. PI-RADS (Prostate Imaging-Reporting and Data System) supports a standardized high quality image acquisition, interpretation and reporting system. PI-RADS version 2.1 was published in March 2019 with modifications compared to the previous version, PI-RADS version 2.

Educational Goals / Teaching Points
Our educational goals are to provide a comprehensive review of the MR interpretation of PCa lesions using PI-RADS v 2.1, and delineate the PI-RADS v 2.1 scoring system updates compared to the previous PI-RADS v 2.0 and (3) review the PI-RADS limitations and potential pitfalls.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
mpMRI includes T2 weighted imaging (T2WI), diffusion weighted imaging (DWI) and dynamic contrast enhanced (DCE) sequences. PI-RADS v 2.1 addresses limitations and inconsistencies from v 2, including updates and clarifications to the assessment categories and technical parameters. Interpretation of PCa lesions using the PI-RADS scoring system is based on zonal anatomy. DWI and T2WI represent the key sequences for peripheral zone (PZ) and transitional zone (TZ) PCa lesions, respectively. Updates are made to incorporate the use of DWI in detection of TZ PCa lesions which have been shown to improve interreader agreement. Studies have also shown benefits of DCE MRI use in PCa detection. DCE may help with increase in sensitivity of the detection of TZ and PZ lesions, especially in men with low PSA level (<10 ng/ml), when technical issues are present with T2W or DWI, or for inexperienced readers. Biparametric MRI may be considered in certain cases. There are some limitations to the PI-RADS scoring system. For example, PI-RADS 2.1 discusses the normal appearance of central zone (CZ) and anterior fibromuscular stoma (AFMS) on mpMRI. However, there is no specific PI-RADS scoring for CZ and AFMS PCa.

Updates are made in PI-RADS 2.1 to address inconsistencies and limitations from PI-RADS 2, as well as add clarification for easier assessment of PCa lesions and reduce interreader variability in interpretation. Studies have shown mixed results regarding the improvement in diagnostic performance of the PI-RADS 2.1. Future studies are needed for continued assessment of PI-RADS v 2.1 accuracy and cancer detection rate with pathologic correlation and clinical follow-up.