Estimation of Regional Myocardial Blood Flow by Trans Venous Micro-bubble and Two Dimensional Low Frequency Doppler

为了利用微泡的非线性特性进行组织灌注的超声可视化，在Albunex、SHU 508 A、QW 3600和F-04 E（PVC-AN）四种超声造影剂上研究了微泡的基本特性。用12位A/D转换器将微泡后向散射的射频信号或/和多普勒信号数字化。计算了射频功率谱和多普勒频移。用2.5和3.5MHz扫描仪进行B型扫描或用2.0和2.5MHz探头和可变脉冲重复率进行多普勒采样。观察到功率谱和基波/二次谐波比的衰减。数字化射频信号进行希尔伯特变换与傅里叶变换和频率带通滤波载波（基波）和二次谐波。从Hilbelt变换得到的反映局部后向散射振幅的B型图像中，选择微泡区域。随着连续扫描，以dB为单位的反向散射幅度呈指数下降。在2.5MHz扫描下，Albunex的背向散射衰减最大。SHU 508 A和F-04 E表现出类似的指数衰减，但速度较小。在所有微泡中，2.5MHz的绝对背向散射和二次谐波/基波的比值（.186至.371）大于3.5MHz。在2.5MHz时衰减也较大。与其他三个气泡相比，QW 3600显示出相当缓慢的反向散射衰减，具有对超声暴露的耐久性。在2.5MHz下，Albunex的载波频率和二次谐波的衰减是不一致的。

To utilize non-linear character of micro-bubbles for ultrasonic visualization of tissue perfusion, fundamental characters of micro-bubbles were studied on Albunex, SHU508A,QW3600 and F-04E (PVC-AN). Radio-frequency (RF) signals of backscatter from micro-bubbles or/and Doppler signal were digitized with 12bit A/D converter. Power spectra of RF and Doppler shift were calculated. B-mode scan with 2.5 and 3.5MHz scanner or doppler sampling with 2.0 and 2.5MHz probe and variable pulse repetition rates were performed. Decay of power spectra and fundamental/second harmonic ratio were observed. Digitized RF signal were Hilbert transformed with Fourier transformation and frequency band-pass filtering to carrier (fundamental) and 2nd harmonic. From B-mode image representing regional amplitude of back scatter obtained with Hilbelt transform, the region of micro-bubble was selected. The amplitude of back scatter in dB was exponentially decreased with continuous scan. The decay of backscatter was the largest in Albunex under 2.5MHz scan. SHU508A and F-04E showed similar exponential decay with smaller velocity. In all micro-bubbles, the absolute backscatter and the ratio of the second harmonic/fundamental (.186 to .371) were larger in 2.5MHz than in 3.5MHz. The decay was also larger in 2.5MHz. QW3600 showed quite slow decay of backscatter with durability to ultrasound exposure, compared to the other three bubbles. The decay of carrier frequency and 2nd harmonic was not identical in Albunex under 2.5MHz.