Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA.
Med Phys. 2019 May;46(5):1995-2005. doi: 10.1002/mp.13507. Epub 2019 Apr 22.
Lung motion phantoms used to validate radiotherapy motion management strategies have fairly simplistic designs that do not adequately capture complex phenomena observed in human respiration such as external and internal deformation, variable hysteresis and variable correlation between different parts of the thoracic anatomy. These limitations make reliable evaluation of sophisticated motion management techniques quite challenging. In this work, we present the design and implementation of a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers.
An in-house-designed lung module, made from natural latex foam was inserted inside the outer shell of a commercially available lung phantom (RSD, Long Beach, CA, USA). Radiopaque markers were placed on the external surface and embedded into the lung module. Two independently programmable high-precision linear motion actuators were used to generate primarily anterior-posterior (AP) and primarily superior-inferior (SI) motion in a reproducible fashion in order to enable (a) variable correlation between the displacement of interior volume and the exterior surface, (b) independent changes in the amplitude of the AP and SI motions, and (c) variable hysteresis. The ability of the phantom to produce complex and variable motion accurately and reproducibly was evaluated by programming the two actuators with mathematical and patient-recorded lung tumor motion traces, and recording the trajectories of various markers using kV fluoroscopy. As an example application, the phantom was used to evaluate the performance of lung motion models constructed from kV fluoroscopy and 4DCT images.
The phantom exhibited a high degree of reproducibility and marker motion ranges were reproducible to within 0.5 mm. Variable correlation was observed between the displacements of internal-internal and internal-external markers. The SI and AP components of motion of a specific marker had a correlation parameter that varied from -11 to 17. Monitoring a region of interest on the phantom's surface to estimate internal marker motion led to considerably lower uncertainties than when a single point was monitored.
We successfully designed and implemented a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers.
用于验证放疗运动管理策略的肺部运动体模设计相当简单，无法充分捕捉到人体呼吸中观察到的复杂现象，例如外部和内部变形、可变滞后以及胸部解剖结构不同部分之间的可变相关性。这些限制使得对复杂的运动管理技术进行可靠的评估具有相当大的挑战性。在这项工作中，我们设计并实现了一种可编程的、外部和内部可变形的肺部运动体模，可在嵌入式标记物的外部-内部和内部-内部相关性方面实现可重复的变化。
一个内部设计的肺模块由天然乳胶泡沫制成，插入到市售肺体模（RSD，长滩，CA，美国）的外壳内。不透射线的标记物被放置在外部表面并嵌入到肺模块中。两个独立的可编程高精度线性运动执行器用于以可重复的方式产生主要前后（AP）和主要上下（SI）运动，以实现（a）内部容积的位移与外部表面之间的可变相关性，（b）AP 和 SI 运动幅度的独立变化，以及（c）可变滞后。通过用数学和患者记录的肺部肿瘤运动轨迹编程两个执行器，并使用千伏荧光透视法记录各种标记物的轨迹，评估体模准确且可重复地产生复杂和可变运动的能力。作为一个示例应用，该体模用于评估从千伏荧光透视和 4DCT 图像构建的肺部运动模型的性能。
该体模表现出高度的可重复性，并且标记物的运动范围可重复至 0.5mm 以内。在内部-内部和内部-外部标记物的位移之间观察到可变相关性。特定标记物的 SI 和 AP 运动分量的相关参数在-11 到 17 之间变化。监测体模表面上的感兴趣区域以估计内部标记物运动导致的不确定性远低于监测单个点时的不确定性。
我们成功设计并实现了一种可编程的、外部和内部可变形的肺部运动体模，可在嵌入式标记物的外部-内部和内部-内部相关性方面实现可重复的变化。
