磁共振延迟成像时间对急性心肌梗死测定的影响

Effect of imaging time on infarct size estimation after acute myocardial infarction using delayed contrastenhancement magnetic resonance imaging

目的本研究探讨不间磁共振延迟成像（conlrast—enhanced magnetic resonance imaging，CeM—RI）时间是否影响急性心肌梗死（acute myoeadial infaretin，AMI）后梗死面积的测定。并探讨磁共振测定的射血分数与左室造影测定的射血分数的相关性。方法选择在2005年6月至2006年4月在复旦大学附属中山医院住院治疗的患者，27例首次确诊为急性心肌梗死的患者进行前瞻性研究，年龄（54．3±10．5）岁。所有患者均动态观察心肌酶谱的变化，并经冠脉造影明确，冠脉造影同时测定左室造影射血分数，磁共振（SIMENS1．ST）检查时间为心肌梗死后（13．2±5．2）d，磁共振检查方法是首先进行电影扫描，测定射血分数，然后经静脉以5mL/秒注入0．05mmol/kg Gd—DTPA行首过成像，最后经高压注射器静脉以2mL/s注入0．15mmol／kgGd—DTPA行延迟成像，测定心肌梗死面积，在延迟注药后5min开始延迟期采集。选择存在延迟增强高信号区的同一短轴层面，每间隔5min成像一次测定梗死面积，直至20min。采用配对t检验进行统计，并进行相关分析。结果27例患者在延迟CeMRI上均存在延迟增强区，27例患者测定的梗死面积为（17．9±9．8）％，测定CK峰值为（2003．5±1496．8）U／L，肌钙蛋白T峰值为（4．6±3．3）ng／mL。梗死面积与cK峰值的相关系数为r=0．819（P〈0．01），梗死面积与肌钙蛋白丁相关系数为r=0．517（P〈0．05）。存在梗死心肌的同一层面测定的梗死面积百分比在5min，10min，15min及20min时分别为（7．2±6．2）％，（8．5±7．4）％，（7．3±6．3）％及（6．9±6．4）％（10min与20min相比，P〈0．05）：MR测定的左室射血分数与造影测定的射血分数相关系数为r=0．867（P〈0．01）。结论CeMRI可以诊断心肌梗死和定量测定梗死范围。磁共振测定与左室造影测定的射血分数密切相关。测定梗死范围时，不同延迟成像的时问影响梗死范围的测定。

Objective To investigate whether timing of image acquisition influenced infarct size estimation using delayed CeMRI, and the association of left ventricular ejection fraction between magnetic resonance imaging and left ventriealography was also studied. Method From Junary 2005 to April 2006, 27 first, onset AMI patients [ 23 male, mean age（54.3± 10.5） years ] were enrolled in this study. All patients received left ventriculography as well as coronary angiography. The average checking time was （13.2 ±5.2） days after the onset of AMI. MR imaging was performed with a 1.5-T magnet（SIMENS）. After breath-hold cine images were acquired, patients received an intravenous bolus of 0.05 mmol/kg Gd-DTPA at a rate of 5 mL/s. A first-pass perfusion scan was acquired. Then a second bolus of 0.15 mmol/kg Gd-DTPA was given at a rate of 2 mL/s. After the hyperenhance- ment localized, the typical short axis slice with hyperenhancement was chosen to repeat imaging for measuring in- farct size every 5 minutes from 5 minutes after second injection of contrast until 20 minutes. Results Twexty-seren patients showed hyperenhancement at the delayed CeMRI and hypoenhancement at the first pass enhancement （FPE）. The average infarct size estimated by CeMRI was （17.9± 9.8）% of LV mass. Myocardial enhancement at a representative short-axis slice was （7.2 ± 6.2） % of LV mass at 5 minutes, （8.5 ± 7.4） % at 10 minutes, （7.3 ± 6.3） % at 15 minutes and （6.9 ±6.4） % at 20 minutes respectively. There was significant difference between 10-minutes and 20-minutes enhancement size （P 〈 0.05）. Correlations of EF obtained by cineventriculography and MR imaging were significant （ r = 0.867, P 〈 0.01 ）. There were also correlations between infarction size and peak CK （ r = 0.819, P 〈 0.01）, as well as peak cTNT （ r = 0.517, P 〈 0.05） levels. Conclusions Timing of image acquisition influenced infarct size quantification using delayed CeMRI when TI was kept constant.