迭代重建技术在CT低剂量检查骶髂关节中的应用

The application of low-dose CT iterative reconstruction of sacroiliac joint

目的评价使用迭代重建技术在双源CT检查骶髂关节成像中对图像质量和辐射剂量的影响。方法 60例因下腰部不适行双源CT骶髂关节检查的患者,随机分为两组:A组30例,参考管电流为60mAs,图像重建使用SAFIRE法;B组为对照组,也为30例,参考管电流为150mAs,图像重建使用常规FBP法。两组客观图像质量测量均选择在同一层面,分别于骨关节面下松质骨内、邻近肌肉和脂肪内选择感兴趣区(面积为100mm2),测量CT值、平均标准差(SD)作为噪声值,记录剂量长度乘积(dose-length product,DLP)。采用Likert 5分评价主观图像质量,并通过Kappa方法评价观察者间的一致性。结果两组在各相同松质骨内(218.00±64.57)HU vs(219.23±54.27)HU(P=0.936)、邻近肌肉内(55.67±7.45)HU vs(53.73±4.66)HU(P=0.233)、脂肪内(-97.67±10.60)HU vs(-95.30±14.62)HU(P=0.476),CT值差异均无统计学意义;图像噪声和主观图像质量评分差异也无统计学意义。两组DLP分别为(27.20±5.51)mSv vs(78.37±18.51)mSv,A组较B组分别降低了65.3%(P<0.001),差异有统计学意义。结论当使用低mAs(60mAs)联合迭代重建算法进行骶髂关节CT成像时,在保持图像质量的同时,还能极大降低有效辐射剂量。

Objective To investigate the impact of SAFIRE technique on image quality and radiation dose of sacroiliac joint dual‐source computed tomography .Methods 60 patients who underwent sacroiliac joint CT scan were randomly di‐vided into two groups .The patients in group A were scanned using the low tube current 60 mAs and images were recon‐structed using iterative reconstruction technique （SAFIRE ,Siemens Healthcare） .The patients in group B were scanned u‐sing the tube current 150 mAs and images were reconstructed using filtered back projection （FBP） .CT attenuation and noise was measured in the cancellous bone ,adjacent muscle and fat respectively .Subjective image quality scores and dose‐length product were compared between the two groups .Results There was no significant difference in the mean CT atten‐uation achieved ,image noise and mean image quality score in cancellous bone , adjacent muscle and fat between two groups .The DLP were （27 .20 ± 5 .51） mSv vs （78 .37 ± 18 .51） mSv for 60 mAs group and 150 mAs group respectively . Reflecting dose saving was 65 .3% （ P 〈 0 .001） .Conclusion The results demonstrate that with a combination of iterative reconstruction and a lower tube current （60 mAs） can keep the image quality ,as well as significantly lower DLP .