Clinical implementation of 3D transvaginal ultrasound for intraoperative guidance of needle implant in template interstitial gynecologic high-dose-rate brachytherapy

PURPOSE: To demonstrate novel clinical implementation of a 3D transvaginal ultrasound (3DTVUS) system for intraoperative needle insertion guidance in perineal template interstitial gynecologic high-dose-rate brachytherapy and assess its impact on implant quality. METHODS AND MATERIALS: Interstitial implants began with preimplant 3DTVUS to visualize the tumor and anatomy, with intermittent 3DTVUS to assess the implant and guide needle adjustment. Analysis includes visualization of the implant relative to anatomy, identification of cases where 3DTVUS is beneficial, dosimetry, and a survey distributed to 3DTVUS clinicians. RESULTS: Seven patients treated between November 2021 and October 2022 were included in this study. Twenty needles were inserted under 3DTVUS guidance. The tumor and vaginal wall were well-differentiated in four and all seven patients, respectively. Patients with tumours below the superior aspect of the vagina are suited for 3DTVUS. Four radiation oncologists responded to the survey. There was general agreement that 3DTVUS improves implant and anatomy visualization and is preferred over standard 2D ultrasound guidance techniques. CONCLUSIONS: Based on qualitative feedback from primary users and a small preliminary patient cohort, 3DTVUS imaging improves tumor and vaginal wall visualization during gynecologic perineal template interstitial needle implant and is a powerful tool for implant assessment in an intraoperative setting.