Ultrasonic tissue characterization of the mouse myocardium: Successful in vivo cyclic variation measurements
Ultrasonic tissue characterization of the mouse myocardium: Successful in vivo cyclic variation measurements
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DOI：
10.1016/j.echo.2004.04.035
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发表时间：
2004-08-01
影响因子：
6.5
通讯作者：
Miller, JG
中科院分区：
文献类型：
--
作者：
Kovacs, A;Courtois, MR;Miller, JG
背景在心脏周期（周期性变化）期间，测量心肌背向散射超声能量的系统变化已成功用于表征大型动物模型和人类受试者中的广泛心脏病理。本研究的目的是评估将循环变异测量扩展到心脏病基因操作小鼠模型研究的可行性，作为进一步深入了解心肌疾病改变特性及其超声表征的方法。方法：在轻度麻醉下，使用具有15- 20 nm的商业成像系统在9只野生型小鼠中获得心脏的胸骨旁长轴图像。MHz标称中心频率线性阵列。对于一系列特定动态范围设置中的每一个，获得一系列特定接收器增益的组织模拟体模和小鼠心脏的图像。这些数据的分析形成了灰度图像校准的基础。通过确定在4个心动周期期间采集的每帧的后壁中层心肌中放置的感兴趣区域的平均灰度值，并使用确定的校准将这些平均灰度值转换为以分贝表示的反向散射值，来获得周期变化测量值。结果表示在周期变化的幅度和时间延迟。为了评估这些测量的重复性，同一组小鼠在第一次研究后2周进行相同的成像方案。结果：发现循环变化的平均幅度为4.6 +/- 0.2 dB，相应的归一化时间延迟为1.02 +/- 0.03，数据平均在所有动态范围设置。使用每种动态范围设置获得的结果之间无显著差异。这些结果与最初研究后2周获得的数据进行比较，结果显示无显著差异。结论本研究首次报道了小鼠周期变异的测量结果，并表明可以在单个动物和不同时间点获得可靠的周期变异测量结果，因此，形成了后续研究的基础，解决了特定的心脏病理和心肌各向异性引起的影响。
Background. Measurements of the systematic variation of backscattered ultrasonic energy from myocardium during the heart cycle (cyclic variation) have been successfully used to characterize a wide spectrum of cardiac pathologies in large animal models and human subjects. The purpose of this study was to evaluate the feasibility of extending cyclic variation measurements to the study of genetically manipulated mouse models of cardiac diseases as a method for developing further insights into the disease-altered properties of the myocardium and its characterization with ultrasound.Methods: Parasternal long-axis images of the heart were obtained in 9 wild-type mice under light anesthesia using a commercial imaging system with a 15-MHz nominal center frequency linear array. Images of a tissue-mimicking phantom and the mouse hearts were obtained for a series of specific receiver gains for each of a series of specific dynamic range settings. Analyses of these data formed the basis for gray-scale image calibration. Cyclic variation measurements were obtained by determining the average gray-scale value for a region of interest placed in the midmyocardium of the posterior wall for each frame acquired during 4 cardiac cycles and converting these mean gray-scale values to backscatter values expressed in decibels using the determined calibration. Results are expressed in terms of the magnitude and time delay of cyclic variation. To evaluate repeatability of these measurements the same group of mice underwent the identical imaging protocol 2 weeks after the first study.Results: The mean magnitude of cyclic variation was found to be 4.6 +/- 0.2 dB with a corresponding normalized time delay of 1.02 +/- 0.03 for data averaged over all dynamic range settings. There was no significant difference among results obtained with each of the dynamic range settings. A comparison of these results with those from data acquired 2 weeks after the initial study showed no significant difference.Conclusions This study represents the first reported measurement of cyclic variation in mice and demonstrates that reliable cyclic variation measurements can be obtained among individual animals and over different time points and, hence, forms the basis for subsequent investigations addressing specific cardiac pathologies and effects arising from myocardial anisotropy.