不同前置滤线器对64层螺旋CT冠状动脉成像质量及放射剂量影响的对照研究

A comparative study of the influence of different bowtie of 64 multi-slice CT on cardiac image quality and radiation dosage

目的通过对选用不同前置滤线器模式所得到的图像质量和放射剂量的对照研究,探讨64层螺旋 CT(MSCT)冠状动脉成像时以较低放射剂量获得较高图像质量的可行性。方法按照统一的纳入标准,连续选取60例患者,进行 CT 冠状动脉检查。将患者分为 L、C 2组,每组30例。L 组选用体部滤线器(large bowtie)模式,C 组选用心脏滤线器(cardiac bowtie)模式。扫描中采用相同的参数,由2名有经验的影像诊断医师以双盲法分别对 L、C 组图像进行质量评分,测量各组图像噪声值,计算其均值及标准差,记录并比较 L 和 C 组平均 CT 剂量指数(CTDI)、剂量长度乘积(DLP)和有效剂量(ED)的差值。对2组图像质量评分、噪声值、CTDI、DLP 及 ED 值差异进行统计学分析。结果(1)L、C 2组图像质量评分分别为3.72、3.73分,2组间差异无统计学意义(t=0.17 P>0.05);(2)L、C 2组图像噪声值均值分别为30.05、27.80,C 组图像噪声明显低于 L 组(降低约7.5%),2组间差异有统计学意义(t=3.59,P<0.05);(3)L、C 2组平均 CTDI、DLP、ED 分别为83.97和77.66 mGy;1007.64和931.92 mGy/cm;17.13和15.84 mSy。C 组 CTDI、DLP、ED 明显低于L组(降低约7.5%),2组差异有统计学意义(P 均<0.01)。结论在64层 MSCT 冠状动脉成像时使用心脏滤线器模式可以有效地减少受检者接受的 X 线剂量,同时可以得到高质量的诊断图像。

Objective To evaluate the influence of different bowtie of 64 multi-slice CT on cardiac image quality and radiation dosage. Methods 60 patients （38 male and 22 female, average age of 55.4） underwent cardiac scans using 64 MSCT were divided into two groups with 30 patients each. The scanning protocol： 120 kV; scanning time： 0. 35 s/r; pitch： 0.20-0. 26; slice thickness： 0. 625 mm. The patient demography in terms of sex, age, height, weight and heart rate were similar for the two groups. The cardiac scans was performed using the large bowtie （group L） and cardiac bowtie （group C）, respectively, and recorded the CTDIw values for each group to reflect overall radiation dose to patients. Two experienced radiologists quantitatively evaluated the image quality blindly. The image noises were measured at the same time for the two sets. We performed statistical analyses on the quality scores, the noise measurements and the effective dose measurements from the two sets using t-test with the SPSS 10. 0 software. Results The image quality scores for the L and C groups were 3.72 and 3.73, respectively, with t-test of P 〉0. 05 indicating no statistical difference. However, the noise measurements for the L and C groups were 30. 05 and 27. 80, respectively, with P 〈 0. 05, indicating statistically significant lower image noise with cardiac bowtie. In addition, the CTDIw, DLP, Effective dose values were 83.97 mGy, 1007. 64 mGy/cm, 7. 96 mSv and 77. 66 mGy, 931.92 mGy/cm, 7. 36 mSv, respectively, for groups L and C with t-test of P 〈0. 01 indicating statistically significant lower dosage with cardiac bowtie. Conclusion The cardiac bowtie on 64 MSCT reduced the overall dosage to patients and image noise without adverse influences on other clinically relevant parameters.