Fig 1.
Patient’s enrollment flowchart.
At Institution A, 213 patients with a total of 274 lesions underwent biopsy from January 2017, to June 2017, and 142 patients with a total of 188 lesions underwent MRI from June 2017, to December 2017. At Institution B,143 patients with a total of 194 lesions who underwent MRI from June 2018, to November 2018, were enrolled in our study. Thirty-two patients with a total of 43 lesions were excluded because images were unavailable for analysis or MRI was incomplete. A total of 466 patients with a total of 613 lesions were evaluated in this study. Forty patients, each with 1 lesion (40 total lesions) were randomly selected from this cohort for the multireader study.
Fig 2.
Computed-based calculation for ADC values of lesion.
(a) Prostate cancer (Gleason score 4+3) in the left posterior peripheral zone of a 72-year-old man (left). On the ADC image, 3D-whole-lesion-ROI was placed encompassing the entire area of visually low ADC (right). (b) Schematic illustration of multiple overlapping 2D-small-ROIs (9 pixels), which were automatically generated within the 3D-whole-lesion-ROI. The kernel mask was used to average the neighbor pixels to the center pixel. The reference value was determined as the minimum of the multiple mean ADC values of all slices. (c) Histogram of ADC values measured by 3D-whole-lesion-ROI. The 10th percentile ADC values are shown. ADC indicates apparent diffusion coefficient; ROI, region of interest; 2D, two-dimensional; 3D, 3-dimensional.
Fig 3.
Bland-Altman plots of ADC values in each measurement method.
(a), Free 2D-small-ROI method. (b) 2D-small-ROI method with specific instruction to use 9-pixel 2D-small-ROI covering the lowest ADC area. (c) Tenth percentile of 3D-whole-lesion-ROI method. The x-axis is the average ADC value, whereas the y-axis is the difference between ADC value by each reader and the average ADC value. The 95% limits of agreement were ±205 (10−6 mm2/s) for the free 2D-small-ROI method, ±120 (10−6 mm2/s) for the 2D-small-ROI method with specific instruction, and ±112 (10−6 mm2/s) for 10th percentile of 3D-whole-lesion-ROI. ADC indicates apparent diffusion coefficient; ROI, region of interest; 2D, two-dimensional; 3D, 3-dimensional.
Table 1.
The results of the multi-reader study.