*2.2. Image Acquisition*

The mpMRI images were acquired on a Siemens Magnetom Trio 3-Tesla MRI scanner (Siemens AG, Munich, Germany) and a Phillips Ingenia 3-Tesla MRI scanner (Phillips Healthcare, Amsterdam, Netherlands) at the University of California, Irvine. The image acquisitions were completed in adherence to the prostate imaging reporting and data system (PI-RADS) v2 protocol without endorectal coil (Table 1).


**Table 1.** Magnetic resonance imaging (MRI) acquisition parameters.

### *2.3. Ground Truth Segmentation*

Ten radiologists manually segmented the prostate organ on axial T2-weighted (T2W) images with Profuse software (Eigen, Grass Valley, CA, USA). A board-certified abdominal radiologist with over 10 years of experience (R.H.) was the most experienced radiologist who approved each case. When other radiologists' segmentations differed from his expertise, he refined and updated those segmentations to establish the final ground truth. The mpMRI data and prostate organ segmentation data were transferred to a proprietary research database. From the database, the T2W axial images and organ segmentations were accessed and revised on an in-house image segmenting tool. The in-house tool enabled any segmentation corrections to be completed quickly. This tool integrated with the neural network training software and could be accessed with a web browser. Any segmentation updates were thus seamlessly updated into the neural network implementation.
