16-17 November 2023, Prague, Czech Republic
My experience with the brachytherapy physics quality assurance system (BRAPHYQS) within the framework of the 2023 Groupe Européen de Curiethérapie (GEC)-ESTRO workshop commenced with attending the 57th workgroup meeting. Even though it was held before the workshop began, the meeting was well attended; numerous interested attendees joined the group members and company representatives.
Co-ordinated by the group’s chair, Åsa Carlsson Tedgren (Sweden), the meeting began with updates from groups in which BRAPHYQS is represented or with which it liaises, including GEC-ESTRO, the ESTRO guidelines and physics committees, the ESTRO focus group on dosimetry and quality assurance (QA) and the American Association of Physicists in Medicine.
The progress of ongoing BRAPHYQS work packages was not discussed in detail, but interesting information was offered on the ongoing work on the second edition of the ESTRO Handbook of Brachytherapy and a special issue to be produced on brachytherapy in the open-access ESTRO journals, which will open to submissions in December.
The most interesting feature of the meeting was a presentation by Ruud van Leeuwen (The Netherlands) on whether report 58 from the International Commission on Radiation Units and Measurements, which is on dose and volume specifications for the reporting of interstitial therapy, should be updated. The presentation was followed by a discussion of whether or not to develop a work package on comparative dosimetry based on retrospective studies as a first step to advocating change. Dr van Leeuwen reported that various centres in The Netherlands had observed steadily increasing differences between source calibration certificates and corresponding clinical results. Although these differences are well below national and international action levels, the issue will be followed through by BRAPHYQS and its members who contributed to a corresponding guideline (DOI: 10.1016/j.radonc.2019.02.008).
An open BRAPHYQS meeting will be held at ESTRO 2024 and interested colleagues should consider attending.
During the workshop, the BRAPHYQS session was aimed to set the scene for a discussion on the evolution of technologies and clinical practice in brachytherapy.
Shirin Abbasi Nejad Enger (Canada) gave a brief outline of the principles and challenges of intensity-modulated brachytherapy (IMBT), as well as ongoing research and innovation initiatives that were intended to facilitate its integration into clinical practice. She pointed out that, in contrast to conventional brachytherapy, IMBT can provide highly conformal dose distributions and enhanced sparing of critical structures. However, its complexity has spurred rising demand for the development of sophisticated shielded applicators, delivery systems that involve rotating mechanisms and brachytherapy sources of appropriate energies and half-lives. Some of these have been applied successfully in clinical settings, while others remain in the form of digital models. Professor Enger also explained that the presence of high-density metal alloy heterogeneities in patient geometry necessitated the integration of model-based dose calculation algorithms or Monte Carlo simulation into treatment planning systems (TPSs) to enable the evaluation of IMBT treatment plans. She presented an overview of a Monte Carlo-based TPS for brachytherapy applications, the RapidBrachyMCTPS. She highlighted the dual functionality of this system as both a post-implant dosimetry package and as a TPS that can be used to generate and evaluate treatment plans, which is equipped with inverse planning optimisation algorithms that facilitate the clinical implementation of IMBT. Ongoing advances encompass the integration of intravascular brachytherapy applications and electronic brachytherapy dosimetry into RapidBrachyMCTPS; dosimetry based on artificial intelligence (AI); automated applicator digitisation; multi-objective optimisation; and fast segmentation with AI. It was impressive to hear that Monte Carlo results aligned remarkably with dose predictions produced through the use of convolutional neural networks for prostate and cervix brachytherapy applications, and achieved a 300-fold acceleration in dose calculations. Professor Enger summarised her presentation with the statement that a robust Monte Carlo-based TPS had been successfully developed; efforts were underway to develop an AI-based TPS; and IMBT for intracavitary cases had been prepared for clinical implementation, while potential radionuclides suitable for IMBT included 169Yb and 75Se.
Grzegorz Bieleda (Poland) led a discussion on the advances in 3D printing technology that pertained to high-dose-rate (HDR) brachytherapy applications. He said that integration of 3D printing into brachytherapy applications could increase spatial accuracy, streamline workflow and reduce costs without the need for advanced technological facilities or highly trained technicians, although correction of geometry errors could be challenging. He explained that incorporation of 3D printing into brachytherapy clinical practice entailed the assessment of the dosimetric impact of 3D-printing materials, the development of 3D-printing technology suitable for brachytherapy applicators, and the enhancement of QA tests for dose verification. The dosimetric impact of materials that are employed in stereolithography was discussed; their equivalence with water in 192Ir brachytherapy applications has been validated through experimental measurements in a 3D-printed phantom. A method for the preparation of 3D-printed applicators was described, and it was explained that corresponding film measurements in an anthropomorphic phantom had verified their suitability for brachytherapy applications. Concluding his presentation, Grzegorz Bieleda highlighted that preliminary clinical outcomes in skin and head-and-neck cases that had been treated with HDR brachytherapy using 3D-printed applicators had been favourable, as they had shown good local tumour control and low toxicity, while they had fitted well and ensured patient comfort.
To summarise, the BRAPHYQS lectures and discussions that were held within the framework of the 2023 GEC-ESTRO workshop provided a comprehensive overview of innovative ideas and cutting-edge technologies in brachytherapy. They suggested potential future benchmarks in the field.
Vasiliki Peppa
Medical physicist
Radiation Therapy Department, Alexandra Hospital
Post-PhD researcher
Medical Physics Laboratory,
National and Kapodistrian University of Athens
Greece
vpeppa@med.uoa.gr