Same-day repeatability and Between-Sequence reproducibility of Mean ADC in PI-RADS lesions

•ADC measurements in prostate lesions show notable variability.•For quantitative ADC assessment, 3D-ROIs are superior to 2D-ROIs.•The cut-off for measurement-based ADC variability is approx. 200 × 10-6 mm2/s (3D-ROIs)•Sequential ADC measurements are feasible by different raters or sequences.•Two DWI sequences demonstrate no significant bias and high comparability. This study aimed to assess repeatability after repositioning (inter-scan), intra-rater, inter-rater and inter-sequence variability of mean apparent diffusion coefficient (ADC) measurements in MRI-detected prostate lesions. Forty-three patients with suspicion for prostate cancer were included and received a clinical prostate bi-/multiparametric MRI examination with repeat scans of the T2-weighted and two DWI-weighted sequences (ssEPI and rsEPI). Two raters (R1 and R2) performed single-slice, 2D regions of interest (2D-ROIs) and 3D-segmentation-ROIs (3D-ROIs). Mean bias, corresponding limits of agreement (LoA), mean absolute difference, within-subject coefficient of variation (CoV) and repeatability/reproducibility coefficient (RC/RDC) were calculated. Bradley & Blackwood test was used for variance comparison. Linear mixed models (LMM) were used to account for multiple lesions per patient. Inter-scan repeatability, intra-rater and inter-sequence reproducibility analysis of ADC showed no significant bias. 3D-ROIs demonstrated significantly less variability than 2D-ROIs (p