PurposeThe HyperArc VMAT (HA-VMAT) planning approach was newly developed to fulfill the demands of dose delivery for brain metastases stereotactic radiosurgery. We compared the dosimetric parameters of the HA-VMAT plan with those of the conventional VMAT (C-VMAT).Material and methodsFor 23 patients (1–4 brain metastases), C-VMAT and HA-VMAT plans with a prescription dose of 20–24 Gy were retrospectively generated, and dosimetric parameters for PTV (homogeneity index, HI; conformity index, CI; gradient index, GI) and brain tissue (V2Gy-V16Gy) were evaluated. Subsequently, the physical characteristics (modulation complexity score for VMAT, MCSV; Monitor unit, MU) of both treatment approaches were compared.ResultsHA-VMAT provided higher HI (1.41 ± 0.07 vs. 1.24 ± 0.07, p < 0.01), CI (0.93 ± 0.02 vs. 0.90 ± 0.05, p = 0.01) and lower GI (3.06 ± 0.42 vs. 3.91 ± 0.55, p < 0.01) values. Moderate-to-low dose spreads (V4Gy-V16Gy) were significantly reduced (p < 0.01) in the HA-VMAT plan over that of C-VMAT. HA-VMAT plans resulted in more complex MLC patterns (lower MCSV, p < 0.01) and higher MU (p < 0.01).ConclusionsHA-VMAT plans provided significantly higher conformity and rapid dose falloff with respect to the C-VMAT plans.

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& teruki teshima 1 the prognosis of hepatocellular carcinoma (Hcc) with portal vein tumour thrombus (pVtt) is poor. We conducted a prospective study to evaluate the efficacy and safety of tri-modality therapy, including preoperative stereotactic body radiotherapy (SBRt) and surgery, followed by hepatic arterial infusion chemotherapy (HAic) in Hcc patients with pVtt. in this report, we investigated the pathology of the irradiated PVTT specimen in resected cases and SBRT-related acute toxicity. A total of 8 HCC patients with PVTT received preoperative SBRT targeting the PVTT at a dose of 48 Gy in 4 fractions at our institute from 2012 to 2016. Of the eight patients, six underwent surgery, while the remaining two did not because of disease progression. At the pathological examination, all patients' irradiated pVtt specimens showed necrotic tissue, and three of six patients showed complete pathological response. Two patients showed 30% necrosis with high degeneration and one patient, with 30% necrosis without degeneration, was the only recurrent case found during the follow-up period (median: 22.5, range: 5.9-49.6 months). No SBRT-related acute toxicity worse than grade 2 was observed from SBRT to surgery. In conclusion, the preoperative SBRT for HCC was pathologically effective and the acute toxicities were tolerable.

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