Online

WCB 2021 - Online

Session Item

Friday
May 07
08:45 - 10:00
Brachytherapy physics 2030 – Enhanced application and in-vivo treatment verification
0150
Symposium
09:21 - 09:39
In vivo HDR brachytherapy source tracking with point dosimeters: current status and future directions
Joel Poder, Australia
SP-0056

Abstract

In vivo HDR brachytherapy source tracking with point dosimeters: current status and future directions
Authors: Joel Poder(St George Hospital Cancer Care Centre, Department of Medical Physics, Sydney, Australia), Dean Cutajar(University of Wollongong, Centre for Medical Radiation Physics, Wollongong, Australia), Andrew Howie(St George Hospital Cancer Care Centre, Department of Medical Physics, Sydney, Australia), Marco Petasecca(University of Wollongong, Centre for Medical Radiation Physics, Wollongong, Australia), Michael Lerch(University of Wollongong, Centre for Medical Radiation Physics, Wollongong, Australia), Joseph Bucci(St George Hospital Cancer Care Centre, Department of Radiation Oncology, Sydney, Australia), Anatly Rosenfeld(University of Wollongong, Centre for Medical Radiation Physics, Wollongong, Australia)
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Abstract Text

Brachytherapy has been proven to be an effective radiotherapy modality for a number of treatment sites including the breast, prostate and cervix. However, it is also recognized that amongst patients who have received brachytherapy as part of their treatment that up to 15% of such procedures may result in sub-optimal dose distributions.

There has therefore been an increased focus within the brachytherapy community in recent years towards more comprehensive treatment validation. One form of treatment validation that is beginning to be utilized is in-vivo source tracking, through the use of either two-dimensional detector arrays or single point detectors.

A review of the literature reveals that in-vivo source tracking techniques using two-dimensional arrays placed beneath a patient have been shown to have the ability to track the brachytherapy source to within 2 mm relative to the patient anatomy, whilst detector arrays integrated into transrectal ultrasound imaging devices can measure a dwell position with sub-millimetre accuracy, and point detectors placed within a catheter or on an applicator have measured shifts in dwell positions (relative to the detector) on the order of 0.5 mm.

In this talk I will discuss the potential advantages of in-vivo source tracking using point dosimeter arrays as compared to performing in-vivo dosimetry, particularly in the context of the steep dose gradients experienced in brachytherapy. Desirable detector properties for performing in-vivo source tracking will be outlined, with particular reference to the angular dependence and detector sensitivity.

I will also give an overview of the evolution and current status of novel detector systems developed at the Centre for Medical Radiation Physics that have been applied to in-vivo source tracking in HDR brachytherapy at St George Cancer Care Centre, Sydney and the Fondazione IRCCS Istituto Nazionale Tumori, Milan.

Finally, beyond the suitability of the detector type selected for in-vivo source tracking, there are several additional practical and philosophical challenges that must be overcome when implementing a successful in-vivo source tracking system. For example, the question of what is an appropriate in-vivo source tracking error threshold. I’ll conclude this talk by presenting the current status of in-vivo source tracking in overcoming these challenges and discuss the outlook of in-vivo source tracking for HDR brachytherapy as the community moves towards more comprehensive treatment validation.