目的:避免海马全脑放疗(HA-WBRT)计划可能会带来挑战。本研究考察了头部倾斜角度对目标和危险器官(OAR)剂量学特征的影响,旨在确定使用断层疗法(TOMO)产生最佳剂量测定结果的最佳倾斜角。
方法:8例脑转移瘤患者接受了5个倾斜角度的CT扫描:[0°,10°),[10°,20°),[20°,30°),[30°,40°),和[40°,45°].使用TOMO和体积调节电弧疗法(VMAT)生成治疗计划。剂量学参数,包括合格指数(CI),同质性指数(HI),D2cc,D98%,和PTV的Dmean,以及Dmax,分析了OAR的Dmean值。此外,比较了TOMO和VMAT计划的剂量学参数.最后,评估了TOMO计划的交付效率。
结果:对于PTV,[40°,45°]倾斜角显示出明显更好的一致性,同质性,较低的D2cc,和较低的Dmean为PTV。关于OAR,[40°,45°]头部倾斜角度显示海马区Dmax和Dmean明显降低,眼睛,视神经交叉,和视神经.[40°,45°]倾斜角度也显示脑干和耳蜗的Dmax明显降低,以及镜头的较低Dmean。在[40°,45°]HA-WBRT的倾斜角,对于PTV,TOMO表现出优于VMAT的性能。TOMO的脑干Dmax降低,耳蜗,视神经,和视神经交叉,以及海马体的较低Dmean。此外,分娩时间与矢状平面上的PTV投影长度之间存在显着相关性。
结论:使用倾斜角度范围为[40°,45°]表现出优异的PTV一致性和均匀性,以及增强的OAR保留。此外,对于相同角度范围内的PTV和大多数OAR,它比VMAT具有剂量学优势。
OBJECTIVE: Hippocampal-avoidance whole-brain radiotherapy (HA-WBRT) planning can present challenges. This study examines the influence of head tilt angles on the dosimetric characteristics of target and organs at risk (OARs), aiming to identify the optimal tilt angle that yields optimal dosimetric outcomes using tomotherapy (TOMO).
METHODS: Eight patients diagnosed with brain metastases underwent CT scans at five tilt angles: [0°, 10°), [10°, 20°), [20°, 30°), [30°, 40°), and [40°, 45°]. Treatment plans were generated using TOMO and volumetric modulated arc therapy (VMAT). Dosimetric parameters including conformity index (CI), homogeneity index (HI), D2cc, D98%, and Dmean of PTV, as well as Dmax, and Dmean of OARs were analyzed. Furthermore, a comparison was made between the dosimetric parameters of TOMO and VMAT plans. Finally, delivery efficiency of TOMO plans were assessed.
RESULTS: For the PTV, [40°, 45°] tilt angle demonstrated significantly better conformity, homogeneity, lower D2cc, and lower Dmean for the PTV. Regarding the OARs, the [40°, 45°] head tilt angle demonstrated significantly lower Dmax and Dmean in hippocampus, eyes, optic chiasm, and optic nerves. The [40°, 45°] tilt angle also showed significantly lower Dmax for brainstem and cochleas, as well as a lower Dmean for lens. In the [40°,45°] tilt angle for HA-WBRT, TOMO showed superior performance over VMAT for the PTV. TOMO achieved lower Dmax for brainstem, cochleas, optic nerves, and optic chiasm, as well as a lower Dmean for hippocampus. Furthermore, a significant correlation was found between delivery time and the PTV projection length in the sagittal plane.
CONCLUSIONS: The TOMO plan utilizing a tilt angle range of [40°, 45°] demonstrated superior PTV conformity and uniformity, along with enhanced OARs sparing. Furthermore, it exhibited a dosimetric advantage over VMAT for PTV and most OARs at the same angle range.