CT灌注在低注射流率时最大斜率法的准确性分析及改良

Analysis of Accuracy and Improvement of Maximum-Slope Method in CT Perfusion under the Condition of Low Injection Rate

目的:分析低流率注射条件下最大斜率法测量的准确性,寻找提高其准确性的改良方法。方法:40例健康成人随机等分成两组,分别以4 ml/s和2 ml/s的流率注入对比剂,行双肾皮质CT灌注扫描,以最大斜率法、改良最大斜率法、去卷积算法分别测量肾皮质灌注参数,以去卷积算法为标准评价最大斜率法、改良最大斜率法的准确性。统计软件为SAS 6.12,采用方差分析,检验水准α=0.05。结果:最大斜率法在低注射流率下会低估组织的血流量(Blood flow,BF),注射流率越低,低估的程度越高。改良最大斜率法与去卷积算法所得结果差异无显著性意义(P<0.05)。结论:可以通过改良最大斜率法使其适用于低注射流率条件下的CT组织灌注测量的近似计算。

Objective:To analyse the accuracy of maximum-slope method in the condition of low injection rate and to find out an efficient way to improve its accuracy. Methods:40 cases of healthy adults were divided into two groups at random,contrast medium with 4ml/min and 2ml/min was injected for each group respectively and then bilateral cortex of kidney was scanned with MSCT.Maximum-slope method,improved maximum-slope method and deconvolution arithmetic was used to measure the perfusion parameter of renal cortex respectively,the accuracy of maximum-slope method and improved maximum-slope method was evaluated according to the standard of deconvolution arithmetic (SAS 6.12,F test,α=0.05).Results:The maximum-slope method could underestimate the tissue blood flow under the condition of low injection rate,the lower the injection rate was applied,the higher the extent of underestimation was.There was not significant difference between the improved maximum-slope method and deconvolution arithmetic (P<0.05).Conclusion:The improved maximum-slope method can be used to measure the MSCT tissue perfusion approximately in the condition of low injection rate.