Sponheim N, Myhrum M
Nycomed Imaging AS, Clinical R&D, Oslo, Norway.
Ultrasonics. 1996 Jun;34(2-5):599-601. doi: 10.1016/0041-624x(96)00033-9.
Ultrasound contrast agents for vascular use are gas-filled microspheres and will increase the backscatter from blood and therefore enhance the Doppler signal. Studies have shown that Doppler enhancement may result in an increased maximum velocity when observed as the envelope of the spectral Doppler screen. Change in observed velocity may be due to biological or instrumentational effects. The purpose of this study was to investigate the possible instrumentational effects on the Doppler signal after injection of the contrast agent (Infoson). By performing the measurements on a Doppler phantom, the biological effects was eliminated. Computer simulations of limited frequency resolution were compared to measurements. The conclusion was that the increase in detected maximum velocity after Infoson injection is due to the combined effect of signal enhancement and limited frequency resolution. It is shown that a large change in signal strength can change the estimated maximum frequency from the spectral Doppler whether this is due to a contrast agent or instrument settings. It is therefore important in a clinical situation to have an adequate, but not too strong or too weak signal in order to make the best velocity estimates.
用于血管的超声造影剂是充气微球，会增加血液的反向散射，从而增强多普勒信号。研究表明，当作为频谱多普勒屏幕的包络观察时，多普勒增强可能会导致最大速度增加。观察到的速度变化可能是由于生物学或仪器效应。本研究的目的是研究注射造影剂（声诺维）后对多普勒信号可能产生的仪器效应。通过在多普勒体模上进行测量，消除了生物学效应。将有限频率分辨率的计算机模拟与测量结果进行了比较。结论是，注射声诺维后检测到的最大速度增加是信号增强和有限频率分辨率共同作用的结果。结果表明，无论信号强度的大幅变化是由造影剂还是仪器设置引起的，都会改变频谱多普勒估计的最大频率。因此，在临床情况下，拥有足够但不过强或过弱的信号以进行最佳速度估计非常重要。
