心电门控64排CT评价肾下型腹主动脉瘤弹性的初步研究

A Preliminary Study of Assessing Aortic Elasticity in Infrarenal Abdominal Aortic Aneurysm with Electrocardiographically Gated 64-Detector Row CT

目的探讨心电门控技术64排CT评价肾下型腹主动脉瘤主动脉弹性的临床价值。方法 26例受检者分为腹主动脉瘤组13例,正常对照者组13例,均行腹主动脉CTA检查。两组间受检者性别及年龄完全匹配。所有受检者均采用64排螺旋CT、回顾性心电门控技术和分段数据采集方式。获得的原始数据分别在0%~95%R-R间期、间隔5%重组图像,然后在肾动脉水平(renal)和肾动脉下(infrarenal)采用MATLAB图像分割软件,分别测量各重建期相主动脉的横断面积。完成CT扫描后由专人常规测量受检者血压。最后通过公式计算主动脉弹性D值和脉搏波波速(PWV)。结果腹主动脉瘤组D_(renal)值和D_(infra)值分别为(1.21±0.40)×10^(-5)Pa^(-1)、(0.68±0.36)×10^(-5)Pa^(-1),对应的PWV值分别为(9.19±1.59)m/s、(13.37±4.84)m/s。正常对照组D_(renal)值和D_(infra)值分别为(1.92±0.27)×10^(-5)Pa^(-1)、(1.24±0.37)×10^(-5)Pa^(-1),对应的PWV值分别为(7.07±0.52)m/s和(9.15±2.04)m/s。腹主动脉瘤组及对照组内D_(renal)值、D_(infra)值差异有统计学意义(t值分别为5.668、7.966,P值均<0.05),其Drenal值均大于Dinfra值。腹主动脉瘤组与对照组间Drenal值比较差异有统计学意义(t值为-5.852,P值<0.05),两组间Dinfra值的差异亦有统计学意义(t值为-4.417,P值<0.05),腹主动脉瘤组均小于对照组,D值对应的PWV值比较也有一致的结果。Bland-Altman一致性检验显示心电门控64排CT所测得腹主动脉弹性值观察者间、观察者内相关性良好,一致性较高。结论心电门控64排CT可以定量评价肾下型腹主动脉瘤的弹性变化。肾下型腹主动脉瘤弹性较正常腹主动脉下降,而且正常瘤体近端主动脉的弹性也下降。

Objective To determine the feasibility of assessment of aortic distensibility with multiphase analysis of data sets of retrospective electrocardiogram（ECG）-gated 64-detector row computed tomography（MDCT） in infrarenal abdominal aortic aneurysm.Methods Thirteen patients with infrarenal abdominal aortic aneurysm（AAA） were enrolled.Thirteen healthy volunteers were included as a control group.Between the two groups of subjects,gender and age were perfectly matched.All the subjects underwent MDCT to evaluate the arterial distensibility（D） and pulse wave velocity（PWV）.Time-resolved images were acquired with a 64-detector row CT scanner（GE,Light Speed,VCT）,using a modified CT-angiography protocol.Scan data were reconstructed at 20 phases between 0% and 95% of the R-R intervals with an increment of 5%.Aortic cross-sectional area changes were determined at two positions of the aorta,immediately above the infrarenal AAA and at the level of its maximal diameter.Two familiar cardiovascular imaging diagnostic radiology doctors performed image segmentation based on MATLAB software.Personnel was designated to routinely measure blood pressure after completing CT scan.Finally,used the formula to calculate the aorta elastic D value.Results Vessel cross-sectional area could be measured successfully with the semiautomatic segmentation algorithm in all 26 subjects.In AAA group,distensibility at and below the origin of the renal arteries were（1.21 ± 0.40）×10^（-5）Pa^（-1）and（0.68 ± 0.36） × 10^（-5）Pa^（-1）respectively,while they were（1.92 ± 0.27）×10^（-5）Pa^（-1）and（1.24 ± 0.37） × 10^（-5）Pa^（-1）respectively in the control group.Drenal value was slightly higher than Dinfra value either in AAA group or control group（t = 5.668,7.966,P 〈0.05）.At the branching of the renal arteries or at the level of the aneurysm,mean distensibility in AAA group was significantly lower than that in control group（t=- 5.852,- 4.417,P0.05）.Statistical analysis of the PWV value changes,which corresponds to distensibility,also showed consistent results.The repeated elastic measurements respectively by two observers revealed a good agreement and reproducibility in inter-and intra-observers.Conclusion Infrarenal abdominal aortic aneurysm led to the loss of elasticity,and normal proximal aortic elasticity of the aneurysm was also affected; Multiphase analysis in ECG-gated MDCT enables us to quantitatively assess elastic changes of infrarenal abdominal aortic aneurysm.