Dosimetric quality and delivery efficiency of robotic radiosurgery for brain metastases: Comparison with C-arm linear accelerator based plans.

The incidence of brain metastases is increasing and various treatment modalities exist for brain metastases. The aim of this study was to investigate the dosimetric quality and delivery efficiency of robotic radiosurgery (CyberKnife) for multiple brain metastases compared with C-arm linear accelerator (linac) based plans. C-arm linac based plans included intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and non-coplanar VMAT with 1, 3 and 5 non-coplanar arcs, respectively (NC1, NC3 and NC5). For 20 patients, six plans with a prescription dose of 30 Gy in three fractions were generated. The gradient index (GI), conformity index (CI), maximum dose (Dmax ) of organs at risk (OARs), normal brain tissue volume (V3 Gy -V24 Gy ), monitor units (MUs) and beam on time (BT) were evaluated. The GI of CyberKnife plans (3.60 ± 0.70) was lower than IMRT (6.21 ± 2.26, P < 0.05), VMAT (6.04 ± 1.93, P < 0.05), NC1 (5.16 ± 1.71, P < 0.05), NC3 (5.02 ± 1.59, P < 0.05) and NC5 (5.03 ± 1.72, P < 0.05). The CI of the VMAT plans (both coplanar and non-coplanar) was larger than IMRT and CK plans. The Dmax for most OARs of the CyberKnife plan was lower than the C-arm linac based plans, although some differences were not statistically significant. The normal brain tissue volume of CyberKnife plan was lower than the C-arm linac based plans, and the normal brain tissue volume of non-coplanar VMAT plans was lower than IMRT and VMAT plans at high-moderate dose level. However, the MUs and BT of CyberKnife plans was more than C-arm linac based plans. CyberKnife plan was better than C-arm linac based plans in protecting normal brain tissue and OARs for patients with multiple brain metastases. C-arm linac based plan with non-coplanar arc provided better protection of normal brain tissue than coplanar plan. However, the BT of CyberKnife plan was longer than C-arm linac based plans.

Zhang S ，Yang R ，Wang X 《Journal of Applied Clinical Medical Physics》

Noncoplanar VMAT for Brain Metastases: A Plan Quality and Delivery Efficiency Comparison With Coplanar VMAT, IMRT, and CyberKnife.

Zhang S ，Yang R ，Shi C ，Li J ，Zhuang H ，Tian S ，Wang J ... -  《-》

Benchmarking techniques for stereotactic body radiotherapy for early-stage glottic laryngeal cancer: LINAC-based non-coplanar VMAT vs. Cyberknife planning.

Zhang Y ，Chiu T ，Dubas J ，Tian Z ，Lee P ，Gu X ，Yan Y ，Sher D ，Timmerman R ，Zhao B ... -  《Radiation Oncology》

Dosimetric comparison of robotic- and LINAC-based treatment of spine stereotactic body radiotherapy.

To determine which treatment technique and modality would offer better dosimetric results and be preferable for spinal stereotactic body therapy (SBRT) depending on the three different regions of the vertebrae. Linear accelerator (LINAC)- and CyberKnife (CK)-based treatment techniques were compared in terms of their dosimetric quality, treatment efficiency, and delivery accuracy. Thirty previously treated patients were included in this study. Intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques were used for LINAC-based treatment, whereas CK-based treatment plans were generated for two different collimator systems: fixed and multileaf collimator (MLC). The plans were compared based on spinal cord sparing, dose homogeneity, conformity index (CI), gradient index (GI), monitor unit (MU), and beam-on time. The percentage volumes of V2Gy, V5Gy (representing volume low of the dose spillage region), V10Gy, and V20Gy (representing the volume of the high-dose spillage region) of the healthy tissue were analyzed. The CI and GI of the VMAT plans were better than those of the IMRT plans. For spinal cord sparing, the VMAT and MLC-based CK (CK-MLC) techniques were superior. The percentage of low-dose spillage regions was the lowest for IMRT and fixed cone-based CK (CK-FIX) plans. The percentage of the high-dose spillage region was the lowest for the VMAT and CK-MLC plans. In terms of treatment efficiency, the VMAT and CK-MLC plans were superior to the IMRT and CK-FIX plans. The VMAT technique lowered the MU and beam-on time values. The plan delivery accuracy of the VMAT and CK-FIX plans was better than that of the IMRT plans. VMAT is the best option for LINAC-based spinal SBRT. For CK-based spinal SBRT, MLC-based plans are preferred. If the clinic has both treatment modalities and the patient can tolerate long treatment times, CK-MLC-based treatment should be chosen because of its superiority in sparing the spinal cord and sharp dose fall-off.

Acar H ，Yazici O ，Unal D 《-》

Dosimetric comparison of volumetric modulated arc therapy and linear accelerator-based radiosurgery for the treatment of one to four brain metastases.

The purpose of this study is to compare and evaluate volumetric modulated arc therapy (VMAT) and linear accelerator-based radiosurgery (Linac RS) for the treatment of one to four brain metastases. Radiotherapy plans for 10 patients with 1 to 4 brain metastases that were planned and treated using conventional Linac RS were replanned using a mono-isocentric VMAT technique using two to four arcs. The same doses, target volumes and organs at risk (OAR) were used in both plans. The plans were evaluated for target volume coverage, dose conformity, homogeneity and dose to OAR. For VMAT plans, 18/19 brain metastases met acceptable Radiation Therapy Oncology Group (RTOG) radiosurgery dose coverage, homogeneity and conformity criteria. There was no observed difference between the mean homogeneity indices for VMAT and Linac RS plans. VMAT plans had a lower mean RTOG conformity index compared with the Linac RS plans (1.10 ± 0.06 versus 2.06 ± 1.02). For the OAR, there was no difference in maximal doses to the brain stem, optic chiasm or optic nerves. The volume of normal brain receiving 12 Gy was lower in the VMAT plans (13.3 cm(3) versus 23.1 cm(3) ) compared with the Linac RS plans. The mean total number of monitor units (MUs) was 31.3% less in the VMAT plans (5231.2 MU versus 3593.5 MU). Mono-isocentric VMAT plans using two to four arcs meet RTOG radiosurgery quality criteria in patients with one to four brain metastases, with an improvement in conformity and 12-Gy normal brain volume when compared with patients treated with Linac RS at our institution.

Salkeld AL ，Unicomb K ，Hayden AJ ，Van Tilburg K ，Yau S ，Tiver K ... -  《-》