Taylah Brennen
University of Wollongong
PhD Student

Marco Petasecca
Senior Lecturer
University of Wollongong

Dean Cutajar
Research Fellow
University of Wollongong

Saree Alnaghy
Postdoctoral Research Associate
University of Sydney

Joseph Bucci
Radiation Oncologist
St George Cancer Care Centre

Andrej Bece
Radiation Oncologist
St George Cancer Care Centre

Marco Favoino
Research
Advanced Computer System

Michael Lerch
Associate Professor
University of Wollongong

Anatoly Rosenfeld
Distinguished Professor
University of Wollongong

Introduction: BrachyView is a novel in-body imaging system developed with the objective to provide real-time intraoperative dosimetry for low dose rate prostate brachytherapy treatments. Seed positions can be reconstructed after implantation by the means of a high-resolution pinhole gamma camera. The obtained dataset is then combined with conventional trans-rectal ultrasound imaging (TRUS) to localise the effective implanted source position within the prostate volume1. Materials and Methods: The BrachyView probe consists of a 1mm thick tungsten cylindrical collimator, containing three single cone pinholes. This study utilised pinhole diameters of 500 µm and 800 µm to assess the effect of the pinhole diameter on seed reconstruction quality, as well as the feasibility to perform reconstruction prior to seed deployment from the treatment needles. Two clinical LDR prostate brachytherapy plans containing 98, and 96 seeds (I-125 with an average activity of 0.248mCi and 0.303mCi respectively), were implanted into a prostate gel phantom. TRUS images, manual segmentation and rendering were performed to reconstruct the 3D shape and position of the prostate, utilising transversal 2.5mm ultrasound slices. After each needles implantation, BrachyView data was obtained for an average of 2.5 minutes to compensate for the low activity seeds. As a gold standard reference for data comparison a post implant CT study was performed. Results: Comparison of CT and BrachyView data showed that average discrepancies of 2.4 mm, 1.35 mm and 1.2 mm in the x, y and z reference frames, respectively for the 500 µm collimator. Where average discrepancies of 4.3 mm, 4.8 mm and 2.5 mm in the x, y and z reference frames, respectively with the 800 µm collimator. Conclusions: A comparison of the BrachyView data utilising 500 µm and 800 µm pinhole diameters has allowed for optimisation of the collimator. 100% of seeds were reconstructed with use of the 500 µm collimator , with 74% within 2mm of their nominal positions. However due to the reduced pinhole size a longer acquisition time is required to obtain high quality projections. The 800 µm-data showed increased scatter contribution and reconstructed positions with large inaccuracy, where only 70% of seeds reconstructed. This indicates that use of the 800 µm collimator for seed reconstruction before seed deployment from treatment needles is not feasible with the current methodology. The combination of the 500 µm collimator and TRUS imaging has shown that it is a unique tool for intraoperative verification for implantation quality.


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