Reynolds Tess, Dillon Owen, Ma Yiqun, Hindley Nicholas, Stayman J Webster, Bazalova-Carter Magdalena
University of Sydney, Sydney, NSW, Australia.
Johns Hopkins University, Baltimore, MD, USA.
Phys Eng Sci Med. 2024 Dec;47(4):1751-1762. doi: 10.1007/s13246-024-01491-0. Epub 2024 Oct 24.
Increasingly, interventional thoracic workflows utilize cone-beam CT (CBCT) to improve navigational and diagnostic yield. Here, we investigate the feasibility of implementing free-breathing 4D respiratory CBCT for motion mitigated imaging in patients unable to perform a breath-hold or without suspending mechanical ventilation during thoracic interventions. Circular 4D respiratory CBCT imaging trajectories were implemented on a clinical robotic CBCT system using additional real-time control hardware. The circular trajectories consisted of 1 × 360° circle at 0° tilt with fixed gantry velocities of 2°/s, 10°/s, and 20°/s. The imaging target was an in-house developed anthropomorphic breathing thorax phantom with deformable lungs and 3D-printed imaging targets. The phantom was programmed to reproduce 3 patient-measured breathing traces. Following image acquisition, projections were retrospectively binned into ten respiratory phases and reconstructed using filtered back projection, model-based, and iterative motion compensated algorithms. A conventional circular acquisition on the system of the free-breathing phantom was used as comparator. Edge Response Width (ERW) of the imaging target boundaries and Contrast-to-Noise Ratio (CNR) were used for image quality quantification. All acquisitions across all traces considered displayed visual evidence of motion blurring, and this was reflected in the quantitative measurements. Additionally, all the 4D respiratory acquisitions displayed a lower contrast compared to the conventional acquisitions for all three traces considered. Overall, the current implementation of 4D respiratory CBCT explored in this study with various gantry velocities combined with motion compensated algorithms improved image sharpness for the slower gantry rotations considered (2°/s and 10°/s) compared to conventional acquisitions over a variety of patient traces.
越来越多的介入性胸部工作流程利用锥形束CT（CBCT）来提高导航和诊断效率。在此，我们研究了在胸部介入过程中无法屏气或未暂停机械通气的患者中实施自由呼吸4D呼吸CBCT以减轻运动影响成像的可行性。使用额外的实时控制硬件在临床机器人CBCT系统上实现了圆形4D呼吸CBCT成像轨迹。圆形轨迹由在0°倾斜下的1×360°圆组成，固定机架速度分别为2°/秒、10°/秒和20°/秒。成像目标是一个内部开发的具有可变形肺部的拟人化呼吸胸部模型和3D打印成像目标。该模型被编程以重现3条患者测量的呼吸轨迹。图像采集后，投影被回顾性地划分为十个呼吸阶段，并使用滤波反投影、基于模型和迭代运动补偿算法进行重建。在自由呼吸模型系统上的传统圆形采集用作对照。成像目标边界的边缘响应宽度（ERW）和对比度噪声比（CNR）用于图像质量量化。考虑的所有轨迹的所有采集都显示出运动模糊的视觉证据，这在定量测量中得到了反映。此外，对于所考虑的所有三条轨迹，所有4D呼吸采集的对比度均低于传统采集。总体而言，本研究中探索的4D呼吸CBCT当前实施方案，结合各种机架速度和运动补偿算法，与传统采集相比，对于所考虑的较慢机架旋转速度（2°/秒和10°/秒）在各种患者轨迹上提高了图像清晰度。
