No abstract

Purpose Stereotactic ablative body radiotherapy (SABR) in the liver, RTOG‐1112 guides the treatment modalities including the dose constraints for this technique but not the plan parameters. This study is not only analyzing the plan quality by utilizing the plan parameters and indexes but also compares treatment modalities from the protocol implementation. Method and material Twenty‐five patients treated in the period from February 2020 to September 2022 were recruited in this analysis. Two planners randomly selected the patients and modalities. The modalities employed were Volumetric‐Modulated Arc Therapy (VMAT) and Helical Tomotherapy (HT). Various parameters and indexes were used to access not only the plan quality but also to compare each modality. The parameters and indexes studied were the homogeneity index (HI), conformity index (CI), gradient distance (GD), and the dose received by the organs at risk. Result The data reveals that the mean volume of PTV is 60.8 ± 53.9 cc where these targets exhibit no significant difference between each modality. The HI shows a consistent value for both modalities. Between each modality, the CI value shows less deviation, but the HT shows slightly higher performance than VMAT. The value of GD is 1.5 ± 0.3 cm where the HT provides a shorter distance compared to VMAT as well. Conclusion The parameters and indexes should be utilized for the plan evaluation although in the guidelines this was not required. Various modalities were employed for treatment. Both can achieve the treatment criteria with slightly low performance of VMAT.

Aim: To propose a new matching method for the supraclavicular (SC) and tangential fields on three-dimensional radiotherapy (3DRT) for postmastectomy radiotherapy (PMRT). Methods: A method of matching coplanar field borders (CFB) between the tangential and SC fields was created in 3DRT. The collimator angle of the medial tangential field was calculated to coplanar the SC field. The proposed method performance was ultimately benchmarked using the half beam block (HBB) and traditional three-field monoisocenter (TTM) methods by dosimetric comparison. The decision score was then employed to clarify the performance among these methods. Results: The results show that the TTM method exhibited not only low doses on the organs at risk (OAR) but also on the matching fields. The CFB and HBB produced comparable results, but the ipsilateral lung yielded lesser amounts than the HBB. The decision score indicated a low performance level when using the TTM method, whereas the CBF method exhibited a slightly higher performance score than the HBB. Findings: The CFB exhibited good performance in terms of the dose on OARs and at the matching fields. This method offers a comparable level of performance to the HBB. Thus, the CFB offers an alternative method of significant interest in PMRT.