Seed localization and TRUS-fluoroscopy fusion for intraoperative prostate brachytherapy dosimetry

Abstract

Objective: To develop and evaluate an integrated approach to intra-operative dosimetry for permanent prostate brachytherapy (PPB) by combining a fluoroscopy-based seed localization routine with a transrectal ultrasound (TRUS)-to-fluoroscopy fusion technique. Materials and Methods: Three-dimensional seed coordinates are reconstructed based on the two-dimensional seed locations identified from three fluoroscopic images acquired at different angles. A seed-based registration approach was examined in both simulation and phantom studies to register the seed locations identified from the fluoroscopic images to the TRUS images. Dose parameters were then evaluated and compared to CT-based dosimetry from a patient dataset. Results: Less than 0.2% error in the D90 value was observed using the TRUS-fluoroscopy image-fusion-based method relative to the CT-based post-implantation dosimetry. In the phantom study, an average distance of 3 mm was observed between the seeds identified from TRUS and the reconstructed seeds at registration. Isodose contours were displayed superimposed on the TRUS images. Conclusions: Promising results were observed in this preliminary study of a TRUS-fluoroscopy fusion-based brachytherapy dosimetry analysis method, suggesting that the method is highly sensitive and calculates clinically relevant dosimetry, including the prostate D90. Further validation of the method is required for eventual clinical application.

Image fusion techniques in permanent seed implantation

“…Su et al [69, 70] describe a fluoroscopic to TRUS fusion-based approach for intraoperative prostate brachytherapy dosimetry. Seed images were identified from multiple fluoroscopic images and reconstructed to determine the 3D distribution.…”

Feasibility of vibro‐acoustography with a quasi‐2D ultrasound array transducer for detection and localizing of permanent prostate brachytherapy seeds: A pilot ex vivo study

“…Currently, transrectal ultrasound (TRUS) and computed tomography (CT) imaging are the major imaging modalities used in image guidance and post-implant dosimetry dosimetry. [7][8][9][10][11] Different approaches relating to timing of planning and imaging in the preimplant, intraoperative, and post-implant settings have evolved and have been shown to be effective. 12 In considering further evolution and potential improvement in image guidance during permanent brachytherapy, an ideal imaging system would include portability, with simultaneous accurate needle and seed imaging, as well as prostate anatomy.…”

C-arm Pose Estimation in Prostate Brachytherapy by Registration to Ultrasound

“…Fusion of these complementary modalities would enable dynamic dosimetry. A variety of implant reconstruction techniques have been investigated [3,4,5] which share one common requirement: the relative poses of the fluoroscopy images must be known prior to reconstruction. The fluoroscopy pose is usually determined in one of three ways.…”

“…(a) Electronic joint encoder [3], rarely available as most facilities do not upgrade their vintage C-arms. (b) Optical tracker could localize the C-arm [4], which introduces prohibitive devices and logistical complexity in the otherwise streamlined clinical procedure. (c) Radiographic fiducials placed in the field of imaging, from which the pose of the fluoroscope can be discerned in relation to the fiducial structure [5].…”