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Influence of dose calculation algorithms on the helical diode array using volumetric-modulated arc therapy for small
Tomohiro Ono1, Hideaki Hirashima1, Takanori Adachi1
1Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Journal of Applied Clinical Medical Physics
|February 16, 2024
Summary
Dose calculation algorithms significantly impact patient-specific quality assurance for small targets. Acuros XB (AXB) showed lower accuracy for narrow beams, affecting gamma passing rates in VMAT small target measurements.
Area of Science:
- Medical Physics
- Radiation Oncology
- Dosimetry
Background:
- Patient-specific quality assurance (PSQA) is crucial for small targets in radiation therapy.
- Dose calculation algorithms (DCAs) can influence dose resolution and accuracy in PSQA.
- Evaluating different DCAs is essential for reliable small target treatment verification.
Purpose of the Study:
- To assess the impact of Acuros XB (AXB), anisotropic analytical algorithm (AAA), photon Monte Carlo (pMC), and collapsed cone (CC) dose calculation algorithms.
- To evaluate these algorithms on a helical diode array using volumetric-modulated arc therapy (VMAT) for small targets.
- To determine the influence of DCA characteristics on gamma passing rates (GPRs) for small targets.
Main Methods:
- Measurements were performed using ArcCHECK detectors at a depth of 2.9 cm.
- Rectangular fields (2x100 to 100x100 mm²) and 20 clinical VMAT plans (brain metastases, spine) were analyzed.
- Gamma passing rates (3%/2 mm) were calculated for AXB, AAA, pMC, and CC on the TrueBeam STx system.
Main Results:
- Acuros XB (AXB) exhibited GPRs <50% for narrow beams (2x100, 5x100 mm²) due to coarser dose resolution.
- For larger fields (>10x100 mm²), GPRs were >88.1% and comparable across all evaluated DCAs.
- For clinical VMAT plans, GPRs were 79.1% (AXB), 93.2% (AAA), 94.9% (pMC), and 94.5% (CC).
Conclusions:
- Dose distribution behavior varies among DCAs for small targets on helical diode arrays.
- Acuros XB's coarser dose resolution can lead to lower GPRs in ArcCHECK measurements for VMAT small targets.
- Accurate dose calculation is vital for reliable VMAT quality assurance, especially for small and complex targets.
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