End-to-End patient-specific VMAT quality assurance for common Head-and-Neck cancers using RANDO anthropomorphic phantom with OSLD

Abstract

Patient-Specific Quality Assurance is usually performed using phantoms made of homogeneous materials with regular shapes and small sizes, which does not simulate real world considerations. This work aims to establish and implement an efficient end-to-end quality assurance protocol for Volumetric Modulated Arc Therapy treatment plans for Head-and-Neck (H&N) cancers using adult RANDO anthropomorphic phantom to assess the overall treatment chain uncertainty and accuracy. Four VMAT treatment plans of H&N cancers (Brain metastases, Parotid glands, Nasopharynx, and Larynx) were selected based on their clinical incidence frequency. The phantom passed through the same treatment process as patient to simulate a real world scenario. These plans were applied to the phantom as QA-plans. The mean dose discrepancies describing the entire plan deliverability and acceptability were 0.76% $\pm$ 2.22%, 0.68% $\pm$ 4.51%, 1.56% $\pm$ 2.85%, and 2.04% $\pm$ 3.53% for Brain metastases, parotid glands, nasopharyngeal, and laryngeal cancers respectively. Plans standard deviations ($S{D}_{TPS-OSLD}$) tend to increase with mean differences $\overline{Max-min}$ because of dose heterogeneity at the measurement positions. Over all plans, a lower difference of about 0.72% was shown between the highest and the lowest in-field standard deviation $S{D}_{in}$ (%). Out-of-field standard deviations $S{D}_{out}$ (%) indicated a highest dose discrepancy due to organ at risk to be spared. VMAT treatment plans for Head-and-Neck cancers are extremely complex processes, involving many uncertainties that could affect the desired plan administration accuracy. Therefore, it is essential to implement such an end-to-end test, in order to verify system ability to reach therapeutic goals and spare organs at risk, taking into account all the related uncertainties.