Efficacious patient-specific QA for Vertebra SBRT using a high-resolution detector array SRS MapCHECK: AAPM TG-218 analysis

Berk, K; Kron, T; Hardcastle, N; Yeo, AU

Author(s): Berk, K; Kron, T; Hardcastle, N; Yeo, AU;
Details: Publication Year 2024-06,Volume 25,Issue #6,Page e14276
Journal Title: Journal of Applied Clinical Medical Physics
Publication Type: Research article
Abstract: PURPOSE: Patient-specific quality assurance (PSQA) for vertebra stereotactic body radiation therapy (SBRT) presents challenges due to highly modulated small fields with high-dose gradients between the target and spinal cord. This study aims to explore the use of the SRS MapCHECK® (SRSMC) for vertebra SBRT PSQA. METHODS: Twenty vertebra SBRT treatment plans including prescriptions 20 Gy/1 fraction and 24 Gy/2 fractions were selected for each of Millennium (M)-Multileaf Collimator (MLC), and high-definition (HD)-MLC. All 40 plans were measured using Gafchromic EBT3 film (film) and SRSMC, using the StereoPHAN phantom. Plan complexity was assessed using modulation complexity score (MCS), edge metric (EM) (mm(-1)), modulation factor (MU/cGy), and average leaf pair opening (ALPO) (mm) and its correlation with gamma-pass rate was investigated. The high dose gradient between the target and the spinal cord was analyzed for film and SRSMC and compared against the treatment planning system (TPS). Applying the methodology proposed by AAPM TG-218, action and tolerance values specific to the SRSMC for vertebra SBRT were determined for β values ranging from 5 to 8. RESULTS: Film and SRSMC gamma-pass rates showed no correlation (p > 0.05). A moderate negative correlation (R = -0.57, p = 0.01) is present between EM and SRSMC 3%/1 mm gamma-pass rate for HD-MLC plans. Both film and SRSMC accurately measured high dose gradients between the target and the spinal cord (R(2) > 0.86, p ≤ 0.05). Notably, dose-gradient of HD-MLC plans is 22% steeper and has a smaller standard deviation to M-MLC plans (p ≤ 0.05). Applying TG-218, the film tolerance limit was 96% with action limit 95% for 5%/1 mm (β = 6) and for the SRSMC tolerance limit was 97% with an action limit of 96% for 4%/1 mm (β = 6). CONCLUSION: Our findings suggest that universal TG-218 limits may not be suitable for vertebra SBRT PSQA. This study demonstrates that SRSMC is a viable tool for vertebra SBRT PSQA, supported by TG-218 implementation of process-based tolerance and action limits.
Publisher: Wiley
Keywords: Humans; *Radiosurgery/methods; *Radiotherapy Planning, Computer-Assisted/methods; *Radiotherapy Dosage; *Radiotherapy, Intensity-Modulated/methods; *Quality Assurance, Health Care/standards; *Organs at Risk/radiation effects; *Phantoms, Imaging; Spinal Neoplasms/surgery/radiotherapy; SRS MapCHECK; Tg‐218; patient‐specific quality assurance (PSQA); vertebra SBRT
Department(s): Physical Sciences
Publisher's Version: https://doi.org/10.1002/acm2.14276
Open Access at Publisher's Site: https://doi.org/10.1002/acm2.14276
Terms of Use/Rights Notice: Refer to copyright notice on published article.

Creation Date: 2024-07-30 06:33:43

Last Modified: 2024-07-30 06:34:36