Vandenberg B F, Melton H E
Cardiovascular Center, College of Medicine, University of Iowa, Iowa City 52242.
J Am Soc Echocardiogr. 1994 Nov-Dec;7(6):582-9. doi: 10.1016/s0894-7317(14)80080-1.
The sonication of human serum albumin produces air-filled microspheres that are used in echocardiographic studies of myocardial perfusion. Recent studies suggest that the microspheres disappear when high pressures are applied, altering the relationship between the administered microsphere dose and the echocardiographic response. Because an ultrasound pulse generates a pressure wave in insonified medium, we hypothesized that with increasing acoustic pulse pressure, the microsphere concentration decreases, hence ultrasonic backscatter decreases. We measured relative integrated backscatter from albumin microspheres diluted in normal saline solution (6152 microspheres/ml) and 5% human plasma protein fraction (24,608 microspheres/ml), with increasing acoustic pulse pressures at the transducer's focus. Backscatter was also measured in normal saline solution with increasing concentrations (up to 15,380 microspheres/ml) of albumin microspheres at an acoustic pulse pressure of 0.11 MPa (1.1 atm). Backscatter and microsphere concentration were related logarithmically: y = 3.38 x 0.32; r = 0.93. Backscatter was unchanged over time at acoustic pulse (peak compression) pressures less than 0.15 MPa (1.5 atm). However, backscatter decreased readily at acoustic pulse pressures greater than 0.33 MPa (3.3 atm), which included any mixing effects. Thus, albumin microspheres are acoustically labile.
人血清白蛋白的超声处理会产生充满空气的微球，这些微球用于心肌灌注的超声心动图研究。最近的研究表明，当施加高压时微球会消失，从而改变了所给药的微球剂量与超声心动图反应之间的关系。由于超声脉冲会在被照射的介质中产生压力波，我们推测随着声脉冲压力的增加，微球浓度会降低，因此超声后向散射也会降低。我们在换能器焦点处，随着声脉冲压力的增加，测量了稀释于生理盐水溶液（6152个微球/毫升）和5%人血浆蛋白组分（24,608个微球/毫升）中的白蛋白微球的相对积分后向散射。还在声脉冲压力为0.11兆帕（1.1个大气压）时，随着白蛋白微球浓度增加（高达15,380个微球/毫升），测量了生理盐水中的后向散射。后向散射与微球浓度呈对数关系：y = 3.38 x 0.32；r = 0.93。在声脉冲（峰值压缩）压力小于0.15兆帕（1.5个大气压）时，后向散射随时间保持不变。然而，在声脉冲压力大于0.33兆帕（3.3个大气压）时，后向散射很容易降低，这其中包括任何混合效应。因此，白蛋白微球在声学上是不稳定的。
