Hazelwood Kate, McCarthy Shane, Misa Josh, Castelvetere David, St Clair William, Pokhrel Damodar
Medical Physics Graduate Program, Department of Radiation Medicine, University of Kentucky, Lexington, Kentucky, USA.
Rhodes College, Physics, Biochemistry and Molecular Biology, Memphis, Tennessee, USA.
J Appl Clin Med Phys. 2025 Jun;26(6):e70105. doi: 10.1002/acm2.70105. Epub 2025 Apr 9.
An evaluation of the accuracy, safety, and efficiency of the Halcyon ring delivery system (RDS) for stereotactic radiosurgery (SRS) treatment to relatively small (1-3 cm) brain lesions.
After completing the extensive in-house quality assurance checks including Winston-Lutz test and independent dose verification via MD Anderson IROC SRS head phantom irradiation on Halcyon, fifteen brain SRS patients previously treated with a single dose of 20 Gy on TrueBeam (6MV-FFF) with HyperArc geometry were retrospectively replanned on Halcyon (6MV-FFF). Plan quality metrics including conformity index (CI), gradient index (GI), gradient distance (GD), PTV coverage, gross tumor volume (GTV) dose, heterogeneity index (HI), and doses to organs-at-risk (OAR) including normal brain dose were evaluated. Patient-specific quality assurance (PSQA) and independent dose verification via in-house Monte Carlo (MC) 2nd checks were performed.
The Halcyon was able to provide highly conformal brain SRS plans. When compared to TrueBeam, CI, planning target volume (PTV) coverage, GTV dose (mean and minimum), HI, and doses to brainstem, optic pathway, and cochlea were statistically insignificant. Statistically significant increases in GI (3.76 vs. 3.25, p < 0.001), GD (0.56 cm vs. 0.48 cm, p = 0.001), and V (5.5 cc vs. 4.6 cc, p = 0.014), on average using Halcyon versus TrueBeam was found, albeit clinically acceptable values for the majority of brain SRS cases. Halcyon plans provided statistically insignificant maximum dose to most adjacent OARs, though there was a statistically significant decrease in the maximum dose to the spinal cord (0.1 Gy vs. 0.4 Gy, p = 0.009). Halcyon beam-on time increases by a factor of ∼2 (p < 0.001). However, the faster patient setup on Halcyon results in a comparable estimated overall treatment time for both platforms. Plan deliverability and accuracy was ensured with PSQA (> 95% pass rate for 2%/2 mm clinical gamma criteria) results and MC 2nd check agreement within ± 5.0%.
Halcyon brain SRS plans provided a similar plan quality compared to HyperArc plans, although it demonstrated an inferior intermediate dose fall off thus slightly higher V. This study suggests that Halcyon provides acceptable treatment for solitary relatively small brain lesions of 1-3 cm in diameter. Treatment of select patients on Halcyon will be started at our clinic and it is recommended that other clinics complete an end-to-end test, validate, and implement Halcyon SRS treatments at their practices, especially community cancer centers to provide high-quality service to an underserved patient cohort.
评估Halcyon环形放射治疗系统（RDS）用于立体定向放射外科（SRS）治疗相对较小（1 - 3厘米）脑病变的准确性、安全性和效率。
在完成包括温斯顿-卢茨测试和通过MD安德森IROC SRS头部体模对Halcyon进行独立剂量验证等广泛的内部质量保证检查后，对15例先前在TrueBeam（6MV-FFF）上采用HyperArc几何形状单次给予20 Gy剂量治疗的脑SRS患者进行回顾性重新计划，在Halcyon（6MV-FFF）上进行。评估计划质量指标，包括适形指数（CI）、梯度指数（GI）、梯度距离（GD）、计划靶体积（PTV）覆盖率、大体肿瘤体积（GTV）剂量、异质性指数（HI）以及对危及器官（OAR）的剂量，包括正常脑剂量。进行患者特异性质量保证（PSQA）并通过内部蒙特卡罗（MC）二次检查进行独立剂量验证。
Halcyon能够提供高度适形的脑SRS计划。与TrueBeam相比，CI、PTV覆盖率、GTV剂量（平均值和最小值）、HI以及对脑干、视路和耳蜗的剂量在统计学上无显著差异。发现平均而言，使用Halcyon与TrueBeam相比，GI有统计学显著增加（3.76对3.25，p < 0.001），GD（0.56厘米对0.48厘米，p = 0.001）以及V（5.5立方厘米对4.6立方厘米，p = 0.014），尽管对于大多数脑SRS病例这些值在临床上是可接受的。Halcyon计划对大多数相邻OAR的最大剂量在统计学上无显著差异，不过对脊髓的最大剂量有统计学显著降低（0.1 Gy对0.4 Gy，p = 0.009）。Halcyon的束流开启时间增加了约2倍（p < 0.001）。然而，Halcyon上更快的患者摆位导致两个平台的估计总体治疗时间相当。PSQA（对于2%/2毫米临床伽马标准通过率> 95%）结果和MC二次检查在±5.0%范围内的一致性确保了计划的可交付性和准确性。
与HyperArc计划相比，Halcyon脑SRS计划提供了相似的计划质量，尽管它显示出中等剂量下降较差，因此V略高。本研究表明，Halcyon为直径1 - 3厘米的孤立相对较小脑病变提供了可接受的治疗。我们诊所将开始对选定患者使用Halcyon进行治疗，建议其他诊所完成端到端测试、验证并在其实践中实施Halcyon SRS治疗，特别是社区癌症中心，以便为服务不足的患者群体提供高质量服务。
