Independent Three-dimensional Dose Calculation from Log Files for Breast VMAT: A Measurement-free Quality Assurance Approach
Rosa Angelica Petit Sevilla, Oscar Abel Apaza Blanco, Nayron Medeiros Soares, Maximiliano Musso, Ezequiel Agustín Cabrera Lacey, Luis C Bohorquez, Lucy Wolfsberger, Maria José Almada, Carlos Daniel VenenciaAbstract
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 (
Conclusions:
Independent 3D dose calculation is a reliable PSQA approach for breast VMAT, showing higher sensitivity than conventional 2D methods.