Deep learning based convolutional neural networks (CNNs) for prostate cancer (PCa) risk stratification employ radiologist delineated regions of interest (ROIs) on MRI. These ROIs contain the reader’s interpretation of the region of PCa. Variations in reader annotations change the features that are extracted from the ROIs, which may in turn affect classification performance of CNNs. In this study, we sought to analyze the effect of variations in inter-reader delineations of PCa ROIs on training of CNNs with regards to distinguishing clinically significant (csPCa) and insignificant PCa (ciPCa). We employed 180 patient studies (n=274 lesions) from 3 cohorts who underwent 3T multi-parametric MRI followed by MRI-targeted biopsy and/or radical prostatectomy. ISUP Gleason grade groups (GGG) obtained from pathology were used to determine csPCa (GGG≥2) and ciPCa (GGG=1). 5 experienced radiologists, with over 5 years of experience in prostate imaging, delineated PCa ROIs on bi-parametric MRI (bpMRI including T2 weighted (T2W) and diffusion weighted (DWI) sequences) within the training set (n1=160 lesions) using targeted biopsy locations. Patches were extracted using the ROIs which were then used to train individual CNNs (N1-N5) using the SqueezeNet architecture. The average volume for readerdelineated ROIs used for training varied greatly, ranging between 1106 and 2107 mm across all readers. The resulting networks showed no significant difference in classification performance (AUC= 0.82 ± 0.02) indicating that they were relatively robust to inter-reader variations in ROI. These models were evaluated on independent test sets (n2=85 lesions, n3=29 lesions) where ROIs were obtained by co-registration of MRI with post-surgical pathology, unaffected by inter-reader variations in ROIs. Network performance across D2 and D3 was 0.80±0.02 and 0.62 ± 0.03, respectively. The CNN predictions were moderately consistent, with ICC(2,1) scores across D2 and D3 being 0.74 and 0.54, respectively. Higher agreement in ROI overlap produced higher correlation in predictions on external test sets (R = 0.89, p < 0.05). Furthermore, higher average ROI volume produced greater AUC scores on D3, indicating that comprehensive ROIs may provide more features for DL networks to use in classification. Inter-reader variations in ROIs on MRI may influence the reliability and generalizability of CNNs trained for PCa risk stratification.
Periprostatic fat composition on T2-weighted (T2w) MRI has been shown to be associated with aggressive prostate cancer and may influence extraprostatic extension (EPE). In this study, we interrogate the periprostatic fat (PPF) region adjacent to cancer lesion on prostate T2w MRI. Patients with pathologic stage ≥ pT3a are considered to experience EPE (EPE+) and those with stage ≤ T2c are without EPE (EPE-) post radical prostatectomy (RP). We use a cohort of N = 45 prostate cancer patients retrospectively acquired from a single institution who underwent 3T multi-parametric MRI prior to RP. Radiomic features including 1st and 2nd order statistics, Haralick, Gabor, CoLlAGe features are extracted from a region of interest (ROI) in the PPF on pre-surgical T2w MRI delineated by an experienced radiologist. Haralick, gradient and CoLlAGe features were observed to be significantly different (p<0.05) in PPF ROIs between EPE+ and EPE- and were significantly over expressed in EPE+ patients compared to EPE- patients, suggesting a higher heterogeneity within the PPF region for EPE+ patients. These features were used to train machine learning classifiers using a 3-fold cross validation approach in conjunction with feature selection methods to predict EPE. The best classification performance was obtained with Support Vector Machine (SVM) classifiers resulting in an AUC = 0.88 (±0.04). On univariable and multivariable analysis, we observed that radiomic classifier predictions resulted in significant separation between EPE+ and EPE- while none of the routinely used clinical parameters including prostate specific antigen (PSA), Gleason Grade Groups (GGG), age, race and prostate imaging reporting and data system (PI-RADS v2) scores showed significant differences. Our results suggest that radiomic features may quantify the underlying heterogeneity in periprostatic fat and predict patients who are likely to experience extraprostatic extension of disease post RP.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.