双源CT 70与120 kV不同CARE Dose 4D预设值下图像质量的对比研究

Comparative study on 70 and 120 kV dual-source CT image quality with different CARE Dose 4D preset values

目的:探讨双源CT不同管电压和CARE Dose 4D预设值下的辐射剂量与图像质量相关性,为低剂量扫描方案奠定基础。方法:使用西门子FLASH双源CT对水模进行图像采集。根据管电压分为A、B 2组,A组:管电压70 kV,B组:管电压120 k V。每组CARE Dose 4D预设值均为150、200、250、300、350和400 m As,其他参数不变。采用SPSS 18.0软件对CT值、图像信噪比(signal noise ratio,SNR)、剂量长度乘积(dose length produce,DLP)、容积CT剂量指数(CT dose index volumes,CTDIvol)进行统计分析,以P<0.05为差异有统计学意义。结果:在A组中,不同预设值间CT值无统计学差异(F=0.832,P=0.537>0.05),CT值标准差具有统计学差异(F=6.115,P=0.001<0.05);在B组中,不同预设值间CT值无统计学差异(F=0.880,P=0.506>0.05),CT值标准差具有统计学差异(F=9.470,P=0.000<0.05)。在相同预设值150 mAs下,A组和B组间CT值和SNR值无统计学差异(P>0.05),B组的CTDIvol和DLP是A组的4.4倍。结论:在相同的管电压下,随着CARE Dose 4D预设值增加,辐射剂量增大,噪声降低,图像质量提高;在相同的CARE Dose4D预设值下,70 k V下降低了辐射剂量,但与120 k V下图像质量没有统计学差异。

Objective To explore the correlation between radiation dose and image quality under different tube voltages of dual-source CT and preset values of CARE Dose 4D to lay a foundation for low-dose scanning scheme. Methods The images were collected by Siemens FLASH dual-source CT, and then divided into Group A with tube voltage 70 kV and Group B with tube voltage 120 kV. Preset values of CARE Dose 4D in each group were 150, 200, 250, 300, 350 and 400 mAs, respectively. Other parameters were kept unchanged. The obtained images were statistically analyzed by CT value, SNR, DLP, and CTDIvol, and P<0.05 was considered statistically significant. Results In Group A, there were no significant differences between the CT values with different preset values (F=0.832, P=0.537 >0.05), while the standard deviations of CT values showed statistical differences (F=6.115, P=0.001<0.05). In Group B, there were no statistical differences in the CT values (F=0.880, P=0.506 >0.05), while the standard deviations of CT values showed statistical differences (F=9.470, P=0.000<0.05). With the preset value kept as 150 mAs, there were no obvious differences between the CT values and SNR values of Group A and B, and the CTDIvol and DLP of Group B were 4.4 times as high as those of Group A. Conclusion Under the same tube voltage, radiation dose increases, noise decreases and image quality advances with the rising of CARE Dose 4D preset values;under the same CARE Dose 4D preset value, the radiation dose decreases with 70 kV tube voltage while the image quality with 70 kV tube voltage is not significantly different from that with 120 kV voltage.