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Towards a 3D Ultrasound Needle Guidance System for High-Dose-Rate Interstitial Gynecologic Brachytherapy Implant Placements

J Rodgers*1, J Bax1 , K Surry2 , W Hrinivich3 , E Leung4 , V Velker2 , D D'Souza2 , A Fenster1 , (1) Robarts Research Institute, Western University, London, ON, (2) London Regional Cancer Program, London, ON, (3) Johns Hopkins University School of Medicine, Baltimore, MD, (4) Odette Cancer Centre, Toronto, ON

Presentations

(Saturday, 3/30/2019) 10:30 AM - 12:30 PM

Room: Osceola Ballroom C

Purpose: To design a 3D ultrasound (US) system for intraoperative implant assessment during high-dose-rate interstitial brachytherapy (ISBT) of gynecologic cancers, with the potential to improve implant quality and reduce risk to nearby organs-at-risk (OAR).

Methods: The system incorporates two scanning geometries, 3D transrectal US (TRUS) and 360° 3D sidefire transvaginal US (TVUS), to account for the challenging presentations of gynecologic malignancies. The technique uses a 2D US probe, rotated to acquire a 3D image in < 20 s. TRUS and TVUS modes were tested in five and six patients, respectively, where needle positions were compared against clinical post-insertion CT images. An automatic segmentation algorithm using a modified randomized 3D Hough transform to simultaneously identify multiple needles was tested with one TVUS image containing eight needles as a proof-of-concept for needle localization in the TVUS images.

Results: Comparison of 58 needles between TRUS and registered CT images demonstrated a mean ± standard deviation tip position difference of 3.82 ± 1.62 mm and mean angular difference of 3.04 ± 1.63°. Similarly, the mean maximum positional difference was 2.36 ± 0.97 mm and mean angular difference was 1.95 ± 0.70° for 54 needles in the TVUS images. The algorithm identified all needles with a mean maximum position difference of 0.78 ± 0.17 mm and mean angular difference of 0.44 ± 0.19°. Additionally, nearby OAR were clearly visible in most images, including the rectum in the TVUS images and bladder in TRUS and TVUS images.

Conclusion: Despite the variable presentation of gynecologic cancers and necessity for precise placement of needles to deliver optimal dose during ISBT, there is currently no standard method to visualize the implant intraoperatively. The proposed system provides the potential for a versatile method to assess the implant during needle placement, allowing needles and nearby OAR to be visualized and localized.

Funding Support, Disclosures, and Conflict of Interest: This work was funded by the Ontario Institute of Cancer Research (OICR), the Canadian Institutes of Health Research (CIHR), and the Natural Sciences and Engineering Research Council of Canada (NSERC). We have no other conflicts of interest or disclosures.

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