Automated Patient-level Prostate Cancer Detection with Quantitative Diffusion Magnetic Resonance Imaging

BACKGROUND: Multiparametric magnetic resonance imaging (mpMRI) improves detection of clinically significant prostate cancer (csPCa), but the subjective Prostate Imaging Reporting and Data System (PI-RADS) system and quantitative apparent diffusion coefficient (ADC) are inconsistent. Restriction spectrum imaging (RSI) is an advanced diffusion-weighted MRI technique that yields a quantitative imaging biomarker for csPCa called the RSI restriction score (RSI(rs)). OBJECTIVE: To evaluate RSI(rs) for automated patient-level detection of csPCa. DESIGN, SETTING, AND PARTICIPANTS: We retrospectively studied all patients (n = 151) who underwent 3 T mpMRI and RSI (a 2-min sequence on a clinical scanner) for suspected prostate cancer at University of California San Diego during 2017–2019 and had prostate biopsy within 180 d of MRI. INTERVENTION: We calculated the maximum RSI(rs) and minimum ADC within the prostate, and obtained PI-RADS v2.1 from medical records. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We compared the performance of RSI(rs), ADC, and PI-RADS for the detection of csPCa (grade group ≥2) on the best available histopathology (biopsy or prostatectomy) using the area under the curve (AUC) with two-tailed α = 0.05. We also explored whether the combination of PI-RADS and RSI(rs) might be superior to PI-RADS alone and performed subset analyses within the peripheral and transition zones. RESULTS AND LIMITATIONS: AUC values for ADC, RSI(rs), and PI-RADS were 0.48 (95% confidence interval: 0.39, 0.58), 0.78 (0.70, 0.85), and 0.77 (0.70, 0.84), respectively. RSI(rs) and PI-RADS were each superior to ADC for patient-level detection of csPCa (p < 0.0001). RSI(rs) alone was comparable with PI-RADS (p = 0.8). The combination of PI-RADS and RSI(rs) had an AUC of 0.85 (0.78, 0.91) and was superior to either PI-RADS or RSI(rs) alone (p < 0.05). Similar patterns were seen in the peripheral and transition zones. CONCLUSIONS: RSI(rs) is a promising quantitative marker for patient-level csPCa detection, warranting a prospective study. PATIENT SUMMARY: We evaluated a rapid, advanced prostate magnetic resonance imaging technique called restriction spectrum imaging to see whether it could give an automated score that predicted the presence of clinically significant prostate cancer. The automated score worked about as well as expert radiologists’ interpretation. The combination of the radiologists’ scores and automated score might be better than either alone.