Impact of transperineal ultrasound on perineal skin dose in prostate radiation therapy

Kalani De Silva; Amy Brown; Christopher Edwards

doi:10.1016/j.tipsro.2022.08.003

Impact of transperineal ultrasound on perineal skin dose in prostate radiation therapy

Tech Innov Patient Support Radiat Oncol. 2022 Aug 27:23:27-32. doi: 10.1016/j.tipsro.2022.08.003. eCollection 2022 Sep.

Authors

Kalani De Silva¹, Amy Brown², Christopher Edwards¹

Affiliations

¹ School of Clinical Sciences, Queensland University of Technology, Gardens Point Campus, Brisbane, QLD, Australia.
² Townsville University Hospital, Townsville, Queensland, Australia.

Abstract

Introduction: This study investigated the relationship between anatomical compression introduced via ultrasound probe pressure and maximum perineum dose in prostate radiotherapy patients using the Clarity transperineal ultrasound (TPUS) system.

Methods: 115 patient ultrasound and computed tomography scans were retrospectively analysed. The probe to prostate apex distance (PPA), probe to inferior corpus spongiosum distance (PICS) and maximum perineum dose were calculated. Compression was represented by the PICS and the calculated corpus to prostate ratio (CPR). Demographics included treatment technique, image quality, body mass index (BMI) and age. Multiple linear regression analysis assessed the relationship between compression measures and perineum dose.

Results: The maximum dose to perineum ranged from 1.81 to 45.56 Gy, with a median of 5.87 Gy (Interquartile range (IQR) 3.17). The PICS distance and CPR recorded was 1.67 cm (IQR 0.63) and 0.51 (range 0.29-0.85) respectively. Regression analysis demonstrated both PICS and CPR were significant predictors of maximum dose to the perineum (p < 0.001). Patient-specific factors, including age, BMI, treatment technique and ultrasound image quality, were not factors that significantly impacted the maximum perineum dose.

Conclusion: There was a statistically significant association between increased anatomical compression and perineal dose measurements. A PICS of 1.2 cm or greater is recommended, with compression reduced as much as possible without losing anatomical US definition. Future investigations would be beneficial to evaluate the optimal balance between ultrasound image quality and transducer compression considering the perineum dose.

Keywords: CPR, Corpus to the prostate ratio; Image-guidance radiation therapy; PICS, Probe surface to inferior corpus spongiosum distance; PPA, Probe surface to prostate apex distance; Prostate cancer; Prostate intrafraction motion; TPUS, Transperineal Ultrasound; Transperineal ultrasound.