A mobile isocentric C-arm for intraoperative cone-beam CT: Technical assessment of dose and 3D imaging performance.
A mobile isocentric C-arm for intraoperative cone-beam CT: Technical assessment of dose and 3D imaging performance.
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DOI：
10.1002/mp.13983
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发表时间：
2020-03
期刊：
影响因子：
3.8
通讯作者：
Siewerdsen JH
中科院分区：
文献类型：
--
作者：
Sheth NM;De Silva T;Uneri A;Ketcha M;Han R;Vijayan R;Osgood GM;Siewerdsen JH
旨在表征最近开发的移动的、配备平板探测器（FPD）的等中心C形臂的辐射剂量和三维（3D）成像性能，用于术中锥形束计算机断层扫描（CBCT）（Cios Spin 3D，Siemens Healthineers），并确定相关成像任务的3D成像方案的潜在改进。C形臂具有30 × 30 cm 2 FPD和等中心机架，具有计算机控制的旋转（0-195°）、成角（±220°）和高度（0-45 cm）电动化。根据CBCT扫描中X射线源和探测器的9个自由度评估几何校准，并评价几何校准的再现性。评价了标准和定制扫描方案，每个视图的投影数量（100-400）和mAs（0.05-1.65 mAs）不同。图像重建基于使用“平滑”、“正常”和“锐化”重建滤波器以及自定义二维各向同性滤波器的3D滤波反投影。成像性能的均匀性，灰度值对应亨氏单位（HU），对比度，噪声（噪声功率谱，MTF），空间分辨率（调制传递函数，MTF），和噪声等效量子（NEQ）方面进行了评价。在不同解剖部位和成像任务的拟人模型中，可以看到协议之间的性能权衡。几何校准显示出高度的再现性，尽管在标称半圆形轨道上有约19 mm的机架弯曲。CBCT扫描的剂量从头部方案的约0.8-4.7 mGy到身体方案的约6-38 mGy不等。MTF与亚毫米空间分辨率一致，平滑滤波器、标准滤波器和锐化滤波器的f10（MTF = 10%时的频率）分别等于0.64 mm−1、1.0 mm−1和1.5 mm−1。自定义2D各向同性滤波器的实现将头部和身体协议的CNR提高了约50-60%，并提供了更多的各向同性分辨率和噪声特性。该模型和NEQ量化了3D噪声性能，并为协议选择提供了指导，在拟人幻影图像中得到了证实。根据身体部位和任务确定替代扫描方案-例如，足以使骨结构可视化的低剂量身体方案（<3 mGy）。这些研究对新型C形臂的剂量和3D成像性能进行了客观评估，为临床部署提供了重要依据，并为质量保证提供了基准。确定了对标准3D成像协议的修改，这些修改可以提高相关成像任务的性能或降低辐射剂量。
To characterize the radiation dose and three-dimensional (3D) imaging performance of a recently developed mobile, isocentric C-arm equipped with a flat-panel detector (FPD) for intraoperative cone-beam computed tomography (CBCT) (Cios Spin 3D, Siemens Healthineers) and to identify potential improvements in 3D imaging protocols for pertinent imaging tasks. The C-arm features a 30 × 30 cm2 FPD and isocentric gantry with computer-controlled motorization of rotation (0–195°), angulation (±220°), and height (0–45 cm). Geometric calibration was assessed in terms of 9 degrees of freedom of the x-ray source and detector in CBCT scans, and the reproducibility of geometric calibration was evaluated. Standard and custom scan protocols were evaluated, with variation in the number of projections (100–400) and mAs per view (0.05–1.65 mAs). Image reconstruction was based on 3D filtered backprojection using “smooth,” “normal,” and “sharp” reconstruction filters as well as a custom, two-dimensional 2D isotropic filter. Imaging performance was evaluated in terms of uniformity, gray value correspondence with Hounsfield units (HU), contrast, noise (noise-power spectrum, NPS), spatial resolution (modulation transfer function, MTF), and noise-equivalent quanta (NEQ). Performance tradeoffs among protocols were visualized in anthropomorphic phantoms for various anatomical sites and imaging tasks. Geometric calibration showed a high degree of reproducibility despite ~19 mm gantry flex over a nominal semicircular orbit. The dose for a CBCT scan varied from ~0.8–4.7 mGy for head protocols to ~6–38 mGy for body protocols. The MTF was consistent with sub-mm spatial resolution, with f10 (frequency at which MTF = 10%) equal to 0.64 mm−1, 1.0 mm−1, and 1.5 mm−1 for smooth, standard, and sharp filters respectively. Implementation of a custom 2D isotropic filter improved CNR ~ 50–60% for both head and body protocols and provided more isotropic resolution and noise characteristics. The NPS and NEQ quantified the 3D noise performance and provided a guide to protocol selection, confirmed in images of anthropomorphic phantoms. Alternative scan protocols were identified according to body site and task — for example, lower-dose body protocols (<3 mGy) sufficient for visualization of bone structures. The studies provided objective assessment of the dose and 3D imaging performance of a new C-arm, offering an important basis for clinical deployment and a benchmark for quality assurance. Modifications to standard 3D imaging protocols were identified that may improve performance or reduce radiation dose for pertinent imaging tasks.
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