Dosimetric and radiobiological comparison for quality assurance of IMRT and VMAT plans

Abstract

IntroductionThe gamma analysis used for quality assurance of a complex radiotherapy plan examines the dosimetric equivalence between planned and measured dose distributions within some tolerance. This study explores whether the dosimetric difference is correlated with any radiobiological difference between delivered and planned dose.Methods VMAT or IMRT plans optimized for 14 cancer patients were calculated and delivered to a QA device. Measured dose was compared against planned dose using 2‐D gamma analysis. Dose volume histograms (for various patient structures) obtained by interpolating measured data were compared against the planned ones using a 3‐D gamma analysis. Dose volume histograms were used in the Poisson model to calculate tumor control probability for the treatment targets and in the Sigmoid dose–response model to calculate normal tissue complication probability for the organs at risk.ResultsDifferences in measured and planned dosimetric data for the patient plans passing at ≥94.9% rate at 3%/3 mm criteria are not statistically significant. Average ± standard deviation tumor control probabilities based on measured and planned data are 65.8±4.0% and 67.8±4.1% for head and neck, and 71.9±2.7% and 73.3±3.1% for lung plans, respectively. The differences in tumor control probabilities obtained from measured and planned dose are statistically insignificant. However, the differences in normal tissue complication probabilities for larynx, lungs‐GTV, heart, and cord are statistically significant for the patient plans meeting ≥94.9% passing criterion at 3%/3 mm.ConclusionA ≥90% gamma passing criterion at 3%/3 mm cannot assure the radiobiological equivalence between planned and delivered dose. These results agree with the published literature demonstrating the inadequacy of the criterion for dosimetric QA and suggest for a tighter tolerance.

Incorporating biological modeling into patient‐specific plan verification

“…There are precedence available in the literature. In a 2017 study on patient‐specific QA of IMRT plans, 2D gamma analysis alone could not assure radiobiological equivalence between planned and delivered dose . The authors concluded that radiobiological analysis in addition to physical dose comparison may provide adequate patient‐specific QA of IMRT plans.…”

Dosimetric and radiobiological comparison in head-and-neck radiotherapy using JO-IMRT and 3D-CRT

“…The comparison of multi-types of radiotherapy plans using the radiobiological evaluation has been published in research ( Puzhakkal et al, 2016 ; Chow et al, 2020 , Rehman et al, 2018 , Kim et al, 2018 , Paudel et al, 2017 ). In 2016, Puzhakkal et al employed radiobiological techniques to confirm the treatment of 30 patients with head and neck and brain tumors as well as prostate cancers.…”

“…Limited statistically significant differences existed in either biological or physical dosage indices of the healthy nearby organs. Paudel et al examined IMRT and VMAT plans for quality assurance using the assessment method ( Paudel et al, 2017 ). They suggested that the radiobiological analysis should be considered for the assessment of complex radiotherapy plans.…”

Electronic Portal Imaging Device in Pre-Treatment Patient-Specific Quality Assurance of volumetric-modulated arc therapy delivery

“…9 The commercially available dosimetry systems, such as ionisation chamber, film and PSQA phantom, can be used for the PSQA procedure. 10 These dosimetry systems are integrated with software that analyses the outcome with TPS dose calculation in three-dimension is now widely used in the PSQA of VMAT. These dosimetry systems have been recommended by the AAPM Task Group 218.…”