MR回顾性门控与心电呼吸触发快速小角度激发序列在心脏结构及功能的应用

The comparison of MR intragate and electrocardiogram-respiration triggered fast low-angle shot in imaging the structure and function of the heart

目的探讨7．0TMR回顾性门控快速小角度激发（FLASH）序列与心电呼吸触发FLASH序列在测量心脏结构及功能方面的差异。方法对10只正常ICR小鼠行MR短轴面多层扫描，并选出位于其中央乳头肌平面进行FLASH—cine亮血、FLASH—cine—Blackblood（黑血）、回顾性门控快速小角度激发饱和电影序列（IG—FLASH—sat—cine黑血）及IG—FLASH—cine亮血序列扫描。在以上电影序列所得图像中，采用手工绘制ROI的办法（测量3次后求平均值）分别测出以上每个序列收缩末期及舒张末期小鼠的左心室面积，并分别求出该层面上心肌增厚的面积及心腔由收缩末期到舒张末期所增加的面积；并从心脏收缩末期图像的左心室心肌等分的位置取8个ROI，分别测出其心肌信号强度，求出其x^-±s，并得出变异系数值，并对以上测出的左心室心肌增厚面积、心腔增加面积及心肌8个ROI信号强度的变异系数值用配对t检验法进行统计分析。结果自触发的黑血序列所得心脏功能参数[心肌增厚面积（0．090±0．014）cm^2，心腔增加的面积（0．060±0．012）cm^2]与采用心电呼吸触发的黑血序列所得心脏功能参数[心肌增厚面积（0．100±0．018）cm^2，心腔增加的面积（0．06±0．024）cm^2]之间差异无统计学意义（心肌增厚面积t=0，P=1，心室增加的面积t=2．12，P=0．06），自触发的亮血序列所得心脏功能参数[心肌增厚面积（0．090±0．019）cm^2，心腔增加的面积（0．050±0．015）cm^2]与采用心电呼吸触发的亮血序列所得心脏功能参数[（0．100±0．018）cm。，心腔增加的面积（0．060±0．014）cm^2]间差异也无统计学意义（心肌增厚面积t值分别为1．56、2．08，P值分别为0．15、0．07），自触发的亮血序列所得心肌信号变异系数值（0．040±0．015）与采用心电呼吸触发的亮血序列所得心肌信号变异系数值（0．050±0．013）之间比较差异没有统计学意义（t=1，P=0．34），但自触发的黑血序列所得心肌信号变异系数值（0．160±0．046）与采用心电呼吸触发的黑血序列所得心肌信号变异系数值（0．070±0．033）之间比较差异存在统计学意义（t=4．51，P=0．001）。结论自触发的心脏序列可以代替心电呼吸触发序列做心脏功能方面的分析，也可使用自触发的亮血序列代替心电呼吸触发的亮血序列来分析心肌信号。

Objective A comparison between intragate and ECG-respiration triggered techniques was performed to determine their differences in measuring the structure and function of the heart at 7.0 T. Methods Ten normal ICR mice aged five to six weeks were examined on a 7.0 T MR scanner. A central slice with papillary muscle included at the short-axis view was scanned with a FLASH-cine bright blood sequence,FLASH-cine black blood sequence, IG-FLASH-sat-cine black blood sequence, and IG-FLASH- cine bright blood sequence. The area of the left ventricle of the end systole and end diastole （including and excluding the myocardium） was measured with manually outlined ROIs. The increased area of the left ventricle and the myocardium from the end systolic to end diastolic phases was calculated. The signal intensity was measured from 8 ROIs which were evenly located at the myocardium of the end systole, and the mean and standard deviation were then determined. The coefficient of variation （CV） was derived by dividing the mean into the standard deviation. Results There was no significant difference （the increased area of the myocardium t = 0, P = 1, the increased area of the left ventricle t = 2. 12,P = 0. 06） in the function index between the ECG-triggered black blood sequences [ the increased area of the myocardium （0. 100 ± 0. 018） cm^2,tbe increased area of the left ventricle （0. 060 ± 0. 024） cm^2] and intragate black blood sequences[ the inereased area of the myoeardium （0. 090± 0. 014） cm^2, the inereased area of the left ventricle （0, 060 ±0. 012） cm^2]. No significant differenee（ the inereased area of the myocardium t = 1.56, P = 0. 15, the increased area of the left ventricle t = 2.08, P = 0. 07 ） in the function index was observed between the ECG-triggered bright blood sequences [ the inereased area of the myoeardium （ 0. 100 ± 0. 018 ） cm^2, the increased area of the left ventricle （0. 060 ± 0. 014 ） cm^2] and intragate bright blood sequences [ the increased area of the myocardium （0. 090 ±0. 019） cm^2 ,the increased area of the left ventricle （0. 050 ± 0. 015） cm^2]. Furthermore, there was no significant difference（t = 1 ,P = 0. 34）in the CV of the myocardium signal intensity of bright blood sequences between the ECG-triggering （ 0. 050 ± 0. 013 ） and intragate （0. 040 ± 0. 015 ）, but significant difference （t = 4. 51, P = 0. 001 ）in the CV of the myoeardimn signal intensity of black blood sequences between the ECG-triggering （ 0. 070 ± 0. 033 ） and intragate （ 0. 160 ± 0. 046 ） was obtained. Conclusions The intragate sequences eould take the place of the ECG gate sequences in functional analysis of the heart（ including bright blood and black blood sequences）. The bright blood intragate sequences also could replaee the bright blood ECG-triggered sequences in analyzing the signal of the myocardium.