Lin Ming De, Samei Ehsan, Badea Cristian T, Yoshizumi Terry T, Johnson G Allan
Center for In Vivo Microscopy, Box 3302, Duke University Medical Center, Durham, North Carolina 27710, USA.
Med Phys. 2006 Nov;33(11):4249-57. doi: 10.1118/1.2356646.
The increasing use of small animals in basic research has spurred interest in new imaging methodologies. Digital subtraction angiography (DSA) offers a particularly appealing approach to functional imaging in the small animal. This study examines the optimal x-ray, molybdenum (Mo) or tungsten (W) target sources, and technique to produce the highest quality small animal functional subtraction angiograms in terms of contrast and signal-difference-to-noise ratio squared (SdNR2). Two limiting conditions were considered-normalization with respect to dose and normalization against tube loading. Image contrast and SdNR2 were simulated using an established x-ray model. DSA images of live rats were taken at two representative tube potentials for the W and Mo sources. Results show that for small animal DSA, the Mo source provides better contrast. However, with digital detectors, SdNR2 is the more relevant figure of merit. The W source operated at kVps >60 achieved a higher SdNR2. The highest SdNR2 was obtained at voltages above 90 kVp. However, operation at the higher potential results in significantly greater dose and tube load and reduced contrast quantization. A reasonable tradeoff can be achieved at tube potentials at the beginning of the performance plateau, around 70 kVp, where the relative gain in SdNR2 is the greatest.
基础研究中对小动物使用的不断增加激发了人们对新成像方法的兴趣。数字减影血管造影术（DSA）为小动物功能成像提供了一种特别有吸引力的方法。本研究考察了最佳的X射线、钼（Mo）或钨（W）靶源，以及就对比度和信号差与噪声比平方（SdNR2）而言产生最高质量小动物功能减影血管造影的技术。考虑了两个限制条件——剂量归一化和管负载归一化。使用已建立的X射线模型模拟图像对比度和SdNR2。在W和Mo源的两个代表性管电压下拍摄活大鼠的DSA图像。结果表明，对于小动物DSA，Mo源提供了更好的对比度。然而，对于数字探测器，SdNR2是更相关的品质因数。在千伏峰值（kVps）>60时运行的W源实现了更高的SdNR2。在高于90 kVp的电压下获得了最高的SdNR2。然而，在较高电位下运行会导致剂量和管负载显著增加以及对比度量化降低。在性能平稳期开始时的管电压（约70 kVp）下可以实现合理的权衡，此时SdNR2的相对增益最大。
