Quantifying Patient Setup Error in Total Body Irradiation With Megavoltage Computed Tomography-guided Helical Tomotherapy
- 1Department of Radiology, Toranomon Hospital, Tokyo, Japan
- 2Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Tokyo, Japan
- 3Department of Radiation Oncology, Toranomon Hospital, Tokyo, Japan
Abstract
Background/Aim: In helical tomotherapy (HT)-based total body irradiation (TBI), geometric accuracy is essential because intensity-modulated dose delivery relies on steep dose gradients. However, residual site-specific setup errors (SEs) after routine image guidance have not been fully characterized. This study quantified residual translational SEs after megavoltage computed tomography (MVCT)-guided global bony registration and derived landmark-specific planning target volume (PTV) and planning organ-at-risk volume (PRV) margins.
Patients and Methods: Twenty consecutive patients who underwent HT-based TBI as conditioning for allogeneic hematopoietic stem cell transplantation were retrospectively analyzed. A total dose of 12.0 Gy in four fractions was delivered using separate head-first and feet-first plans. After routine MVCT-guided registration, residual translational SEs were manually measured in the left-right, superior-inferior, and anterior-posterior directions at predefined anatomical landmarks: mandible, bilateral shoulders, pelvis, bilateral knees, bilateral heels, lung, liver, and bilateral kidneys. Systematic and random errors were calculated for each landmark, and PTV and PRV margins were estimated using modified margin recipes.
Results: Eighty fractions were analyzed. The mandible and lung showed high reproducibility, with residual SEs within 5.0 mm in all directions. In contrast, the shoulders showed the largest PTV-related uncertainty, with estimated PTV margins exceeding 10.0 mm in the superior-inferior and anterior-posterior directions. The liver and kidneys showed marked organ-related uncertainty, particularly in the superior-inferior direction; PRV margins reached 9.2 mm for the liver and up to 9.8 mm for the kidneys.
Conclusion: Residual SEs in MVCT-guided HT-based TBI were strongly site-dependent. Larger uncertainties in the shoulders, liver, and kidneys indicate that site-specific PTV and PRV margins should be considered rather than applying uniform margins across the whole body.
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BibTeX
@article{yamashita2026quantifying,
title = {{Quantifying Patient Setup Error in Total Body Irradiation With Megavoltage Computed Tomography-guided Helical Tomotherapy}},
author = {RYUTARO YAMASHITA and SHINGO OHIRA and YOHEI UTENA and KENTARO SUZUKI and KAZUKI SUZUKI and NAOYA KAMIYAMA and LICHT TOMINAGA and ISAO KURITA and MASAKATSU TANO and TAKUYO KOZUKA},
journal = {In Vivo},
year = {2026},
month = oct,
doi = {10.21873/invivo.14517},
url = {https://doi.org/10.21873/invivo.14517},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Quantifying Patient Setup Error in Total Body Irradiation With Megavoltage Computed Tomography-guided Helical Tomotherapy
AU - RYUTARO YAMASHITA
AU - SHINGO OHIRA
AU - YOHEI UTENA
AU - KENTARO SUZUKI
AU - KAZUKI SUZUKI
AU - NAOYA KAMIYAMA
AU - LICHT TOMINAGA
AU - ISAO KURITA
AU - MASAKATSU TANO
AU - TAKUYO KOZUKA
PY - 2026
DA - 2026/10/29
JO - In Vivo
DO - 10.21873/invivo.14517
UR - https://doi.org/10.21873/invivo.14517
AB - Background/Aim: In helical tomotherapy (HT)-based total body irradiation (TBI), geometric accuracy is essential because intensity-modulated dose delivery relies on steep dose gradients. However, residual site-specific setup errors (SEs) after routine image guidance have not been fully characterized. This study quantified residual translational SEs after megavoltage computed tomography (MVCT)-guided global bony registration and derived landmark-specific planning target volume (PTV) and planning organ-at-risk volume (PRV) margins. Patients and Methods: Twenty consecutive patients who underwent HT-based TBI as conditioning for allogeneic hematopoietic stem cell transplantation were retrospectively analyzed. A total dose of 12.0 Gy in four fractions was delivered using separate head-first and feet-first plans. After routine MVCT-guided registration, residual translational SEs were manually measured in the left-right, superior-inferior, and anterior-posterior directions at predefined anatomical landmarks: mandible, bilateral shoulders, pelvis, bilateral knees, bilateral heels, lung, liver, and bilateral kidneys. Systematic and random errors were calculated for each landmark, and PTV and PRV margins were estimated using modified margin recipes. Results: Eighty fractions were analyzed. The mandible and lung showed high reproducibility, with residual SEs within 5.0 mm in all directions. In contrast, the shoulders showed the largest PTV-related uncertainty, with estimated PTV margins exceeding 10.0 mm in the superior-inferior and anterior-posterior directions. The liver and kidneys showed marked organ-related uncertainty, particularly in the superior-inferior direction; PRV margins reached 9.2 mm for the liver and up to 9.8 mm for the kidneys. Conclusion: Residual SEs in MVCT-guided HT-based TBI were strongly site-dependent. Larger uncertainties in the shoulders, liver, and kidneys indicate that site-specific PTV and PRV margins should be considered rather than applying uniform margins across the whole body.
SN - 0258-851X
SN - 1791-7549
ER -