STereotactic Arrhythmia Radioablation in Europe–Treatment Unit QA Audit of the STOPSTORM Consortium
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Abstract
STereotactic Arrhythmia Radioablation in Europe–Treatment Unit QA Audit of the STOPSTORM Consortium
Authors: Łukasz Dolla1, Aleksandra Grządziel1, Adam Bekman2, Sławomir Blamek3, Tomasz Latusek3, Marcin Miszczyk4, Joost J. Verhoeff5, Melanie Grehn6, Oliver Blanck6
1Maria Skłodowska-Curie National Research Institute of Oncology, Gliwice branch, Radiotherapy Planning Department, Gliwice, Poland; 2Maria Skłodowska-Curie National Research Institute of Oncology, Gliwice branch, Medical Physics Department, Gliwice, Poland; 3Maria Skłodowska-Curie National Research Institute of Oncology, Gliwice branch, Radiotherapy Department, Gliwice, Poland; 4Maria Skłodowska-Curie National Research Institute of Oncology, Gliwice branch, IIIrd Department of Radiotherapy and Chemotherapy, Gliwice, Poland; 5University Medical Center Utrecht, Department of Radiotherapy, Utrecht, The Netherlands; 6University Medical Center Schleswig-Holstein, Department of Radiation Oncology, Kiel, Germany
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Purpose or Objective
In patients with refractory ventricular tachycardia (VT), STereotactic Arrhythmia Radioablation (STAR) showed promising results for otherwise untreatable patients. The STOPSTORM project coordinates European efforts to validate STAR and refine protocols and guidelines for treatment harmonization. Major impact on harmonization results from treatment unit quality control procedures and we now present the current SBRT and STAR practice in Europe for machine and patient-specific quality assurance (QA) based on a comprehensive audit survey.
Material and Methods
The treatment unit QA audit survey included comprehensive items on machine characteristics and commissioning, dosimetric and geometric QA, imaging system QA, end-2-end tests and patient-specific plan verification. The audit was addressed to all STOPSTORM project participants and was mandatory for prospective patient inclusion into the STOPSTORM database.
Results
23 centers with 28 treatment units (C-arm LINAC, CyberKnife, MRidian and Synchrotron) using mostly 6-10 FFF beams collimated by MLCs with leaves from 2.5 to 10 mm or cones from 5-60mm participated in the audit survey. Eight different reference and four different small field dosimetry protocols with 14 different types of detectors are used for system commissioning and absolute dose calibration. Absolute dosimetry for reference fields is verified with an accuracy of 1% - 2%, with a frequency from daily to yearly. Furthermore, most participants perform external dosimetry audits. Planning CT quality parameters are tested regularly, and the hounds field curve stability is mostly verified on a yearly basis. Treatment unit geometric and isocenter tests (mechanical and Winston-Lutz tests) are mostly performed with different frequencies. The various imaging systems (kV, MV, CBCT, ExacTrac, Catalyst, IsoCrystal, MRI) are tested with static and reposition tests, however, image quality is mostly validated during commissioning or maintenance and less frequently on a regular basis performed by the participants itself. A system specific end-2-end test is implemented by only 65.2% of the participants, performed from monthly to yearly, while even fewer (34.7%) centers included motion simulation in this test. For patient-specific QA, 20 centers use 2D or 3D evaluation methods, however, with varying phantoms, detectors, and criteria.
Conclusion
This STOPSTORM multi-center treatment unit audit survey provided data concerning current quality assurance practices in major European centers performing SBRT and STAR. Notable differences and even deficiencies were identified in small-field dosimetry, external audits, image guidance verification, particularly in repositioning tests and image quality assessment both on the treatment unit and on the CT scanner, end-2-end tests and patient specific-plan verification. Based on the audit, recommendations were issued to harmonize quality assurance procedures for STAR within the STOPSTORM project.