造影剂超声图像的纹理与心腔内压力相关性研究

用计盒分形模拟分析经静脉注射Levovist声学造影剂后在二次谐波成像方式下的超声图像纹理变化，研究发现左心室区域超声图像的分形维数D和分形辅助特征量C（L）在连续心动周期中具有规律性变化，即分形维数D的最大值出现在舒张末期，最小值出现在收缩末期，随着心室收缩期开始，D值由大变小，而舒张期开始，D值又由小变大；而分形辅助特征得C（L）的最大值出现在收缩末期附近，最小值出现在舒张末期附近，从左室收缩期开始到收缩末期之间C（L）具有由小变大的趋势，舒张期开始到舒张末期之间具有由大变小的趋势。它们的这种变化与左心室内压力的变化情况十分相似，可见造影剂超声图像的分形纹理特征与心腔内压力的变化具有相关性。研究结果表明这种相关性有可能用于无创地测量心腔内压力。

On the Correlation between the Texture of Contrast Agent Ultrasonic Image and the Intracardiac Pressure

Based on the application of box-counting fractal model to the texture analysis of ultrasonic image after intravenous injection of Levovist acoustics contrast agent in a dog, this paper presents a method to calculate the fractal dimension(D) and assistant characteristic(C(L)) of the ultrasonic images of left ventricle. It was found that the D and C(L) changed regularly in the continued cardiac cycles, that is, the maximum value of D appears during diastasis, the minimum value appears during end-systole; as the ventricular systole begins, D changes from maximum to smallness, and as the diastole begins, D changes from smallness to maximum; the maximum value of C(L) appears around end-systole, the minimum value appears around diastasis; from the start of left ventricular systole to end-systole, C(l) shows a tendency to change from smallness to maximum, and from the start of diastole to diastasis, it shows a tendency to change from maximum to smallness. The changes of D and C(L) are very similar to the changes of left ventricular pressure. It is thus evident that there is correlation between the fractal texture characteristics of the contrast agent ultrasonic images and the changes of intracardiac pressure. The results demonstrate that it is possible to measure the intracardiac pressure noninvasively.