LXi Research, Division of Medical Physics, University of Leeds, Worsley Building, Clarendon Way, Leeds LS2 9JT, United Kingdom.
Med Phys. 2013 Sep;40(9):091911. doi: 10.1118/1.4818016.
The aim of this research was to optimize x-ray image quality to dose ratios in the cardiac catheterization laboratory. This study examined independently the effects of peak x-ray tube voltage (kVp), copper (Cu), and gadolinium (Gd) x-ray beam filtration on the image quality to radiation dose balance for adult patient sizes.
Image sequences of polymethyl methacrylate (PMMA) phantoms representing two adult patient sizes were captured using a modern flat panel detector based x-ray imaging system. Tin and copper test details were used to simulate iodine-based contrast medium and stents∕guide wires respectively, which are used in clinical procedures. Noise measurement for a flat field image and test detail contrast were used to calculate the contrast to noise ratio (CNR). Entrance surface dose (ESD) and effective dose measurements were obtained to calculate the figure of merit (FOM), CNR(2)∕dose. This FOM determined the dose efficiency of x-ray spectra investigated. Images were captured with 0.0, 0.1, 0.25, 0.4, and 0.9 mm Cu filtration and with a range of gadolinium oxysulphide (Gd2O2S) filtration.
Optimum x-ray spectra were the same for the tin and copper test details. Lower peak tube voltages were generally favored. For the 20 cm phantom, using 2 Lanex Fast Back Gd2O2S screens as x-ray filtration at 65 kVp provided the highest FOM considering ESD and effective dose. Considering ESD, this FOM was only marginally larger than that from using 0.4 mm Cu at 65 kVp. For the 30 cm phantom, using 0.25 mm copper filtration at 80 kVp was most optimal; considering effective dose the FOM was highest with no filtration at 65 kVp.
These settings, adjusted for x-ray tube loading limits and clinically acceptable image quality, should provide a useful option for optimizing patient dose to image quality in cardiac x-ray imaging. The same optimal x-ray beam spectra were found for both the tin and copper details, suggesting that iodine contrast based imaging and visualization of interventional devices could potentially be optimized for dose using similar x-ray beam spectra.
本研究旨在优化心脏导管室的 X 射线图像质量与剂量比。本研究分别研究了峰值 X 射线管电压（kVp）、铜（Cu）和镓（Gd）X 射线束滤波对成人患者尺寸的图像质量与辐射剂量平衡的影响。
使用现代平板探测器 X 射线成像系统拍摄代表两个成人患者尺寸的聚甲基丙烯酸甲酯（PMMA）体模的图像序列。锡和铜测试细节用于模拟碘基造影剂和支架/导丝，这些在临床程序中使用。使用平面场图像的噪声测量和测试细节对比度来计算对比噪声比（CNR）。获取入射表面剂量（ESD）和有效剂量测量值以计算品质因数（FOM），即 CNR(2)/剂量。该 FOM 确定了所研究的 X 射线光谱的剂量效率。使用 0.0、0.1、0.25、0.4 和 0.9mm Cu 滤波以及一系列氧化镓（Gd2O2S）滤波拍摄图像。
对于锡和铜测试细节，最佳 X 射线光谱相同。通常优选较低的峰值管电压。对于 20cm 体模，在 65kVp 时使用 2 个 Lanex Fast Back Gd2O2S 屏幕作为 X 射线滤波，在考虑 ESD 和有效剂量的情况下，提供了最高的 FOM。考虑 ESD，此 FOM 仅略大于在 65kVp 时使用 0.4mmCu 的 FOM。对于 30cm 体模，在 80kVp 时使用 0.25mm 铜滤波最为优化；在不考虑有效剂量的情况下，使用 65kVp 时无滤波的 FOM 最高。
这些设置针对 X 射线管加载限制和临床可接受的图像质量进行了调整，应可为心脏 X 射线成像中的患者剂量与图像质量优化提供有用的选择。对于锡和铜细节，发现相同的最佳 X 射线束光谱，这表明碘基造影剂成像和介入设备可视化可能可以使用类似的 X 射线束光谱进行剂量优化。
