Mor-Avi V, Akselrod S, David D, Keselbrener L, Bitton Y
Medical Physics Laboratory, School of Physics, Tel Aviv University, Israel.
Ultrasound Med Biol. 1993;19(8):635-48. doi: 10.1016/0301-5629(93)90070-5.
The mean transit time of a tracer through a sample of tissue is a quantitative marker most closely related to regional tissue blood flow. Therefore, an accurate estimation of the mean time of transit of an ultrasonic tracer through a sample of myocardial tissue, obtained by contrast echocardiography, may provide a quantitative noninvasive estimate of myocardial perfusion. We hereby present an algorithm for the determination of the mean transit time by computerized analysis of a series of contrast-enhanced echocardiographic images. The algorithm comprises the evaluation of the echocardiographic impulse response function of a selected region of interest, using a deconvolution technique based on a fast Fourier transform and a frequency domain division of the videointensities measured in the sample, by that measured in a predetermined reference region. An extensive computer simulation study was designed to facilitate the optimization of the steps of analysis. We present the results of the evaluation study performed in order to assess the accuracy of the procedure in computer-simulated echocardiographic images. Within a wide range of parameters chosen to define these functions, the analysis is shown to be essentially independent of the rise and decay times of the impulse response function of the tissue sample as well as of the simulated intensities. The effects of random noise introduced into the simulated intensity curves and of their variable width were investigated. The mean transit time was found to be accurately evaluated within about 10% of error for the variety of widths and noise levels permitted. The reconvolution error did not correlate with the accuracy of the evaluation of the mean transit time, indicating that the reconvolution error cannot be used as an estimate of the accuracy of the procedure. The numerical methods and the results of the computer study are discussed in detail. The approach is proposed to be used as part of a more general technique for the quantitative measurement of regional myocardial tissue blood flow.
示踪剂通过组织样本的平均通过时间是与局部组织血流最密切相关的定量指标。因此，通过对比超声心动图获得的超声示踪剂通过心肌组织样本的平均通过时间的准确估计，可能提供心肌灌注的定量无创估计。我们在此提出一种通过对一系列对比增强超声心动图图像进行计算机分析来确定平均通过时间的算法。该算法包括使用基于快速傅里叶变换的反卷积技术和对样本中测量的视频强度与在预定参考区域中测量的视频强度进行频域划分，来评估感兴趣选定区域的超声心动图脉冲响应函数。设计了一项广泛的计算机模拟研究，以促进分析步骤的优化。我们展示了为评估该程序在计算机模拟超声心动图图像中的准确性而进行的评估研究结果。在所选择的用于定义这些函数的广泛参数范围内，分析显示基本上与组织样本脉冲响应函数的上升和衰减时间以及模拟强度无关。研究了引入到模拟强度曲线中的随机噪声及其可变宽度的影响。对于所允许的各种宽度和噪声水平，发现平均通过时间在约10%的误差范围内得到准确评估。反卷积误差与平均通过时间评估的准确性不相关，这表明反卷积误差不能用作该程序准确性的估计。详细讨论了数值方法和计算机研究结果。该方法被提议用作更通用的局部心肌组织血流定量测量技术的一部分。
