Patient-Specific Dosimetric Validation of Pelvic IMRT and VMAT Plans Using a Custom-designed Female Pelvic Phantom and Arc-CHECK QA System

Introduction: To ensure the accuracy of advanced radiotherapy techniques in the therapy of female pelvic malignancies using radiotherapy, comprehensive quality assurance protocols and patient-specific dosimetry was performed using a custom-designed female pelvic (CDFP) phantom and Arc-CHECK.Material and Methods: Volumetric modulated arc therapy (VMAT) and Intensity modulated radiation therapy (IMRT) plans originally developed for patients with cervical cancer were transferred to the CDFP phantom and Arc-CHECK. The doses for patient-specific quality assurance (PSQA) of advanced techniques were calculated using different algorithms in treatment planning system (TPS). To acquire dose measurements, a 0.600 cc ion chamber, Sun Nuclear 125c (SNC125c) and a pinpoint 0.015 cc chamber were employed. The percentage deviation between the computed and administered dose was calculated. Results: Percentage discrepancies between planned and administered doses were analyzed. The maximum percentage deviation, mean ± standard deviation(SD) differences for 0.6 cc ion chamber and a pin-point 0.015 cc chamber were found to be -3.6%, -0.89% ± 1.59 and 3.51%, 1.10% ± 1.31 for the IMRT treatment technique and -3.32%, -0.84% ± 1.53 and 3.6%, 1.25% ± 1.34 for the VMAT treatment technique using AAA algorithms using 6MV beam for CDFP phantom respectively. The maximum of percentage deviation, mean ± SD differences for 0.6 cc ion chamber and a SNC125c chamber were found to be -3.40%, -0.273% ± 2.161 and 3.107%, -0.028% ± 2.046 for CDFP phantom and -2.72%, -0.35% ± 1.41 and 2.74%, 0.197% ± 1.50 for Arc-CHECK using VMAT treatment technique using 6MV beam and Monte Carlo algorithm respectively.Conclusion: The inherent properties of anthropomorphic phantoms like the CDFP, such an anatomical fidelity and tissue equivalence, make them extremely useful in the quality assurance radiotherapy-programs. Their application increases the accuracy of dosimetric validation and therefore, these phantoms are applicable in the use of high-accuracy treatment modalities such as IMRT and VMAT