Quantitative verification of treatment delivery accuracy utilizing deep inspiration breath hold (DIBH) for left-sided breast irradiation

Abstract

Abstract Purpose: To assess the treatment delivery accuracy of left-sided breast irradiation using the deep inspiration breath hold (DIBH) technique via Gamma passing rate (GPR) analysis. Methods: Thirteen patients with left-sided breast cancer who had previously undergone volumetric modulated arc therapy (VMAT) were retrospectively selected. Each case was replanned using three-dimensional conformal radiotherapy (3D-CRT). The delivery system utilized a 1D vertical moving platform driven by DIBH respiratory cycles, with radiation delivery governed by surface-guided radiotherapy (SGRT) using a 5 mm gating window. Radiation doses for both VMAT and 3D-CRT plans were measured using a cross-array detector. Delivery accuracy was evaluated in both static and dynamic motion using GPR at 3%/2mm and 3%/3mm criteria. Statistical significance was assessed at a 95% confidence level. Results: Under static conditions, VMAT plans yielded GPR of 97.20 ± 1.61% and 99.13 ± 0.48% for 3%/2mm and 3%/3mm criteria, respectively. These values were significantly higher than those observed during dynamic motion (96.55 ± 2.19%; p = 0.004 and 98.82 ± 0.75%; p = 0.012). Conversely, 3D-CRT showed no significant differences between static (96.18 ± 5.55 and 97.56 ± 4.32) and dynamic motion (95.93 ± 5.17 and 97.35 ± 4.76 for Gamma criterion, respectively) across either criterion. Furthermore, no significant differences in GPR were found when comparing VMAT and 3D-CRT techniques against each other under either motion condition. Conclusion: VMAT plans demonstrated significant sensitivity to dynamic motion, as evidenced by the decrease in GPR. Conversely, 3D-CRT maintains delivery accuracy regardless of motion conditions. These findings suggest that for treatments involving significant respiratory motion, the high-precision benefits of VMAT must be carefully balanced against its motion-induced delivery inaccuracies.