Reproducibility of Index Lesion Size and Mean Apparent Diffusion Coefficient Values Measured by Prostate Multiparametric MRI: Correlation With Whole-Mount Sectioning of Specimens.

OBJECTIVE: The purpose of this study is to determine the intra- and interreader agreement for index lesion size and mean apparent diffusion coefficient (ADC) value measurements performed by five readers using whole-mount histopathologic specimens processed with a patient-specific, MRI-based, 3D-printed mold as the standard of reference. MATERIALS AND METHODS: All men who underwent multiparametric MRI of the prostate performed using a 3-T scanner with endorectal and phased-array surface coils, followed by prostatectomy conducted between November 2015 and July 2016 at our institution, were identified. MRI examinations were independently reviewed by five readers with varying degrees of experience, two of whom had essentially no experience in prostate MRI interpretation before the study, to assess index lesion size and ADC values. A linear mixed model-based intraclass correlation was used to assess intra- and interreader reader agreement for lesion size and ADC measurements and agreement for size measurements between pathologic analysis and readers. RESULTS: A total of 80 men met the study eligibility criteria. Overall inter- and intrareader agreement for ADC measurements was excellent, with interclass correlation coefficient (ICC) values of 0.84 and 0.90, respectively; both inter- and intrareader agreement between experienced readers (0.82 and 0.92, respectively) and inexperienced readers (0.86 and 0.87, respectively) were excellent as well. The agreement between mean lesion size on imaging and histopathologic analysis ranged from poor (0.32) to good (0.66), with overall agreement considered fair (0.49). CONCLUSION: Readers with varying degrees of experience achieved good-to-excellent agreement for index lesion size and ADC values on multiparametric MRI of men with prostate cancer. This degree of reproducibility may improve preoperative risk stratification, informed decision making, and treatment planning for men with known or suspected prostate cancer.

Diagnostic Utility of a Likert Scale Versus Qualitative Descriptors and Length of Capsular Contact for Determining Extraprostatic Tumor Extension at Multiparametric Prostate MRI.

OBJECTIVE: The purpose of this study is to determine the reproducibility and diagnostic performance of a Likert scale in comparison with the European Society of Urogenital Radiology (ESUR) criteria and tumor-pseudocapsule contact length (TCL) for the detection of extraprostatic extension (EPE) at multiparametric MRI. MATERIALS AND METHODS: This was a retrospective review of all men who underwent multiparametric MRI followed by prostatectomy between November 2015 and July 2016. Multiparametric 3-T MRI studies with an endorectal coil were independently reviewed by five readers who assigned the likelihood of EPE using a 1-5 Likert score, ESUR criteria, and TCL (> 10 mm). EPE outcome (absent or present) for the index lesion at whole-mount histopathologic analysis was the standard of reference. Odds ratios (ORs) and areas under the ROC curve (Az) were used for diagnostic accuracy. The interreader agreement was determined using a weighted kappa coefficient. A p < 0.05 was considered significant. RESULTS: Eighty men met the eligibility criteria. At univariate analysis, the Likert score showed the strongest association (OR, 1.8) with EPE, followed by prostate-specific antigen level (OR, 1.7), ESUR score (OR, 1.6), and index lesion size (OR, 1.2). At multivariable analysis, higher Likert score (OR, 1.8) and prostate-specific antigen level (OR, 1.6-1.7) were independent predictors of EPE. The Az value for Likert scores was statistically significantly higher (0.79) than that for TCL (0.74; p < 0.01), but not statistically significantly higher than the value for ESUR scores (0.77; p = 0.17). Interreader agreement with Likert (κ = 0.52) and ESUR scores (κ = 0.55) was moderate and slightly superior to that for TCL (κ = 0.43). Except for TCL among inexperienced readers (κ = 0.34), reader experience did not affect interreader agreement. CONCLUSION: A Likert score conveying the degree of suspicion at multiparametric MRI is a stronger predictor of EPE than is either ESUR score or TCL and may facilitate informed decision making, patient counseling, and treatment planning.

Improved Magnetic Resonance Imaging-Pathology Correlation With Imaging-Derived, 3D-Printed, Patient-Specific Whole-Mount Molds of the Prostate.

OBJECTIVES: The aim of this study was to compare the anatomical registration of preoperative magnetic resonance imaging (MRI) and prostate whole-mount obtained with 3D-printed, patient-specific, MRI-derived molds (PSM) versus conventional whole-mount sectioning (WMS). MATERIALS AND METHODS: Based on an a priori power analysis, this institutional review board-approved study prospectively included 50 consecutive men who underwent 3 T multiparametric prostate MRI followed by radical prostatectomy. Two blinded and independent readers (R1 and R2) outlined the contours of the prostate, tumor, peripheral, and transition zones in the MRI scans using regions of interest. These were compared with the corresponding regions of interest from the whole-mounted histopathology, the reference standard, using PSM whole-mount results obtained in the study group (n = 25) or conventional WMS in the control group (n = 25). The spatial overlap across the MRI and histology data sets was calculated using the Dice similarity coefficient (DSC) for the prostate overall (DSCprostate), tumor (DSCtumor), peripheral (DSCPZ), and transition (DSCTZ) zone. Results in the study and control groups were compared using Wilcoxon rank sum test. RESULTS: The MRI histopathology anatomical registration for the prostate gland overall, tumor, peripheral, and transition zones were significantly superior with the use of PSMs (DSCs for R1: 0.95, 0.86, 0.84, and 0.89; for R2: 0.93, 0.75, 0.78, and 0.85, respectively) than with the use of standard WMS (R1: 0.85, 0.46, 0.66, and 0.69; R2: 0.85, 0.46, 0.66, and 0.69) (P < 0.0001). CONCLUSIONS: The use of PSMs for prostate specimen whole-mount sectioning provides significantly superior anatomical registration of in vivo multiparametric MRI and ex vivo prostate whole-mounts than conventional WMS.