Gantry triggered x-ray verification during single-isocenter stereotactic radiosurgery: Increased certainty for a no-margin strategy.

Autor: Gutiérrez A; Department of Radiotherapy, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium. Electronic address: adrian.gutierrez@uzbrussel.be., Gevaert T; Department of Radiotherapy, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium., Boussaer M; Department of Radiotherapy, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium., Everaert T; Department of Radiotherapy, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium., Ferro Teixeira C; Department of Radiotherapy, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium., De Ridder M; Department of Radiotherapy, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium.
Jazyk: angličtina
Zdroj: Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology [Radiother Oncol] 2023 Sep; Vol. 186, pp. 109808. Date of Electronic Publication: 2023 Jul 17.
DOI: 10.1016/j.radonc.2023.109808
Abstrakt: Background: Single-isocenter linac-based stereotactic radiosurgery (SRS) has emerged as a dedicated treatment option for multiple brain metastases. Consequently, image-guidance for patient positioning and motion management has become very important. The purpose of this study was to analyze intra-fraction errors measured with stereoscopic x-rays and their impact on the dose distribution.
Materials and Methods: Treatments were planned with non- coplanar dynamic conformal arcs for 33 patients corresponding to 127 brain lesions and 356 arcs. Intra-arc positioning errors were measuredusing stereoscopic x-rays (ExacTrac Dynamic, Brainlab), triggered during arc delivery. Couch corrections above 0.7 mm and 0.5° were always applied. Intra-arc positioning data was analyzed. The dose impact was evaluated by applying the measured errors to the dose given in each arc.
Results: Median residual errors were 0.10 mm, 0.13 mm and 0.08 mm for the lateral, longitudinal and vertical directions and 0.10°, 0.08° and 0.13° for the pitch, roll and yaw angles respectively. 90% of the treatment arcs showed shifts of less than 0.4 mm and 0.4°in all directions. Dosimetric impact of motion showed the largest losses in coverage on small targets. All targets achieved at least 95% of the prescription dose to 95% of their volume, even when planned without margins.
Conclusions: Intra-fractional errors measured during beam delivery were found to be notably low with a dose impact that showed acceptable target coverage when applying these intra-arc errors to the dose distributions of the individual treatment arcs. Using an adequate immobilization and intra-fraction imaging prior to and during irradiation, no margins need to be added to compensate for intra-fraction motion.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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