单源双能 CT 不同重建层厚对标准水模 GSI 数据的影响

目的：探讨单源双能 CT 不同重建层厚对标准水模能谱成像的 CT 值、水(碘)浓度、SD 值的影响。方法使用 GE 公司单源双能 CT(Discovery CT 750 HD),选择辐射剂量相近(165~262.5 mAs)的8个扫描协议,对 GE 20 cm 直径的水模行 CT 能谱成像(GSI)扫描,管电压采用140 kVp 和80 kVp 瞬时切换,扫描视野 medium,螺距1.375,探测器宽度40 mm,每个协议采集6层5 mm 层厚图像(B 组),重建1.25 mm 层厚图像(A 组)。使用 AW4.5工作站,将面积约3000 mm2的圆形感兴趣区(ROI)置于水模的中心、3点、6点、9点、12点的位置进行测量,分别在70 keV 单能量图像上测量 A、B 2组的 CT 值和 SD 值,在水(碘)基图像上测量水(碘)浓度和 SD 值,分别采用独立样本 t 检验、配对样本 t 检验进行统计学分析。结果A 组及 B 组 CT 值和水(碘)浓度的差异无统计学意义(P >0.05),SD 值的差异有统计学意义(P <0.05)。A、B 2组水(碘)浓度的 SD 值均小于 CT 值的 SD 值,差异有统计学意义(P <0.05)。结论重建层厚的改变不会影响单源双能 CT GSI 扫描的 CT 值和水(碘)浓度,对 SD 值有影响。GSI 对物质浓度的测量及 CT 值测量更加准确。

The effect of different reconstruction slice thickness on GSI data of standard water phantom by single-source dual-energy CT

Objective To investigate the effect of different reconstruction slice thickness on CT value,water-iodine concentration and SD value of standard water phantom by single-source dual-energy CT.Methods The 20 cm diameter standard water phantom (GE,USA)was scanned by single-source dual-energy CT machine(GE Discovery 750 HD,USA),with eight protocols which radiation dose about 1 65-262.5 mAs.Tube voltage was switched instantaneously by 140 kVp and 80 kVp,and the scanning field was medium. Pitch was 1.375 with the width of the detector as forty millimeters.For each protocol,6 images were collected with thickness of 5 millimeter (Group B)and then reconstructed with 1.25 millimeter-thickness (Group A).Put the circular regions of interest (ROI) with area around 3 000 mm2 on the centre,3 o'clock,6 o'clock,9 o'clock,12 o'clock position of water phantom by using AW4.5 workstation.CT value and SD value of two groups on the 70 keV single-energy image were measured,and water-iodine concentration and SD value were measured on the water-iodine material image.Independent-samples t test and paired-samples t test were used for statistical analysis. Results There was no statistical difference of CT value or water-iodine concentration between Group A and B (P >0.05).There was significantly statistical difference of SD value between Group A and B (P <0.05).The SD values of water-iodine concentration were signicantly lower than the SD values of CT value in Group A and B.Conclusion There is no effect of changing reconstruction slice thickness on CT value and water-iodine concentration by using single-source dual-energy CT,it has an impact on SD value.The water-iodine concentration and CT value measured by spectral CT are more accurately.