RT Journal Article SR Electronic T1 Dosimetric Comparison of Brain Sparing Between HyperArc and GammaKnife for Single to Triple Brain Metastases JF Anticancer Research JO Anticancer Res FD International Institute of Anticancer Research SP 1631 OP 1641 DO 10.21873/anticanres.17544 VO 45 IS 4 A1 UEDA, YOSHIHIRO A1 MORI, KANJI A1 OHIRA, SHINGO A1 TARUTANI, KAZUO A1 KANAYAMA, NAOYUKI A1 OKAMURA, AYAKO A1 KONISHI, KOJI YR 2025 UL http://ar.iiarjournals.org/content/45/4/1631.abstract AB Background/Aim: A novel linac-bases radiosurgery (SRS) system, HyperArc, applied to the non-coplanar volume-modulated arc therapy (VMAT) technique, was developed and released in clinical practice. The aim of the study was to evaluate the dosimetric performance of brain sparing in single-target to three-target cases, for two types of SRS systems: GammaKnife and HyperArc.Patients and Methods: A total of 83 patients treated with GammaKnife SRS (35 with single, 24 with double, and 24 with triple metastases) were retrospectively analyzed. Treatment plans were recalculated using HyperArc. Dosimetric parameters, including conformity index (CI), gradient index (GI), and brain volume receiving 2-20 Gy (V2-V20), were compared between the two systems.Results: No significant difference in D99 of the planning target volume (PTV) was observed between GammaKnife and HyperArc. HyperArc exhibited superior CI100, with values approaching 1.0. V4-V20 for the whole brain minus PTV were significantly lower for HyperArc than GammaKnife. In single-target cases, GI was significantly lower for HyperArc, while in triple-target cases, it was higher. V12 volumes for HyperArc were comparable to those for GammaKnife, even in cases with volumes <1.0 cm3.Conclusion: HyperArc demonstrated dosimetric performance comparable to or better than GammaKnife in brain sparing for single-to-triple metastases. These findings support HyperArc as an effective alternative for SRS planning.