心脏磁共振T1 mapping在评估狗心肌梗死中的作用

Evaluation of cardiac magnetic resonance T1 mapping in myocardial infarction of canine

目的探讨T1mapping检测心肌梗死对梗死类型、梗死分期及磁场强度的依赖性。方法建立24只狗的心肌梗死模型(MI),其中出血性心梗(n=15)和非出血性心梗(n=9)。分别在MI的急性和慢性期对全部受试动物进行多参数mapping(T1和T2~*)和晚期钆增强(LGE)扫描。比较不同时期及不同场强下出血梗死区、血肿周围梗死区、非出血性梗死区和非梗塞区(远端心肌)的T1和T2~*值。结果出血性梗死区在急性期和慢性期、1.5T或3.0T均表现为显著的T2~*减低(P<0.005)。而梗死区域的平扫T1及其与远端心肌的相对变化显示出对梗塞分期、类型和磁场强度的显着依赖性,急性期各梗死区以及慢性期的血肿周围梗死区和非出血性梗死区在1.5T及3.0T的T1map上均表现出相对远端心肌的高信号(P<0.005)。在MI的慢性期,出血性梗死区域的T1在1.5T下低于远端心肌水平(T1%=-9.8±8.6%,P<0.005),然而,在3.0T下出血性梗死区域的的T1相对于远端心肌并无显著差异(T1%=-0.6±6.6%,P=0.634)。结论非出血性心梗及急性期出血性心梗依赖T1与正常心肌鉴别,但慢性期出血性心梗的鉴别需要联合T2~*对梗死区域进行空间定位。

Objective To investigate dependence of T1 mapping detecting myocardial infarctions(MI) on infarct stage, infarct type and magnetic field strength. Methods Multi-parametric non-contrast mapping(T1, T2 and T2~*) and late-gadolinium enhancement(LGE) were performed in the acute and chronic phases of hemorrhagic(n=15) and nonhemorrhagic(n=9) MI canines. T1 and T2~* values of the hemorrhagic, infarcted areas surrounding the hemorrhage(perihemorrhagic), non-hemorrhagic and un-infarcted/remote territories were measured. The changes in T1 and T2~* between the MI territories from remote myocardium were compared respect to infarct age and field strength. Results T2~* in acute or chronic phases was significantly lower in hemorrhagic area than in remote myocardium,while native T1 of MI territories and their relative change from remote myocardium showed significant dependence on infarct age and type. Specifically, all infarct territories in acute phase of MI as well as peri-hemorrhage and non-hemorrhagic territories in chronic phase of MI showed the elevated T1 relative to remote myocardium. T1 of hemorrhagic territories showed significantly lower in chronic phase of MI than in remote myocardium at 1.5 T(T1%=-9.8±8.6%, P<0.005), but with no difference with that in remote myocardium at 3.0 T(T1%=-0.6±6.6%, P=0.634). Conclusion Non-hemorrhagic MI and acute hemorrhagic MI were differentiated from normal myocardium using native T1 mapping, but the identification of chronic hemorrhagic MI requires T2~* to spatially localize the infarcted area.