基于7．0TMR扩散张量成像显示正常大鼠离体心肌纤维特性

The research of myocardial fibers character in isolated rats heart based on 7.0 T diffusion tensor imaging

目的采用7．0TMR扩散张量成像（DTI）技术从心肌水分子扩散、心肌纤维微结构及心肌力学单元角度综合定量评价正常大鼠心肌纤维特性。方法10只雄性sD大鼠心脏离体、固定后采用DTI技术获取图像，并利用DiffusionToolkit及Matlab软件进行图像后处理，观察心肌纤维整体排布及走行，测量各向异性分数（FA）值、ADC值、纤维长度、纤维密度、左心室平均螺旋角，采用单因素方差分析统计心外膜与心内膜的前壁、室间隔、侧壁及后壁的平均螺旋角的差异。结果定性分析发现，SD大鼠心肌纤维由心外膜向心内膜呈致密、规则的螺旋排布；与同层面HE染色对比，乳头肌层面心肌纤维示踪图以及张量图显示心肌纤维走行规则、排布均匀。定量分析发现，正常SD大鼠心肌ADC值为（9．6±3．6） ×10^-4mm^2／s，FA值为0．80-±0．04，纤维密度为（981±24）track／mm^3，纤维长度为（6．18±1．71）mm。左心室心肌纤维由心外膜至心内膜的平均螺旋角透壁范围从-81．37°至0°再至82．83°逐渐过渡，乳头肌层面的心外膜与心内膜前壁、室间隔、侧壁及后壁的平均螺旋角差异均无统计学意义沪值均〉0．05）。结论DTI技术可从心肌水分子扩散、微结构以及力学角度综合定量评价正常大鼠心肌纤维特性。该研究为评价心肌疾病模型大鼠心肌纤维特性提供前期的实验基础及有力的技术支持。

Objective Using 7.0 T diffusion tensor imaging（DTI） to study myocardial fibers character in isolated rats heart in aspect of water molecular diffusion, myocardial mechanics and mierostructure. Methods Fixed male rats heart （n=10） underwent DTI and the myocardial structures were quantitatively measured by Diffusion Toolkit and Matlab. The characteristic of myocardial fibers arrangement was observed and FA values and ADC values of myocardial fibers, myocardial fibers density and length, mean helix angle of left ventrieular were calculated as well. Mean helix angle of anterior wall, ventricular septum, lateral wall and posterior wall of epieardium and endocardium were compared by using one-way ANOVA. Results The SD rats＇ myocardial fibers appeared in compact and inerratie distribution from epicardium to endocardium. Compared with HE staining, regular direction and arrangement in fibers were showed in myocardial fibers tracer map and tensor map in papillary muscle plane. Quantitative analysis showed that ADC value of SD rats＇ myocardial fibers was （9.6±3.6）×10^-4mm^2/s, FA value was 0.80±0.04, myocardial fibers density was （981±24） tracks/mm^3 and myocardial fibers length was （6.18±1.71）ram. Mean helix angle of left ventricular epieardium to endocardium ranged from- 81.37° to 0° and then gradually change to 82.83° There were no significant differences in mean helix angle of anterior wall, ventrieular septum, lateral wall and posterior wall of epieardium and endocardium, respectively （F=2.25, 0.40, P〉0.05）.Conclusions This study shows that DTI is an effective method to quantitatively measure the characteristics of myocardial fibers. This study provides useful information for further study of myocardial fibers in heart disease models.