正常实验猪心肌灌注成像中伪影探讨

The Endocardial “Dark Rim” Artifact in MRI Myocardial Perfusion Imaging of Normal Pigs

目的:分析正常实验猪MR心肌灌注成像中伪影形成的影响因素,并总结伪影表现。方法:选择11头正常家猪进行静息及潘生丁负荷MR心肌灌注成像检查。所有实验猪均经冠状动脉造影证实无冠状动脉病变。依据心肌节段伪影有无与伪影出现时相(磁敏感度)、心脏收缩运动、相位编码方向及层厚(through-plane空间分辨率)之间的关系进行两分类Binary Logistic回归分析。结果:磁敏感度、心脏收缩运动及相位编码方向三者与心肌灌注成像伪影的形成存在一定关系,其中以磁敏感度影响最大(OR值=5.735)。伪影多出现在心腔信号最强而心肌开始强化的时刻,即受磁敏感度影响,呈一过性表现。层厚与伪影形成关系不大。结论:MR心肌灌注中出现的心内膜下伪影受多种因素影响,以磁敏感度影响最明显。认识该伪影表现对鉴别诊断及半定量分析大有裨益。

Purpose： To analyze causes and appearance of the endocardial ＂dark rim＂ artifact in MR firstpass myocardial perfusion imaging. Methods： First-pass contrast-enhanced MR imaging was performed at rest and after the infusion of dipyridamole in 11 healthy pigs that were proved to be normal in the coronary angiography before MR scans. The association between the band artifact and the influence factors including the susceptibility effect from the gadolinium bolus, cardiac motion, the direction of the phase-encoding （inplane spatial resolution） and slice thickness （through-plane spatial resolution） was analyzed. Binary logistic regression was used to evaluate the relationship of them. Results： The dark rim artifact was due to the combination of susceptibility effect, cardiac motion and in-plane spatial resolution. Among them, the influence of susceptibility effect was the largest, whose OR （odds ratio） was 5.735. The ＂dark rim＂ artifact often raised in tandem with the arrival of the bolus of gadolinium in the left ventricle. It typically preceded myocardial tissue uptake and was transient in nature. However, the effect of slice thickness was limited. Conclusion： The endocardial ＂dark band or rim＂ artifact is due to many factors, while the susceptibility effect plays the dominating role. The recognition of the appearance of the artifact will be helpful for differentiating it from the true perfusion defects.