T1 mapping定量技术在慢性心肌缺血模型猪的初步应用研究

Quantification of myocardial T1 mapping in minipig with chronic myocardial ischemia

目的采用心脏磁共振T1 mapping技术,检测正常猪及其在慢性心肌缺血造模后的心肌T1定量值,为心肌缺血诊断提供新的定量参数,探索T1mapping技术分析判断慢性心肌缺血或梗死的可行性。材料与方法选取13只中华小型猪,于冠脉左前降支近中段手术植入蛋白缩窄环,4 w后建成慢性心肌缺血小型猪模型;于造模前后行3.0 T心脏磁共振扫描(cardiac magnetic resonance,CMR),在短轴位的心尖、乳头肌水平层面行T1 mapping扫描,分别在增强前后测定左心室壁感兴趣区的心肌T1定量值,应用独立样本t检验,统计分析比较造模前后、增强前后T1值的差异。结果 12只正常猪完成了造模前磁共振检查,所有层面平扫心肌平均T1值为(1108.9±10.5)ms,其中心尖部心肌平均T1值为(1050.2±16.7)ms,乳头肌层心肌平均T1值为(1139.7±54.4)ms,两个层面平均T1值差异有统计学意义(P<0.05);11只慢性心肌缺血模型猪完成了CMR扫描,心尖部心肌平均T1值为(1210.6±94.2)ms,比造模前升高,差异有统计学意义(P<0.05);乳头肌层心肌平均T1值为(1236.0±114.3)ms,与造模前差异无统计学意义(P>0.05);但是,乳头肌层的前壁、前间壁与其造模前后的平均T1 mapping的差异具有统计学意义(P值分别为0.017和0.006)。结论左室前壁、前间壁为前降支供血区,T1 mapping在造模前后差异具有统计学意义(P<0.05),因此,此技术对诊断心肌慢性缺血或梗死有定量参考价值。

Objective： The purpose of this study is to quantify the myocardial T1 mapping values in minipig modelling for chronic myocardial ischemia. Materials and Methods： The minipigs were implanted the protein constriction ring（Ameroid） at left anterior descending artery to induce ischemia. The minipigs were scanned twice in a 3.0 T MRI scanner at the short axial slices of the apex, the papillary muscle, at the time of the baseline of the normal heart and at the 4th week after the operation with the chronic myocardial ischemia. The independent-samples t test was employed to analyze the difference of the T1 mapping values of the heart muscles between the two conditions. Results： In this study, 12 minipigs completed CMRI scan before modeling, The unenhanced myocardial average T1 values was（1108.9±10.5） ms, the mean myocardialT1 values were（1050.2±16.7） ms and（1139.7±54.4） ms respectively at the apex and papillary muscle myocardium, the difference was statistically significant. There were 11 minipigs completed CMR scan after modeling, the apical myocardial average T1 values was（1210.6±94.2） ms, it was higher than baseline, the difference was statistically significant. The mean myocardial T1 value of the papillary muscle was（1236.0±114.3） ms at chronic ischemia minipigs, no significant difference with baseline. Furthermore, statistically significant differences existed in the anterior and anteroseptal of the papillary muscle. Conclusion： The T1 mapping technique is valuable as a new important index for the diagnosis of chronic ischemic myocardium.