Medical Physics Graduate Program, Department of Radiation Medicine, University of Kentucky, Lexington, Kentucky, USA.
J Appl Clin Med Phys. 2022 May;23(5):e13555. doi: 10.1002/acm2.13555. Epub 2022 Feb 7.
To demonstrate the plan quality and delivery efficiency of volumetric-modulated arc therapy (VMAT) with the Halcyon Linac ring delivery system (RDS) in the treatment of single-isocenter/two-lesion lung stereotactic body radiation therapy (SBRT).
MATERIALS/METHODS: Sixteen previously treated non-coplanar VMAT single-isocenter/two-lesion lung SBRT plans delivered with SBRT-dedicated C-arm TrueBeam Linac were selected. Prescribed dose was 50 Gy to each lesion over five fractions with treatment delivery every other day and AcurosXB algorithm as the final dose calculation algorithm. TrueBeam single-isocenter plans were reoptimized for Halcyon Linac with coplanar geometry. Both TrueBeam and Halcyon plans were normalized for identical combined target coverage and evaluated. Conformity indices (CIs), heterogeneity index (HI), gradient index (GI), gradient distance (GD), and D were compared. The normal lung V5Gy, V10Gy, V20Gy, mean lung dose (MLD), and dose to organs at risk (OAR) were evaluated. Treatment delivery parameters, including beam-on time, were recorded.
Halcyon plans were statistically similar to clinically delivered TrueBeam plans. No statistical differences in target conformity, dose heterogeneity, or intermediate-dose spillage were observed (all, p > 0.05). Halcyon plans, on average, demonstrated statistically insignificant reduced maximum dose to most adjacent OAR and normal lung. However, Halcyon yielded statistically significant lower maximal dose to the ribs (p = 0.041) and heart (p = 0.026), dose to 1 cc of ribs (p = 0.035) and dose to 5 cc of esophagus (p = 0.043). Plan complexity slightly increased as seen in the average increase of total monitor units, modulation factor, and beam-on time by 480, 0.48, and 2.78 min, respectively. However, the estimated overall treatment time was reduced by 2.22 min, on average. Mean dose delivery accuracy of clinical TrueBeam plans and the corresponding Halcyon plans was 98.9 ± 0.85% (range: 98.1%-100%) and 98.45 ± 0.99% (range: 97.9%-100%), respectively, demonstrating similar treatment delivery accuracy.
SBRT treatment of synchronous lung lesions via single-isocenter VMAT on Halcyon RDS is feasible and dosimetrically equivalent to clinically delivered TrueBeam plans. Halcyon provides excellent plan quality and shorter overall treatment time that may improve patient compliance, reduce intrafraction movement, improve clinic efficiency, and potentially offering lung SBRT treatments for underserved patients on a Halcyon only clinic.
展示 Halcyon 直线加速器环输送系统（RDS）在治疗单中心/双病灶肺癌立体定向体部放射治疗（SBRT）中的容积调制弧形治疗（VMAT）的计划质量和交付效率。
材料/方法：选择了 16 例先前接受过非共面 VMAT 单中心/双病灶肺癌 SBRT 治疗的计划，这些计划均采用 SBRT 专用 C 臂 TrueBeam 直线加速器进行治疗。每个病灶的处方剂量为 50Gy，分 5 次进行，隔日进行治疗，最终剂量计算算法为 AcurosXB 算法。对 TrueBeam 单中心计划进行了优化，以适应 Halcyon 直线加速器的共面几何形状。对 TrueBeam 和 Halcyon 计划进行归一化，以获得相同的综合靶区覆盖率，并进行评估。比较了适形指数（CI）、不均匀性指数（HI）、梯度指数（GI）、梯度距离（GD）和 D。评估了正常肺的 V5Gy、V10Gy、V20Gy、平均肺剂量（MLD）和危及器官（OAR）的剂量。记录了治疗输送参数，包括射束开启时间。
Halcyon 计划在统计学上与临床交付的 TrueBeam 计划相似。在靶区适形性、剂量不均匀性或中等剂量外溢方面没有观察到统计学差异（均，p＞0.05）。平均而言，Halcyon 计划对大多数相邻 OAR 和正常肺的最大剂量表现出统计学上无显著降低。然而，Halcyon 对肋骨（p=0.041）和心脏（p=0.026）的最大剂量、肋骨 1cc 剂量（p=0.035）和食管 5cc 剂量（p=0.043）的剂量显著降低。计划复杂性略有增加，总监测单位、调制因子和射束开启时间平均增加 480、0.48 和 2.78 分钟。然而，平均治疗时间减少了 2.22 分钟。临床 TrueBeam 计划和相应的 Halcyon 计划的平均剂量输送准确性分别为 98.9±0.85%（范围：98.1%-100%）和 98.45±0.99%（范围：97.9%-100%），表明治疗输送准确性相似。
通过 Halcyon RDS 对单中心同步肺病灶进行 SBRT 治疗是可行的，在剂量学上与临床交付的 TrueBeam 计划相当。Halcyon 提供了出色的计划质量和更短的整体治疗时间，这可能会提高患者的依从性，减少分次内运动，提高临床效率，并有可能为仅接受 Halcyon 治疗的服务不足的患者提供肺癌 SBRT 治疗。
