应用全模型迭代重建技术的低剂量CT肝脏体积测定的临床应用价值

Liver volume measurement with low dose CT using iterative model reconstruction technique

目的:探讨低剂量下全模型迭代重建(iterative model reconstruction,IMR)技术在肝脏体积测定中的应用。方法:将40例受检者的常规剂量肝脏增强计算机体层成像(computed tomography,CT)门静脉期图像采用滤波反投影(filter back projection,FBP)重建并标记为A组;低剂量肝脏增强CT延迟期图像采用IMR并标记为B组。对两组图像的肝脏边缘锐利度、肝段分界标志锐利度进行主观评价,采用Philips星云工作站中的肝脏分段软件对肝脏进行三维重建,根据Couinaud分段测得肝脏总体积及Ⅰ~Ⅷ段体积,并计算肝段体积比(liver segmental volume ratio,LSVR)。两组图像主观评价比较采用Wilcoxon符号秩检验;两组图像客观指标及辐射剂量的比较采用配对样本t检验。结果:B组对于A组主观评价差异有统计学意义(Z=-4.025,P<0.05),A组中位数(3分)低于B组(4分)。A、B组肝脏总体积分别为(1 197.75±215.50)、(1 193.17±214.70)mL;肝Ⅰ段体积分别为(18.28±8.79)、(18.45±8.59)mL;肝Ⅱ段体积分别为(100.99±33.17)、(98.28±33.58)mL;肝Ⅲ段体积分别为(127.02±60.49)、(126.40±57.82)mL;肝Ⅳ段体积分别为(178.84±53.83)、(178.08±51.57)mL;肝Ⅴ段体积分别为(165.67±53.88)、(169.16±61.09)mL;肝Ⅵ段体积分别为(132.41±62.95)、(129.36±59.28)mL;肝Ⅶ段体积分别为(180.58±69.35)、(175.36±65.74)mL;肝Ⅷ段体积分别为(253.34±68.82)、(248.63±63.50)mL。A、B组之间肝脏总体积、肝Ⅰ~Ⅷ段体积及LSVR差异均无统计学意义(P>0.05)。B组对于A组有效剂量均降低75%以上。结论:低剂量条件下应用IMR技术对比常规剂量FBP重建可以明显降低剂量,提高肝脏边缘锐利度,可准确重建肝段图像,并且得到准确的总肝体积、肝Ⅰ~Ⅷ段体积及LSVR的定量数据。

Objective:To explore the application of iterative model reconstruction(IMR)technique in the determination of liver volume at low dose.Methods:Under conventional dose condition,the portal phase images of liver-enhanced CT of 40 subjects were reconstructed by filter back projection(FBP)and labeled as group A;while under low dose condition,the images were reconstructed by IMR and labeled as group B.The edge sharpness of the liver and the sharpness of the liver segment boundary markers in the two groups were subjectively evaluated.The liver was reconstructed by the liver segmentation software in the Philips IntelliSpace Portal,and the total liver volume andⅠ-Ⅷsegment volume were measured according to the Couinaud segment.The liver segment volume ratio(LSVR)was calculated.The subjective evaluation of the two groups of images was compared by Wilcoxon signed rank test,and the objective indexes and radiation dose of the two groups were compared by paired sample t test.Results:The subjective evaluation between group A and group B was statistically significant(Z=-4.025,P<0.05),the median of group A was lower than that of group B,and the median of group A was 3 and the median of group B was 4.The total volume of liver in group A and B was(1197.75±215.50)and (1 193.17±214.70) mL, respectively. The volume of hepatic segment Ⅰ was (18.28±8.79) and (18.45±8.59) mL, respectively.The volume of hepatic Ⅱ segment was (100.99±33.17) and (98.28±33.58) mL, respectively. The volume of Ⅲ segment of liverwas (127.02±60.49) and (126.40±57.82) mL, respectively. The volume of Ⅳ segment of liver was (178.84±53.83) and (178.08±51.57) mL, respectively. The volume of Ⅴ segment of liver was (165.67±53.88) and (169.16±61.09) mL, respectively. The volumeof liver Ⅵ segment was (132.41±62.95) and (129.36±59.28) mL, respectively. The volume of liver Ⅶ segment was (180.58±69.35)and (175.36±65.74) mL, respectively. The volume of liver Ⅷ segment was (253.34±68.82) and (248.63±63.50) mL, respectively.There was no significant difference in the total volume of liver, the volume of Ⅰ-Ⅷ segment and the volume ratio of liver segmentbetween group A and group B. The effective dose of group B for group A was reduced by more than 75%. Conclusion: Comparedwith conventional dose FBP reconstruction, IMR technique at low dose can significantly reduce the dose, improve the sharpness ofliver edge, and reconstruct liver segment image accurately. The quantitative data of total liver volume, liver Ⅰ-Ⅷ segment volumeand LSVR also can be obtained.