Post hoc estimation of a quantitative restriction spectrum imaging biomarker for prostate cancer detection using conventional MRI.
Academic Article
Overview
abstract
BACKGROUND: Multiparametric MRI is useful for early detection of clinically significant prostate cancer (csPCa), but its standard apparent diffusion coefficient (ADC) has limited utility as a quantitative metric for automated, patient-level detection of csPCa. Restriction spectrum imaging (RSI), an advanced diffusion technique, yields a quantitative biomarker (RSIrs) that improves csPCa detection. RSIrs is typically calculated from a dedicated multi-b-value acquisition. RSIrs estimated from conventional MRI has not been studied. PURPOSE: To evaluate the accuracy and validity of RSI metrics estimated post hoc from conventional diffusion-weighted imaging (DWI) to serve as a viable surrogate for a dedicated RSI acquisition. MATERIALS AND METHODS: We conducted a retrospective, multicenter study of patients with both a dedicated RSI acquisition and conventional DWI. We compared three different RSI restriction score (RSIrs) calculation methods: from the dedicated acquisition (RSIrsdedicated), from conventional DWI alone (RSIrspost-hoc), and from a combination of conventional DWI with only the high b-values from the RSI acquisition (RSIrscombo). We compared these methods for quantitative agreement and csPCa detection performance (area under the receiver operating characteristic [AUC, 95% confidence interval]) of maximum RSIrs (RSIrsmax) in the prostate compared to that of minimum ADC (ADC). RESULTS: Data from n = 1095 patients (16 centers) were analyzed. Post hoc RSIrsmax differed systematically from RSIrsdedicated by a median of +156 (RSIrspost-hoc) and -59 (RSIrscombo), respectively. AUCs for csPCa detection were 0.51 [0.47,0.54], 0.60 [0.57,0.64], 0.70 [0.67,0.74], and 0.77 [0.74,0.80] for ADC, RSIrspost-hoc, RSIrscombo, and RSIrsdedicated, respectively. CONCLUSION: Even when estimated using conventional DWI, RSIrs is a superior quantitative biomarker to ADC for automated, patient-level detection of csPCa. A dedicated RSI acquisition gives the best performance. A compromise would be to acquire high b-values (1500 and 2500 s/mm2) to complement low b-values (<1000 s/mm2) from conventional DWI.
