全模型迭代重建技术在冠状动脉钙化模体扫描中的应用价值研究

A study of iterative model reconstruction technology in a cardiac coronary calcium anthropomorphic phantom

目的:通过对心脏钙化模体常规剂量扫描滤过反投影重建(Filtered back projection,FBP)与不同级别低剂量扫描全模型迭代重建(Iterative model reconstruction,IMR)钙化积分及图像质量的比较,探讨IMR技术降低冠状动脉钙化积分(Coronary artery calcium score,CACS)扫描剂量的能力。材料与方法:以心脏钙化模体作为研究对象,以120 k V、80 m As结合FBP作为常规剂量组(A组);低剂量组管电压为120 k V,管电流逐级降为50 m As、40 m As、30 m As、20 m As,均采用IMR算法,记为B^E组。采用单因素方差分析比较各组总Agatston积分、总体积分数、总质量分数、不同密度组Agatston积分、不同直径组Agatston积分及噪声的差异,两两比较采用Bonferroni法,P<0.05为差异有显著的统计学意义。结果:各组间总Agatston积分、体积分数、质量分数、不同密度亚组及不同直径亚组Agatston积分均未见显著的统计学差异。E组噪声显著大于A组(16.5±2.6 vs 8.77±1.55,P=0.005),A组与B^D组噪声未见显著差异。D组辐射剂量较A组降低了62.41%((2.53±0.06)m Gy vs(6.73±0.23)m Gy)。结论:IMR可在低剂量下获得与常规剂量FBP重建相当的CACS值及图像质量,最适低剂量组为D组,120 k V、30 m As配合IMR算法,其辐射剂量比常规剂量组降低了62.41%。

Objective： To determine whether or not IMR with lower tube current could replace FBP with routine tube current, and to find the lowest possible tube current for coronary calcium scanning while maintaining accurate Agatston score, volumn score and mass score using a cadiac phantom. Meterials and Methods： An anthropomorphic thoracic and heart phantom containing 9 calcium-insert columns was used to measure the sum of the Agatston score, volumn score, mass score of the 9 columns, Agatston score of different diameter columns and different density columns. And then these measurements among different current and algorithm groups were compared. Using the measurements of 120 kV, 80 mAs with traditional FBP as gold standard （Group A）, the measurements with tube voltage 120 kV, and lower tube current of 50 mAs, 40 mAs, 30 mAs and 20 mAs with IMR algorithm were kept as group B, C, D and E, respectively. Then each measurement was compared with gold standard, with P〈0.05 as statistical significance. Result： There was no significant difference between each lower current group and group A. For noise, Group E was significantly higher than Group A （16.5±2.6 vs 8.77±1.55, P=0.005）. There was no significant difference between group A and group B-D. The radiation dose of group D was 62.41% lower than that of group A （（2.53±0.06） mGy vs （6.73±0.23）mGy）. Conclusion： Technology IMR with lower tube current could replace FBP with 80 mAs. The optimal low dose group is group D（IMR with 120 kV, 30 mAs）. The scanning dose of group D is 62.41% lower than group A.