体质量指数结合iDose^4迭代重建算法在低剂量冠状动脉CT成像中的应用

Application of iterative reconstruction technique(iDose^4) on dose reduction at body mass index-based CT coronary angiography

目的探讨基于受检者体质量指数(BMI)并应用前瞻性心电门控结合iDose4迭代重建技术降低冠状动脉CT成像(CTCA)辐射剂量的可行性。方法选取120例CTCA受检者,根据不同BMI将其分为4组,A组(BMI≤21kg/m2)、B组(21kg/m2<BMI≤24kg/m2)、C组(24kg/m2<BMI<28kg/m2)、D组(BMI≥28kg/m2),每组各30例。预设A组、B组、C组、D组管电流分别为100、150、200、250mAs,应用前瞻性心电门控技术进行扫描,之后采用iDose4迭代重建算法对图像分别进行标准滤波反投影(FBP)、iDose4-3、iDose4-5重建。由2名放射科医师采用4分制对图像质量进行主观评估,测量图像的客观噪声。记录4组的CT剂量指数(CTDIvol)、剂量长度乘积(DLP),并估算有效剂量(ED)。结果各组中3种重建图像的客观噪声差异有统计学意义(P<0.001)。与FBP相比,iDose4-3和iDose4-5的图像客观噪声分别平均降低23.11%和35.61%,且应用iDose4-3和iDose4-5重建算法获得的CTCA图像主观评分≥3分的比率高于FBP(P<0.05),但iDose4-3和iDose4-5之间的差异无统计学意义。4组受检者ED均值分别为(1.36±0.10)mSV、(1.98±0.10)mSV、(2.67±0.21)mSV和(3.33±0.24)mSV。结论应用前瞻性心电门控技术结合iDose4迭代重建技术,根据受检者BMI采用不同扫描参数,可有效减低CTCA辐射剂量。

Objective To explore the effect of iterative reconstruction technique （iDose4） on dose reduction at body mass index （BMI）-based CT coronary angiography （CTCA） with prospective gating. Methods A total of 120 patients who un- derwent CTCA with prospective gating were divided into 4 groups according to BMI, i.e. group A （BMI≤21 kg/m2 ）, group B （21 kg/m2〈BMI≤24 kg/m2）, group C （24 kg/m2〈BMI〈28 kg/m2） and group D （BMI≥28 kg/m2）, each group had 30 patients. The tube current was set as 100 mAs, 150 mAs, 200 mAs, and 250 mAs for group A to group D, respectively. Three series of images were reconstructed with filtered back projection （FBP）, iDose4-3 and iDose4-5 for each subject. Two radiologists assessed subjective image quality using 4-point scale. Objective image noise was measured. CT dose index volumes （CTDIvol） and dose length product （DLP） were recorded, while effective dose （ED） was estimated. Results In each group, significant differences among three reconstruction methods were found respect to objective image noise （all P^0. 001）. Compared with FBP, the objective image noise reduction was 23.11 % and 35.61% for iDose4-3 and iDose4-5 , respectively. The ratio of the subjective image score ≥3 of iDose4-3 and iDose4-5 images in each group was high- er than that of FBP images （P〈0.05）, while no statistical difference was found between iDose4-3 and iDose4-5. The aver- age ED of group A to group D was （1.36：±0.10）mSV, （1.98±0.10）mSV, （2.67±0.21）mSV and （3. 33±0.24）mSV, respectively. Conclusion BMI-based iterative reconstruction technique （iDose4） and prospective gating can effectively re- duce radiation dose of CTCA.