Room: Exhibit Hall
Purpose: The purpose of the present study is to ascertain whether the dose distribution delivered by dynamic conformal arc therapy (DCAT) exhibits as good of an agreement with the planned dose distribution as the volumetric modulated arc therapy (VMAT) delivery and if it can be used more efficiently, specifically for SBRT lung and liver treatments.
Methods: Nineteen (n=19) patients previously treated for lung and liver lesions with SBRT were chosen for this study. All patients' organs at risk and targets were contoured by a single physician. All patient plans were optimized using the ELEKTA Monaco treatment planning system for a VersaHD 6MV flattening filter free (FFF) photon beam. Two plans were optimized for each patient, one using VMAT and one using DCAT. For each plan two arcs of 225o arc span were used during optimization.
Results: Overall, all plans have achieved the planning objectives that were set prior to optimization. The MU for the DCAT plans were reduced by an average of 2.5 times when compared against the VMAT plans. The target coverage was more favorable for the VMAT plans (average values of PTVr=1.3 and DCAT PTVr=1.4 respectively), but this was not shown to be statistically significant. Larger differences between VMAT and DCAT plan quality metrics occurred when OARs were very close to or overlapped with the PTV. In such instances, the DCAT plans were inferior to the respective VMAT plans in terms of quality. For targets far from OARs, the DCAT plans showed improved PTV coverage and OAR sparing than the respective VMAT plans.
Conclusion: DCAT delivery for lung and liver SBRT treatments is a viable alternative to VMAT plans. While maintaining plan quality, DCAT deliveries are on average 2.5 times faster. Higher delivery accuracy was measured for DCAT plans using a multidimensional array.
Funding Support, Disclosures, and Conflict of Interest: Research supported by ELEKTA
Lung, Dosimetry, Radiation Therapy