Dosimetric comparison and delivery accuracy between DCAT and VMAT for stereotactic body radiotherapy using the deep inspiration breath-hold technique in liver cancer

Abstract Purpose: To compare plan quality and delivery accuracy between Volumetric Modulated Arc Therapy (VMAT) and 3-dimensional Dynamic Conformal Arc Therapy (DCAT) for liver stereotactic body radiotherapy (SBRT) using deep inspiration breath-hold (DIBH). Methods: Fifteen SBRT liver cancer cases of VMAT were reconducted using DCAT. To minimize planning subjectivity, DCAT plan was created as the originated VMAT geometry such as prescription dose, arc ranges, and collimator angles. Plan quality was analyzed using dosimetric parameters of target, organ-at-risk (OARs) and intermediate-dose spillage, including the plan efficacy such as MU, and beam-on time. Delivery accuracy was assessed using Gamma passing rate (GPR) under static and dynamic motion with 2D-array detectors and a gradient 1D motion platform. Results: VMAT showed significantly superior values in some dosimetric parameters of target and intermediate-dose spillage compared to DCAT, whereas the conformity index showed no significant difference. In contrast, the beam-on time and MU of DCAT were significantly lower than VMAT. Additionally, all considered OARs showed no significant difference between the two techniques. The GPR of DCAT was significantly higher than that of VMAT in both static and dynamic motion. Interestingly, DCAT showed no significant difference of GPR value between these two motions, whereas the VMAT revealed a significant decrease when transitioning to dynamic motion. Conclusion: VMAT showed better plan quality than DCAT in liver SBRT. However, both techniques met the treatment criteria. Moreover, DCAT provided shorter treatment time and higher delivery accuracy, supporting DCAT as a practical selective alternative for liver SBRT in appropriately selected DIBH cases.