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Updated: Oct 19, 2026
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Published on: March 11, 2021
Independent Three-dimensional Dose Calculation from Log Files for Breast VMAT: A Measurement-free Quality Assurance
Rosa Angelica Petit Sevilla1,2, Oscar Abel Apaza Blanco2,3, Nayron Medeiros Soares1,2
1Department of Medical Physics, Instituto Zunino, Córdoba, Argentina.
Purpose:
The purpose of this study was to evaluate and validate a measurement-free patient-specific quality assurance (PSQA) approach for volumetric modulated arc therapy (VMAT) breast cancer treatments based on independent three-dimensional (3D) dose calculation from Digital Imaging and Communications in Medicine (DICOM) plans and linear accelerator log files.
Materials And Methods:
Seventy clinical breast VMAT plans (36 left-sided and 34 right-sided) were retrospectively analyzed. Independent 3D dose calculations were performed using RadCalc v7.3 based on the DICOM treatment plan (independent dose calculation [IDC] RTPlan) and on delivery log files acquired during the first treatment fraction (IDC LOGs). Results were compared with portal dosimetry (two-dimensional [2D]) and fluence-based analysis. Gamma passing rates (GPRs) were evaluated using 3%/2 mm and 2%/2 mm criteria under action (90%) and tolerance (95%) limits. Receiver operating characteristic (ROC) analysis was performed to evaluate the discriminatory capability. Sensitivity to delivery errors was investigated by introducing controlled multileaf collimator (MLC) shifts (0.5-2.0 mm) and collimator rotation errors (1°-3°).
Results:
All PSQA methods met the TG-218 action limit (GPR ≥ 90%) at 3%/2 mm. Under the stricter 2%/2 mm criterion, statistically significant differences among quality assurance methods were observed (P < 0.001). ROC analysis demonstrated superior discriminatory performance for 3D dose-based methods, with area under the curve values of 0.9 for both IDC RTPlan and IDC LOGs, compared with 0.7 for portal dosimetry and 0.5 for fluence-based analysis. Error sensitivity analysis showed that stringent gamma criteria (1%/2 mm and 1%/1 mm) improved detection of subtle MLC and collimator deviations, with log file-based 3D reconstruction outperforming 2D approaches.
Conclusions:
Independent 3D dose calculation is a reliable PSQA approach for breast VMAT, showing higher sensitivity than conventional 2D methods.
