负荷双时相18F-FDGPET／CT心肌显像诊断心肌缺血的实验研究

Experimental study in detection of myocardial ischemia with stress dual-phase 18F-FDG myocardial PET/CT

目的探讨负荷双时相（早期相＋延迟相）18F—FDGPET／CT心肌显像诊断心肌缺血的价值。方法选取中华小型猪10头制作心肌缺血模型，分别进行如下3组显像：造模前负荷双时相显像（8头）、造模后静息双时相显像（8头）和造模后负荷双时相显像（10头）。（造模前、后）负荷双时相显像：实验猪显像前禁食12h以上，全程麻醉，按体质量静脉注射”F—FDG5MBq／kg，静息50win后连续采集PET图像10wi-（早期相）；后经静脉持续泵人多巴酚丁胺，50min后再次采集PET图像10win（延迟相）。造模后静息双时相显像：除未泵人多巴酚丁胺外，余步骤同负荷双时相显像。对显像结果进行分析：（1）定性分析。观察各显像组双时相显像左室心肌18F—FDG摄取情况，分为1～4级。1或2级均判定为无心肌缺血，3或4级中如果存在前壁或间壁局灶性摄取则判定为心肌缺血。利用配对疋。检验分别比较3组显像中早期相与延迟相发生缺血的心肌比例。（2）定量分析。测定左心室前壁和下壁SUVmean。并计算其比值K1利用Wilcoxon秩和检验分析K1（早期相）、K2（延迟相）间的差异。结果造模后CAG显示全部猪LAD冠脉狭窄程度均大于70％。造模前负荷双时相显像：早期相及延迟相中全部8头均为1或2级，判定为心肌缺血的比例均为0；K1、K2间差异无统计学意义（1．08±0．10和1．11±0．10；Z=-1．48，P〉0．05）。造模后静息双时相显像：早期相与延迟相中心肌缺血比例分别为1／8和3／8，差异无统计学意义（x2=0．50，P〉0．05）；K1、K2间差异也无统计学意义（1．47±0．28和1．28±0．40；Z=-2．02，P〉0．05）。造模后负荷双时相显像：早期相与延迟相的心肌缺血比例分别为4／10和10／10，差异有统计学意义（x2=4．17，P〈0．05）；K1、K2间差异也有统计学意义（1．55±0．32和1．86±0．39；Z=-2．49，P〈O．05）。结论负荷双时相18F-FDGPET／CT心肌显像可用于心肌缺血的诊断。

Object（ve To explore the value of stress dual-phase （early and delayed phases）18 F- FDG myocardial PET/CT in detection of myocardial ischemia. Methods Ten swine were prepared as ischemic models and underwent 3 imaging procedures： pre-model stress （8 swine）, post-model rest （8 swine） and post-model stress dual-phase imaging （10 swine）. To perform stress dual-phase imaging, the tested subjects were fasted for more than 12 h and underwent early-phase PET imaging at 50 rain after the intravenous injection of mSF-FDG （5 MBq/kg） for 10 rains, and followed by a dobutamine stress test, and then delayed-phase PET imaging at 50 min after the stress test for another 10 rains. The post-model rest dual-phase imaging was performed in almost the same way except that there was no dobutamine-loading, lSF-FDG uptake image was qualitatively analyzed and classified into 4 levels ： 1 = no uptake, 2 = diffuse uptake, 3 = focal uptake, 4=focal on diffuse uptake. Level 1 or 2 was considered as normal. If the focal uptake （level 3 or 4） was found on anterior wall or septura, ischemia was diagnosed. ^（2 test was used to determine the difference of the rate of ischemic myocardium between the two phases, lSF-FDG uptake ratio of the anterior wall to pos- terior wall （K） of the left ventricle was calculated （K1 for early phase and K2 for delayed phase）. Wilcoxon rank sum test was applied to determine the difference between K1 and K2. Results CAG showed LAD stenosis 〉70% in all swine. In pre-model stress dual-phase imaging, no ischemia was detected at two phases （8/8 for level 1 or 2, 0 for level 3 or 4）.There was no significant difference between K1 and K2（ 1.08±0.10, 1.11±0.10 ; Z = - 1.48, P〉0.05）. In post-model rest dual-phase imaging, the rate of ischemic myocardium was not significantly different between early and delayed phases （ 1/8, 3/8; X2 = 0.50, P〉0.05） .There was no significant difference between K1 and K2（ 1.47±0.28, 1.28±0.40; Z=-2.02,P〉0.05）. In post-model stress dual-phase imaging, the rate of ischemic myocardium between the two phases was statistically different （4/10, lO/lO;XE=4.17,P〈0.05）, and the difference between K1 and K2 was also significant （1.55± 0. 32, 1.86±0.39; Z=-2.49, P〈0.05）. Conclusion Stress dual-phase 18F-FDG myocardial PET/CT might be useful for the diagnosis of ischemia.