背景:放疗过程中患者位置的准确性和精确性对肿瘤局部控制和治疗相关副作用有重大影响,存在探索有效定位解决方案的需求,尤其是在图像识别与匹配取得巨大进步的时代。
目的:提出了基于浅表血管的近红外辅助患者位置识别和实时监测系统(VIPS),以开发一种自动,独立于操作员和无皮肤标记的成像系统,以改善患者设置和动态运动监测。
方法:VIPS包括两个组件,成像模块和图像对齐软件。使用模拟血管模型,在成像质量方面评估了具有各种波长和推注(假皮肤)的多个NIR源,以确定最佳光源和浅表脂肪组织厚度的上限.然后,使用3D体模和注册临床试验的临床病例,参考CBCT或激光设置系统进行VIPS的性能。比较了VIPS和激光系统的位置位移,以及VIPS设置程序的系统误差和随机误差。
结果:组合波长为760nm+940nm(S760+940nm)的NIR光源在多个测试光源中提供了最佳性能。超过5mm的团块(浅表脂肪层)厚度可能显著损害下面的血管的NIR检测。在幻影研究中,根据VIPS指导的平移位置位移在参考CBCT的亚毫米水平内,指示高设置精度。临床试验表明,VIPS原型能够有效检测并控制患者在平移和旋转方向上的位置位移在可接受的范围内,这是不劣于传统的激光/皮肤标记系统。
结论:这项概念验证研究验证了VIPS在指导放疗设置方面的可行性和可靠性。然而,限制和技术挑战应在进一步临床评估之前解决,包括等中心对齐,潜在的近红外图像失真和浅表组织对血管识别的影响。
BACKGROUND: The accuracy and precision of patient position in radiotherapy process have dramatic impacts on the tumor local control and therapy-related side effects, and there exist demands to explore effective positioning solutions, particularly in the era with great progress in imaging recognition and matching.
OBJECTIVE: Superficial vessel-based near infrared-assisted patient position recognition and real-time monitoring system (VIPS) was proposed to develop an automated, operator-independent and skin marker-free imaging system to improve patient setup and intrafractional motion monitoring.
METHODS: VIPS includes two components, the imaging module and the image alignment software. Using a simulated blood vessel model, multiple NIR sources with various wavelength and bolus (pseudo-skin) were evaluated in terms of imaging quality to determine the optimal light source and the upper limit of superficial fatty tissue thickness. Then the performance of VIPS with reference to either CBCT or laser setup system was conducted using 3D phantom and clinical cases enrolled into the registered clinical
trial. The position displacement from VIPS and laser system was compared, as well as the systematic and random errors of VIPS setup procedure.
RESULTS: The NIR light source with the combined wavelengths of 760 nm + 940 nm (S760+940 nm ) provided the best performance among multiple tested light sources. The bolus (superficial fatty layer) thickness over 5 mm could dramatically compromise the NIR detection of vessels beneath. In the phantom
study, the translational positional displacements according to VIPS guidance were within the submillimeter level with reference to CBCT, indicative of high setup accuracy. The clinical
trial showed the prototype VIPS could effectively detect and control position displacement of patients in translational and rotational directions within an acceptable range, which was non-inferior to conventional laser/skin marker system.
CONCLUSIONS: This proof-of-concept
study validated the feasibility and reliability of VIPS in guiding radiotherapy setup. However, limitations and technical challenges should be resolved prior to further clinical evaluation, including isocenter alignment, potential NIR image distortion and the impact of the superficial tissues on the recognition of vessels.