Review of Prostate Imaging Reporting and Data System version 2

Relationship between Eccentricity and Volume Determined by Spectral Algorithms Applied to Spatially Registered Bi-Parametric MRI and Prostate Tumor Aggressiveness: A Pilot Study

(1) Background: Non-invasive prostate cancer assessments using multi-parametric MRI are essential to the reliable detection of lesions and proper management of patients. While current guidelines call for the administration of Gadolinium-containing intravenous contrast injections, eliminating such injections would simplify scanning and reduce patient risk and costs. However, augmented image analysis is necessary to extract important diagnostic information from MRIs. Purpose: This study aims to extend previous work on the signal to clutter ratio and test whether prostate tumor eccentricity and volume are indicators of tumor aggressiveness using bi-parametric (BP)-MRI. (2) Methods: This study retrospectively processed 42 consecutive prostate cancer patients from the PI-CAI data collection. BP-MRIs (apparent diffusion coefficient, high b-value, and T2 images) were resized, translated, cropped, and stitched to form spatially registered BP-MRIs. The International Society of Urological Pathology (ISUP) grade was used to judge cases of prostate cancer as either clinically significant prostate cancer (CsPCa) (ISUP ≥ 2) or clinically insignificant prostate cancer (CiPCa) (ISUP < 2). The Adaptive Cosine Estimator (ACE) algorithm was applied to the BP-MRIs, followed by thresholding, and then eccentricity and volume computations, from the labeled and blobbed detection maps. Then, univariate and multivariate linear regression fittings of eccentricity and volume were applied to the ISUP grade. The fits were quantitatively evaluated by computing correlation coefficients (R) and p-values. Area under the curve (AUC) and receiver operator characteristic (ROC) curve scores were used to assess the logistic fitting to CsPCa/CiPCa. (3) Results: Modest correlation coefficients (R) (>0.35) and AUC scores (0.70) for the linear and/or logistic fits from the processed prostate tumor eccentricity and volume computations for the spatially registered BP-MRIs exceeded fits using the parameters of prostate serum antigen, prostate volume, and patient age (R~0.17). (4) Conclusions: This is the first study that applied spectral approaches to BP-MRIs to generate tumor eccentricity and volume metrics to assess tumor aggressiveness. This study found significant values of R and AUC (albeit below those from multi-parametric MRI) to fit and relate the metrics to the ISUP grade and CsPCA/CiPCA, respectively.

Interobserver agreement of Prostate Imaging–Reporting and Data System (PI-RADS–v2)

Background

A retrospective study was conducted on 71 consecutive patients with suspected prostate cancer (PCa) with a mean age of 56 years and underwent mp-MRI of the prostate at 3 Tesla MRI. Two readers recognized all prostatic lesions, and each lesion had a score according to Prostate Imaging–Reporting and Data System version 2 (PI-RADS-v2).

Purpose of the study

To evaluate the interobserver agreement of PI-RADS-v2 in characterization of prostatic lesions using multiparametric MRI (mp-MRI) at 3 Tesla MRI.

Results

The overall interobserver agreement of PI-RADS-v2 for both zones was excellent (k = 0.81, percent agreement = 94.9%). In the peripheral zone (PZ) lesions are the interobserver agreement for PI-RADS II (k = 0.78, percent agreement = 83.9%), PI-RADS III (k = 0.66, percent agreement = 91.3 %), PI-RADS IV (k = 0.69, percent agreement = 93.5%), and PI-RADS V (k = 0.91, percent agreement = 95.7 %). In the transitional zone (TZ) lesions are the interobserver agreement for PI-RADS I (k = 0.98, percent of agreement = 96%), PI-RADS II (k = 0.65, percent agreement = 96%), PI-RADS III (k = 0.65, percent agreement = 88%), PI-RADS IV (k = 0.83, percent agreement = 96%), and PI-RADS V (k = 0.82, percent agreement = 92%).

Conclusion

We concluded that PI-RADS-v2 is a reliable and a reproducible imaging modality for the characterization of prostatic lesions and detection of PCa.

Online Interactive Case-Based Instruction in Prostate Magnetic Resonance Imaging Interpretation Using Prostate Imaging and Reporting Data System Version 2: Effect for Novice Readers

PURPOSE

To assess the effect on reader performance of an interactive case-based online tutorial for prostate magnetic resonance imaging (MRI) interpretation using Prostate Imaging and Reporting Data System (PI-RADS).

METHODS

An educational website was developed incorporating scrollable multiparametric prostate MRI examinations with annotated solutions based on PI-RADS version 2. Three second-year radiology residents evaluated a separate set of 60 prostate MRI examinations both before and after review of the online case material, identifying and scoring dominant lesions. These 60 examinations included 30 benign cases and 30 cases with a dominant lesion demonstrating Gleason score ≥3 + 4 tumor on fusion-targeted biopsy. The readers' pooled performance was compared between the 2 sessions using logistic regression and Wilcoxon signed rank tests.

RESULTS

All readers completed the online material within four-hours. Review of the online material significantly improved sensitivity (from 57.8%-73.3%, P = 0.003) and negative predictive value (from 69.2%-78.2%, P = 0.049), but not specificity (from 70.0%-67.8%, P = 0.692) or positive predictive value (from 59.6%-64.7%, P = 0.389). Reader confidence (1-10 scale; 10 = maximal confidence) also improved significantly (from 5.6 ± 2.7 to 6.3 ± 2.6, P = 0.026). However, accuracy of assigned PI-RADS scores did not improve significantly (from 45.5%-53.3%, P = 0.149).

CONCLUSION

An online interactive case-based website in prostate MRI interpretation improved novice readers' sensitivity and negative predictive value for tumor detection, as well as readers' confidence. This online material may serve as a resource complementing existing traditional methods of instruction by providing a more flexible educational experience among a larger volume of learners. However, further more targeted educational initiatives regarding the proper application of PI-RADS remain warranted.