From the *Department of Medical and Occupational Radiation Protection, Federal Office for Radiation Protection, Neuherberg; †Department of Urology, ‡Institute of Clinical Radiology and Nuclear Medicine, Medical Centre Mannheim, Mannheim; and §Abteilung für Radiologie, Allgemeines Krankenhaus Celle, Celle, Germany.
Invest Radiol. 2014 Oct;49(10):675-84. doi: 10.1097/RLI.0000000000000069.
Recent technical developments have facilitated the application of cone-beam computed tomography (CBCT) for interventional and intraoperative imaging. The aim of this study was to compare the radiation doses and image quality in CBCT with those of conventional multislice spiral computed tomography (MSCT) for abdominal and genitourinary imaging.
Different CBCT and MSCT protocols for imaging soft tissues and hard-contrast objects at different dose levels were investigated in this study. Local skin and organ doses were measured with thermoluminescent dosimeters placed in an anthropomorphic phantom. Moreover, the contrast-to-noise ratio, the noise-power spectrum, and the high-contrast resolution derived from the modulation transfer function were determined in a phantom with the same absorption properties as those of anthropomorphic phantom.
The effective dose of the examined abdominal/genitourinary CBCT protocols ranged between 0.35 mSv and 18.1 mSv. As compared with MSCT, the local skin dose of CBCT examinations could locally reach much higher doses up to 190 mGy. The effective dose necessary to realize the same contrast-to-noise ratio with CBCT and MSCT depended on the MSCT convolution kernel: the MSCT dose was smaller than the corresponding CBCT dose for a soft kernel but higher than that for a hard kernel. The noise-power spectrum of the CBCT images at tube voltages of 85/90 kV(p) is at least half of that of images measured at 103/115 kV(p) at any arbitrarily chosen spatial frequency. Although the pixel size and slice thickness of CBCT were half of those of the MSCT images, high-contrast resolution was inferior to the MSCT images reconstructed with a hard convolution kernel.
As compared with MSCT using a medium-hard convolution kernel, CBCT produces images at medium noise levels and, simultaneously, medium spatial resolution at approximately the same dose. It is well suited for visualizing hard-contrast objects in the abdomen with relatively low image noise and patient dose. For the detection of low-contrast objects at standard tube voltages of approximately 120 kV(p), however, MSCT should be preferred.
最近的技术发展促进了锥形束 CT（CBCT）在介入和术中成像中的应用。本研究旨在比较 CBCT 和传统多层螺旋 CT（MSCT）在腹部和泌尿生殖系统成像中的辐射剂量和图像质量。
本研究研究了不同的 CBCT 和 MSCT 协议，用于在不同剂量水平下对软组织和硬对比物体进行成像。使用放置在人体模型中的热释光剂量计测量局部皮肤和器官剂量。此外，在具有与人体模型相同的吸收特性的体模中，确定对比度噪声比、噪声功率谱和从调制传递函数得出的高对比度分辨率。
所检查的腹部/泌尿生殖系统 CBCT 方案的有效剂量范围为 0.35 mSv 至 18.1 mSv。与 MSCT 相比，CBCT 检查的局部皮肤剂量在局部可达到高达 190 mGy 的更高剂量。为了实现与 CBCT 和 MSCT 相同的对比度噪声比，所需的有效剂量取决于 MSCT 卷积核：对于软核，MSCT 剂量小于相应的 CBCT 剂量，但对于硬核，MSCT 剂量大于 CBCT 剂量。在管电压为 85/90 kV(p) 时，CBCT 图像的噪声功率谱至少是在任何任意选择的空间频率下测量的 103/115 kV(p) 图像的一半。尽管 CBCT 的像素大小和切片厚度是 MSCT 图像的一半，但高对比度分辨率不如用硬卷积核重建的 MSCT 图像。
与使用中硬卷积核的 MSCT 相比，CBCT 以中等噪声水平生成图像，同时在大致相同的剂量下具有中等空间分辨率。它非常适合用于可视化腹部中的硬对比物体，具有相对较低的图像噪声和患者剂量。然而，对于在约 120 kV(p) 的标准管电压下检测低对比度物体，应首选 MSCT。
