Integrated Approach to PSMA PET with Multiparametric MRI of the Prostate

In this video case series, Dr. Louis Mazzarelli, Director of Molecular Imaging at Lawrence Memorial and Westerly Hospitals, explores the integrated use of PSMA PET and prostate MRI to improve lesion detection, characterization, and management planning in prostate cancer. This session focuses on how combining molecular and anatomic imaging provides complementary insights into both local and systemic disease.

Dr. Mazzarelli reviews a structured, practical approach to interpreting prostate MRI—emphasizing T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast enhancement—and demonstrates how these findings should be correlated with PSMA PET uptake for concordance or discordance. Through multiple cases, he illustrates how lesion conspicuity may vary between MRI and PSMA PET, highlighting the importance of integrating both modalities rather than relying on either alone.

A central theme of the presentation is intra- and intertumoral heterogeneity. Dr. Mazzarelli shows how different lesions within the same patient—and even within a single tumor—may demonstrate variable PSMA expression, diffusion restriction, and enhancement patterns, often correlating with differences in Gleason grade and tumor biology. He also discusses scenarios in which clinically significant prostate cancer may demonstrate low or absent PSMA uptake, underscoring the limitations of PSMA PET in certain histologic subtypes and advanced disease states.

The case series reinforces that MRI remains the gold standard for precise anatomic localization and local staging, while PSMA PET adds critical molecular sensitivity for nodal, osseous, and visceral disease. Together, these tools improve diagnostic confidence, support personalized treatment planning, and help clinicians better understand biologic heterogeneity in prostate cancer.