Spatial accuracy of dose delivery significantly impacts the planning target volume margin in linear accelerator-based intracranial stereotactic radiosurgery

Spatial accuracy of dose delivery significantly impacts the planning target volume margin in linear accelerator-based intracranial stereotactic radiosurgery

Abstract The impact of three-dimensional (3D) dose delivery accuracy of C-arm linacs on the planning target volume (PTV) margin was evaluated for non-coplanar intracranial stereotactic radiosurgery (SRS). A multi-institutional 3D starshot test using beams from seven directions was conducted at 22 cl...

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Main Authors: Yuta Takahashi, Riki Oshika, Rie Tachibana, Katsuyuki Shirai, Hiroshi Asakura, Masayoshi Miyazaki, Tomohiro Sagawa, Shinichi Takahashi, Tsunekazu Kuwae, Hironori Kojima, Shiro Nishiyama, Hikaru Nemoto, Yoshitomo Ishihara, Mariko Umeda, Kotaro Kijima, Daisuke Kobayashi, Keiji Suzuki, Yuki Nozawa, Kento Hoshida, Tomoki Kitagawa, Hiromitsu Endo, Yuki Matsunaga, Hiroya Itagaki, Mayumi Ishida, Shigeru Kanahara, Ryo Horita, Daisuke Hori, Hidenobu Tachibana
Format: Article
Language:English
Published: Nature Portfolio 2025-01-01
Series:Scientific Reports
Subjects:
SRS
Linac
Three-dimensional dose delivery accuracy
Margin size
Gel dosimeter
Multi-institution
Online Access:https://doi.org/10.1038/s41598-025-87769-z
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Summary:Abstract The impact of three-dimensional (3D) dose delivery accuracy of C-arm linacs on the planning target volume (PTV) margin was evaluated for non-coplanar intracranial stereotactic radiosurgery (SRS). A multi-institutional 3D starshot test using beams from seven directions was conducted at 22 clinics using Varian and Elekta linacs with X-ray CT-based polymer gel dosimeters. Variability in dose delivery accuracy was observed, with the distance between the imaging isocenter and each beam exceeding 1 mm at one institution for Varian and nine institutions for Elekta. The calculated PTV margins for Varian and Elekta linacs that could cover the gross tumor volume with 95% probability at 95% of the institutions were 2.3 and 3.5 mm, respectively, in the superior–inferior direction. However, with multifactorial system management (i.e., high-accuracy 3D dose delivery with rigorous linac quality assurance, strict patient immobilization, and high intra-fractional positioning accuracy), these margins could be reduced to 1.0 mm and 1.5 mm, respectively. The findings indicate significant millimeter-level variability in 3D dose delivery accuracy among linacs installed in clinical settings. Thus, maximizing a linac’s 3D dose delivery accuracy is essential to achieve the required PTV margin in intracranial SRS.
ISSN:2045-2322

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