Microbubbles - used as contrast agents in ultrasound imaging - are important tools in biomedical research, having been used together with ultrasound to develop significant diagnostic and therapeutic techniques. It has been suggested that the dynamic behaviour of microbubbles is dependent on the surrounding fluid's ambient (hydrostatic) pressure, and the potential to non-invasively determine blood pressure has numerous medical applications. To study this dependence, a computational mathematical model was created based on Marmottant's dynamic model of a microbubble. A pulse inversion (PI) protocol was incorporated into the model to emphasize the nonlinear behaviour of the microbubble's response. The mathematical model was also used to assess the sensitivity of the microbubbles to undesirable changes in parameters other than the ambient pressure. It found that a variation in the microbubble's initial radius and surface tension would cause the most significant changes in signal energy and hence pose a risk to ambient pressure measurements. To test the practicality of detecting a change in the dynamic behaviour of microbubbles, in vitro experiments were designed and carried out using clinically available contrast agent with two different ultrasound systems. The experiments, while possessing certain limitations, confirmed that there is a change in microbubbles' dynamic behaviour when the ambient pressure is varied, in cases by as little as 7.36 mmHg (981 Pa - a 0.98% change in atmospheric pressure). The experimental results establish a proof-of-principle that future experimental work can build upon to verify the mathematical model, and hence aid in developing a non-invasive blood pressure measurement procedure.
翻译:在超声成像中用作对比剂的微泡泡是生物医学研究的重要工具,与超声波一起用于开发重要的诊断和治疗技术。建议微泡的动态行为取决于周围流体的环境(静水)压力,非侵入性确定血压的潜力有许多医学应用。研究这一依赖性,根据Marmotant的微振动模型微振动压力测量,创建了一个计算数学模型。在模型中纳入了脉冲转换(PI)协议,以强调微泡流反应的非线性行为。数学模型还用来评估微泡对环境压力以外的参数的不可取变化的敏感性。它发现微泡泡最初半径和表面紧张的变异会给信号能量带来最大的变化,从而给环境压力测量的模型带来风险。测试微泡反应(PI)的脉冲转换(PI)协议在模型中强调微泡流的非线性行为,微泡泡泡反应反应反应反应反应反应反应反应的非线性行为。数学模型还用来评估微泡泡泡的动态呼吸器的非线性行为。数学模型还用来评估微泡泡泡泡泡泡泡泡泡泡体对环境温度反应反应的反应,在临床温度测量上进行实验中,在临床上进行某种实验中, 实验中进行某种实验时,在进行某种磁力变变变变变压的实验,在实验中进行某种的实验时,在实验中进行某种变压压的实验中进行某种变变变变变压的实验, 实验,在实验中进行某种变压的实验中, 具有某种变变的实验性反应是具有某种变变变变的实验性反应, 具有某种变的实验性反应,在实验性反应,在实验性反应,在实验,在实验,在实验中进行一种变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的变的