A performance comparison of flat-panel imager-based MV and kV cone-beam CT
A performance comparison of flat-panel imager-based MV and kV cone-beam CT
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DOI：
10.1118/1.1477234
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发表时间：
2002-06-01
期刊：
影响因子：
3.8
通讯作者：
Jaffray, DA
中科院分区：
文献类型：
--
作者：
Groh, BA;Siewerdsen, JH;Jaffray, DA
已经提出使用锥束计算机断层扫描(CBCT)来指导放射治疗的提供，研究人员已经检查了千伏和兆伏(MV)X射线束在这种CBCT系统的开发中的使用。本文分析了现有的和假设的各种CBCT探测器的固有对比度和信噪比(SNR)随成像剂量和物体大小的变化关系。将理论预测与使用大面积平板成像仪(FPI)在千伏能量下的实验研究结果进行了比较。测量是在两个不同的基于FPI的CBCT系统上进行的：一个台式原型包括一个FPI和千伏X射线源(100kVPx射线)，一个系统包括安装在医用直线加速器机架上的一个FPI系统(6 mVx射线)。体积重建中的信噪比作为剂量的函数进行了测量，发现与理论预测合理一致。这些结果证实了使用千伏能量X射线成像人体软组织结构的理论预测的优势。虽然MV CBCT可以提供纠正3D设置错误的宝贵手段，并且在与线性加速器的机械集成的简单性方面具有优势(例如，实现替代门户成像器)，但在用于软组织结构可视化的图像对比度和每单位剂量的信噪比方面，千伏CBCT具有显著的性能优势。毫伏能量下相对较差的信噪比性能主要是由于X射线量子效率较低(类似于几个百分点或更低)，这是目前在高能下使用FP I实现的。此外，带有FPI的千伏CBCT提供了使用同一设备进行体积成像和放射/透视成像的可能性。2002年美国物理学家医学协会。
The use of cone-beam computed tomography (CBCT) has been proposed for guiding the delivery of radiation therapy, and investigators have examined the use of both kilovoltage (kV) and megavoltage (MV) x-ray beams in the development of such CBCT systems. In this paper, the inherent contrast and signal-to-noise ratio (SNR) performance for a variety of existing and hypothetical detectors for CBCT are investigated analytically as a function of imaging dose and object size. Theoretical predictions are compared to the results of experimental investigations employing large-area flat-panel imagers (FPIs) at kV and MV energies. Measurements were performed on two different FPI-based CBCT systems: a bench-top prototype incorporating an FPI and kV x-ray source (100 kVp x rays), and a system incorporating an FPI mounted on the gantry of a medical linear accelerator (6 MV x rays). The SNR in volume reconstructions was measured as a function of dose and found to agree reasonably with theoretical predictions. These results confirm the theoretically predicted advantages of employing kV energy x rays in imaging soft-tissue structures found in the human body. While MV CBCT may provide a valuable means of correcting 3D setup errors and may offer an advantage in terms of simplicity of mechanical integration with a linear accelerator (e.g., implementation in place of a portal imager), kV CBCT offers significant performance advantages in terms of image contrast and SNR per unit dose for visualization of soft-tissue structures. The relatively poor SNR performance at MV energies is primarily a result of the low x-ray quantum efficiencies (similar toa few percent or less) that are currently achieved with FPIs at high energies. Furthermore, kV CBCT with an FPI offers the potential of combined volumetric and radiographic/fluoroscopic imaging using the same device. 2002 American Association of Physicists in Medicine.