目的：探讨单源双能CT不同扫描野对标准体模CT能谱成像的CT值及水（碘）浓度值的影响。材料与方法：应用GE公司单源双能CT（Discovery HD750）对标准水模进行GSI模式扫描，依据扫描协议，按扫描野分为两组：Large扫描野组（L组）和Medium扫描野组（M组），其余扫描条件一致，具体参数如下：管电压为140 kVp和80 kVp瞬时切换，螺距为1.375，层厚为5 mm，管球电流及旋转时间在180～225 mAs范围进行调制，共扫描6层，扫描完成后以1.25 mm层厚进行无间隔标准算法重建。重建图像包括70 keV单能量图像及水（碘）基物质图像。由两名观察者独立进行数据分析测量，图像分析与测量均在AW4.5工作站进行，测量时以水模图像中心为原点，将面积为3 000 mm2的圆形感兴趣区（ROI）分别放置于水模正中、前、后、左、右5个位置，ROI距体模切缘约9 mm，在单能量及水基图像上分别测量每组6个层面不同位置的CT值及其SD值、水浓度值及其SD值，使用组内相关系数（ICC）检验两观察者测量值的一致性，选择标准差小的数据进行分析。使用配对样本t检验比较两组数据是否存在差异，以P<0.05为差异有统计学意义；以标准水模CT值为0 HU、水浓度值为1 000 mg/cm3作为金标准，分别将两组不同位置的CT值、水（碘）浓度值与金标准对照。结果：两观察者测量计算一致性良好，ICC值均＞0.75。①两组CT值比较，两组间CT值及其SD值比较差异均有统计学意义（P＜0.05），M组及L组CT值的均值分别为（3.07±1.49） HU、（2.11±2.47） HU，CT值M组均小于L组，M组更接近金标准，SD值M组大于L组。②两组水（碘）浓度值比较，两组间水（碘）浓度值及SD值比较差异均有统计学意义（P＜0.05），M组平均水浓度值为（1 001.86±1.99） mg/cm3，其平均SD值为4.70±0.50，L组平均水浓度值为（1 002.24±1.88） mg/cm3，其平均SD值为4.31±1.42，CT值M组均小于L组，M组与金标准更接近，SD值M组大于L组。③两组中两种方法的SD差异比较，每组中水（碘）浓度值的SD值均小于CT值的SD值，差异有统计学意义（P=0.000）。结论：扫描视野的改变可影响能谱成像CT值及水（碘）浓度值的测定，Medium扫描野优于Large扫描野，两组相比于传统CT，能谱成像受扫描野改变的影响更小，可更准确地用于定量分析。

Objective: To investigate the effect of different scan field of views(FOVs) on CT value, water-iodine concentration and SD value of standard water phantom by single-source dual-energy CT. Methods: A standard water phantom(GE, USA) was scanned by a single-source dual-energy CT scanner(GE Discovery 750HD, USA) with large and medium FOV, respectively(group L: large FOV; group M: medium FOV)． The other parameters were as follows: tube voltage switched instantaneously between 140 kVp and 80 kVp. Current modulation changed from 165 to 262.5 mAs. Thickness was 5 mm and pitch was 1.375. Each protocol collected 6 images and reconstructed into images with 1.25 mm-thickness. Circular ROI with area of around 3 000 mm2 was put in the middle, front, back, left and right of the water phantom, respectively on AW4.5 workstation. CT value and SD value of two groups were measured on the 70 keV monochromatic image. And water-iodine concentration and SD value were measured on the water-iodine concentration image. Independent-samples t test was used for statistical analysis. Results: There were statistical differences of CT value and SD value between group M and L(P＜0.05)． CT value of group M((3.07±1.49) HU) was less than that of group L((2.11±2.47) HU), closer to the gold standard. SD value of group M was bigger than group L. There was a significant difference of water-iodine concentration between group M and L(P＜0.05)． The SD value of water-iodine concentration was significantly lower than that of CT value between group M and L(P<0.001). Conclusion: The CT value and water-iodine concentration can be affected by scanning field of view. And medium scanning field is better than large scanning field. Compared with conventional CT, the change of scanning field has less effect on spectral CT which can be more accurate for quantitative analysis.