Experimental Evaluation on Normal Cardiac Perfusion of Dogs by Using Harmonic Doppler Imtermittent Ultrasound Imaging Combined with Myocardial Contrast Echocardiography

ABSTRACT Objective: To observe the normal cardiac perfusion and myocardial contrast, evaluate the myocardial contrast echocardiography on the anisotropic properties of myocardial tissue.

Methods:Twelve dogs were performed with intravenous infusion of perfluorocarbon gas (C3F8)contrast agent by using Doppler tissue energy imaging(DTE), second harmonic imaging (SHI), and intermittent ultrasound imaging (IUI). The pixel video intensity(PVI) and the abstraction value of left ventricle after and before using contrast was computed.

Results: The PVI of normal cardiac muscle and myocardial contrast of each regional left ventricular walls was anisotropic, and significant different (P<0.001). The difference of PVI after and before myocardial contrast of each regional left ventricular walls was also anisotropic. In that with significant difference (P<0.001). This kind of difference of PVI in normal cardiac muscles was over 35 PVI units.

Conclusions:The PVI of normal cardiac muscle and myocardial contrast of different regional left ventricular walls is evidently different,which is caused by the structure of cardiac muscle and ultra-sonic imaging techniques. MCE can sensitively and accurately determine the whole process of normal cardiac perfusion.

KEY WORDS  Myocardial contrast echocardiography  Harmonic Doppler tissue energy imaging  Normal cardiac perfusion

本研究应用本室自制氟碳造影剂结合多普勒组织能量成像对犬正常心肌血流灌注进行造影观察并深入分析各部位心肌的彩色象素视频密度(Pixel Video Intensity, PVI)值及其相关影响因素。

资料与方法

1.实验动物:健康杂种犬12条(由北京军区总医院动物室提供),体重10.5~15kg,雌雄不限,其中雌性4条、雄性8条。3%戊巴比妥钠1ml/kg体重肌注麻醉,气管插管,连接呼气末正压电动呼吸机(MOD-EL SC-3电动呼吸机,上海医疗设备厂),呼吸比为1∶2,潮气量400ml。连接心电图。左股静脉插入扩张管套鞘用于静脉注射超声造影剂。于左侧4~5肋间开胸,充分暴露心脏,打开心包壁层,用丝线将心包壁层悬吊起来,缝于胸壁上,使心脏卧于心包吊床上。

2.造影剂:按Poter文献报道方法^[1],自行制备:5%人血清白蛋白(由重庆健新血液制品有限公司提供)和6%低分子右旋糖酐(由石家庄制药集团有限公司提供)按1∶3的体积比混合,置于注射器内,固定于声振仪探头中。声振仪(SONICATOR XL2020,Misonix Incorporated, USA)的输出功率165Watts/cm²,声振时间为120秒,声振频率为20kHz。声振时由注射器下端推入纯净氟碳气体(PerfluorocarbonGas PFC, C3F8,由核工业总公司特种气体研究所提供,纯度99%)。停止声振后静置数分钟,液体分为上下两层,上层为乳白色细腻微泡沫,为所需造影剂。经血球计数板及Coulter计数器检测,其浓度为5.4±1.8×10⁸/ml,微泡直径为4.8±2.7μm,PH值6.0。造影剂制做重复性良好。

3.超声仪器:彩色超声诊断仪Sequioa 512 (Acuson公司) 5.07版本, 3V2C 1.75/3.5MHz二次谐波变频电子相控阵探头,具有DTI功能,置于水囊上,显示左室乳头肌水平短轴切面。探头的位置和角度在实验过程中保持不变。调节仪器各种参数以获得最佳图像。彩阶速度为0.69m/s,帧频65Hz,输出能量0dB,彩色多普勒机械指数(Micd) 1.9,软组织表面热量指数(TIS) 1.6,彩色增益42dB, DTE增益65dB。

4.实验方案:采用自身前后对照研究。静脉心肌造影采用二次谐波成像(SHI) +间歇式超声成像(IUI) +彩色多普勒组织能量成像(DTEI)技术,心电图触发间隔为3个心动周期。造影剂注射方式采用外周静脉弹丸式注射,剂量为0.05ml/kg体重,分别肌各节段彩色象素视频密度值,如表2所示。左室8个心肌节段造影后心肌彩色象素视频密度(PVI)值之间经SAS统计学处理,造影前后彩色象素视频密度(PVI)值之间均有着显著差异(F=4.84,P=0.0001)。