ESTRO 2024 - Abstract Book

S2346

Clinical - Urology

ESTRO 2024

Ten independent observers delineated the prostatic urethra in ten cases from the PACE-C study on 2.5 mm slice thickness T2- weighted MRI. Each observer’s urethral delineation was compared against an expert reference contour by calculating the dice similarity coefficient (DSC), mean distance to agreement (MDTA) and Hausdorff distance (HD). The observers then received a training intervention, which included a radiologist-led teaching session on urethra delineation and provision of a urethra contouring guideline. The observers later delineated the prostatic urethra in ten different cases. The Wilcoxon signed-rank test was used to assess a significant difference between DSC, MDTA, and HD before and after the training intervention for each observer and the overall group.

Results:

The observers had a median of 6 years’ (IQR 3 -12) experience in genitourinary contouring. The median DSC for the ten observers pre- and post-training intervention was 0.40 (IQR 0.27-0.49) and 0.50 (IQR 0.38-0.58) respectively, p<0.0001. The median MDTA pre- and post-training intervention was 0.12 mm (IQR 0.10-0.17) and 0.11 mm (IQR 0.08-0.14) respectively, p=0.02. The median HD pre- and post-training intervention was 0.50 (IQR 0.40-0.62) and 0.49 mm (IQR 0.39-0.61), respectively, p=0.99. The greatest variability occurs between the mid-gland and base of the prostate.

Conclusion:

The prostatic urethra is a challenging structure to contour with marked inter-observer variability. Attendance at a radiologist-led training session and provision of a urethral contouring guideline improved delineation accuracy.

Keywords: Urethra, Contouring, prostate radiotherapy