A multicenter end-to-end postal audit of skin markerless surface-guided radiation therapy.
20 affiliations
- 1Department of Therapeutic Radiology, University of Yamanashi, Yamanashi, Japan.
- 2Department of Radiation Oncology, St. Luke's International Hospital, Tokyo, Japan.
- 3Department of Radiology, Kanazawa University Hospital, Ishikawa, Japan.
- 4Department of Radiological Technology, Kumamoto University Hospital.
- 5Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
- 6Department of Radiology, Kagoshima University Hospital, Kagoshima, Japan.
- 7Department of Radiology, Teikyo University Hospital, Tokyo, Japan.
- 8Department of Radiological Sciences, Komazawa University, Tokyo, Japan.
- 9Department of Radiation Therapy, Tokyo Medical University Hospital, Tokyo, Japan.
- 10Department of Radiation Oncology, Chiba Tokushukai Hospital, Chiba, Japan.
- 11Department of Radiology, Hamamatsu University School of Medicine, Shizuoka, Japan.
- 12Regional Creative Education Center, Hamamatsu University School of Medicine, Shizuoka, Japan.
- 13Department of Radiation Oncology, Tokyo Women's Medical University, Tokyo, Japan.
- 14Division of Medical Physics, School of Medical Sciences, Fujita Health University, Aichi, Japan.
- 15Department of Radiology, Seirei Hamamatsu General Hospital, Shizuoka, Japan.
- 16Department of Radiation Oncology, Aichi Cancer Center, Aichi, Japan.
- 17Division of clinical radiology service, Kyoto University Hospital, Kyoto, Japan.
- 18Division of Clinical Radiology, Department of Medical Technology, Kagawa University Hospital, Kagawa, Japan.
- 19Department of Radiological Technology, Faculty of Medical Technology, Teikyo University, Tokyo, Japan.
- 20Faculty of Health Science, Juntendo University, Tokyo, Japan.
Abstract
Background
Surface-guided radiation therapy (SGRT) enables skin markerless positioning, but its accuracy may depend on the reference surface, hardware configuration, commissioning, and institutional workflow. Two reference surfaces are commonly used: a DICOM reference generated from planning CT images and an SGRT reference acquired in the treatment room. Multicenter end-to-end data across commercial systems remain limited.Purpose
To evaluate static irradiation accuracy and setup time with two reference surfaces in a nationwide multicenter skin markerless SGRT postal audit.Methods
A prospective end-to-end postal audit was conducted from October 2023 to July 2025 at 40 Japanese institutions using five commercial SGRT systems (AlignRT, Catalyst, ExacTrac Dynamic, IDENTIFY, and VOXELAN), eight per system. Each institution received a common phantom package: a breast-shaped surface phantom, two cubic phantoms containing gold markers, and radiochromic films. Markerless setup and irradiation were performed with both the DICOM and SGRT references; ExacTrac Dynamic institutions performed the DICOM reference setup only. Static irradiation accuracy was the difference between the film-derived radiation center and the intended center in the DICOM RT Plan; the primary metric was the three-dimensional translational vector error (3D vector error). Paired comparisons used the Wilcoxon signed-rank test, and multivariable linear regression evaluated factors associated with both endpoints.Results
Critical setup errors exceeding 5 mm occurred at four institutions initially (institution-level error rate, 10.0%; three with the DICOM and one with the SGRT reference); one DICOM reference setup was not remeasured and remained out of tolerance, and was excluded as an outlier, leaving 39 DICOM and 31 SGRT reference setups for analysis. Excluding ExacTrac Dynamic, the DICOM reference showed a significantly larger 3D vector error than the SGRT reference (1.54 ± 0.91 vs. 1.20 ± 0.61 mm, p = 0.043). Setup time did not differ between references (86.19 ± 43.57 vs. 81.61 ± 37.09 s, p = 0.804). Axis-specifically, the difference between references was confined to the anterior-posterior direction (mean absolute difference 0.36 mm, p = 0.002), whereas a caudal superior-inferior offset was present with both (-0.50 ± 1.29 and -0.37 ± 0.87 mm; both p < 0.01) and did not differ between them (p = 0.854). The 1-camera condition was independently associated with a larger 3D vector error than the 3-camera condition (β = 0.90 mm; 95% CI, 0.17-1.63 mm; p = 0.017); no factor was associated with setup time, which showed no correlation with 3D vector error.Conclusions
Skin markerless SGRT achieved millimeter-level static irradiation accuracy but carried a non-negligible risk of critical setup errors. The difference between the two reference workflows was confined to the anterior-posterior direction, whereas a superior-inferior offset common to both indicates a residual uncertainty in the audit chain itself. Reference surface selection and camera configuration influenced accuracy, whereas setup time was not a reliable surrogate. These findings highlight the importance of commissioning, standardized reference surface acquisition, routine QA, and independent third-party audits.
Related
- Surface-guided Radiation Therapy in Clinical Practice: A Review with Perspectives on Implementation in Resource-constrained Settings
- A simple flux criterion for trapped surface formation by short pulses of gravitational radiation and matter
- Advances in Stereotactic Body Radiation Therapy: Expanding Clinical Applications and Improving Treatment Precision
- Effect of Near-surface Thermal Spikes on Radiation Hardness of Gallium Oxide
- AAPM Medical Physics Practice Guideline 18.a: Superficial radiation therapy using low-energy kilovoltage x-rays.
BibTeX
@article{saito2026multicenter,
title = {{A multicenter end-to-end postal audit of skin markerless surface-guided radiation therapy.}},
author = {Masahide Saito and Ryohei Yamauchi and Hironori Kojima and Yoshinobu Shimohigashi and Takeshi Ono and Yoshifumi Oku and Shinobu Kumagai and Naoki Tohyama and Masahiko Kurooka and Eriko Saito and Masataka Sakamoto and Yusuke Ueshima and Takayuki Kanai and Naoki Hayashi and Tatsunori Saito and Tomoki Kitagawa and Makoto Sasaki and Hiroki Katayama and Hidekazu Suzuki and Chie Kurokawa and Hiroshi Onishi},
journal = {Journal of applied clinical medical physics},
year = {2026},
month = oct,
doi = {10.1002/acm2.70893},
url = {https://europepmc.org/article/MED/42958617},
note = {CC BY},
}
RIS
TY - JOUR
TI - A multicenter end-to-end postal audit of skin markerless surface-guided radiation therapy.
AU - Masahide Saito
AU - Ryohei Yamauchi
AU - Hironori Kojima
AU - Yoshinobu Shimohigashi
AU - Takeshi Ono
AU - Yoshifumi Oku
AU - Shinobu Kumagai
AU - Naoki Tohyama
AU - Masahiko Kurooka
AU - Eriko Saito
AU - Masataka Sakamoto
AU - Yusuke Ueshima
AU - Takayuki Kanai
AU - Naoki Hayashi
AU - Tatsunori Saito
AU - Tomoki Kitagawa
AU - Makoto Sasaki
AU - Hiroki Katayama
AU - Hidekazu Suzuki
AU - Chie Kurokawa
AU - Hiroshi Onishi
PY - 2026
DA - 2026/10/29
JO - Journal of applied clinical medical physics
DO - 10.1002/acm2.70893
UR - https://europepmc.org/article/MED/42958617
AB - Background Surface-guided radiation therapy (SGRT) enables skin markerless positioning, but its accuracy may depend on the reference surface, hardware configuration, commissioning, and institutional workflow. Two reference surfaces are commonly used: a DICOM reference generated from planning CT images and an SGRT reference acquired in the treatment room. Multicenter end-to-end data across commercial systems remain limited.Purpose To evaluate static irradiation accuracy and setup time with two reference surfaces in a nationwide multicenter skin markerless SGRT postal audit.Methods A prospective end-to-end postal audit was conducted from October 2023 to July 2025 at 40 Japanese institutions using five commercial SGRT systems (AlignRT, Catalyst, ExacTrac Dynamic, IDENTIFY, and VOXELAN), eight per system. Each institution received a common phantom package: a breast-shaped surface phantom, two cubic phantoms containing gold markers, and radiochromic films. Markerless setup and irradiation were performed with both the DICOM and SGRT references; ExacTrac Dynamic institutions performed the DICOM reference setup only. Static irradiation accuracy was the difference between the film-derived radiation center and the intended center in the DICOM RT Plan; the primary metric was the three-dimensional translational vector error (3D vector error). Paired comparisons used the Wilcoxon signed-rank test, and multivariable linear regression evaluated factors associated with both endpoints.Results Critical setup errors exceeding 5 mm occurred at four institutions initially (institution-level error rate, 10.0%; three with the DICOM and one with the SGRT reference); one DICOM reference setup was not remeasured and remained out of tolerance, and was excluded as an outlier, leaving 39 DICOM and 31 SGRT reference setups for analysis. Excluding ExacTrac Dynamic, the DICOM reference showed a significantly larger 3D vector error than the SGRT reference (1.54 ± 0.91 vs. 1.20 ± 0.61 mm, p = 0.043). Setup time did not differ between references (86.19 ± 43.57 vs. 81.61 ± 37.09 s, p = 0.804). Axis-specifically, the difference between references was confined to the anterior-posterior direction (mean absolute difference 0.36 mm, p = 0.002), whereas a caudal superior-inferior offset was present with both (-0.50 ± 1.29 and -0.37 ± 0.87 mm; both p < 0.01) and did not differ between them (p = 0.854). The 1-camera condition was independently associated with a larger 3D vector error than the 3-camera condition (β = 0.90 mm; 95% CI, 0.17-1.63 mm; p = 0.017); no factor was associated with setup time, which showed no correlation with 3D vector error.Conclusions Skin markerless SGRT achieved millimeter-level static irradiation accuracy but carried a non-negligible risk of critical setup errors. The difference between the two reference workflows was confined to the anterior-posterior direction, whereas a superior-inferior offset common to both indicates a residual uncertainty in the audit chain itself. Reference surface selection and camera configuration influenced accuracy, whereas setup time was not a reliable surrogate. These findings highlight the importance of commissioning, standardized reference surface acquisition, routine QA, and independent third-party audits.
SN - 1526-9914
ER -