Li W, Lancée C T, Céspedes E I, van der Steen A F, Bom N
Thoraxcentre, Erasmus University Rotterdam, The Netherlands.
J Acoust Soc Am. 1997 Dec;102(6):3785-94. doi: 10.1121/1.420141.
When blood particles travel through an intravascular ultrasound imaging plane, the received echo signals decorrelate at a rate that is related to the flow velocity. In this paper, the feasibility of extracting blood velocity from the decorrelation function of radio frequency signals was investigated through theoretical analysis and computer simulation. A computer model based on the impulse response method was developed to generate the ultrasound field of a 30-MHz intravascular transducer. The decorrelation due to the scatterer displacement as well as other nonmotion related decorrelation sources were studied. The computer simulations show that the decorrelation function is linearly related to the lateral displacement. The monotonic relationship between correlation and displacement provides possibilities to estimate flow velocity with decorrelation measurements. Because of the complexity of the beam profile in the near field, assessment of local velocities requires detailed knowledge of the decorrelation at each axial beam position. Sources of signal decorrelation other than the lateral displacement may cause a bias in the decorrelation based velocity measurements. For localized decorrelation estimation, measurement variations in small range windows present a major challenge. An approach based on multiple decorrelation measurements should be adopted in order to reduce the variations. In conclusion, results of this study suggest that it is feasible to measure flow velocity by quantifying the decorrelation of intravascular ultrasound signals from blood.
当血液颗粒穿过血管内超声成像平面时，接收到的回波信号会以与流速相关的速率去相关。本文通过理论分析和计算机模拟研究了从射频信号的去相关函数中提取血流速度的可行性。开发了一种基于脉冲响应方法的计算机模型，以生成30MHz血管内换能器的超声场。研究了由散射体位移引起的去相关以及其他与非运动相关的去相关源。计算机模拟表明，去相关函数与横向位移呈线性相关。相关性与位移之间的单调关系为通过去相关测量估计流速提供了可能性。由于近场中波束轮廓的复杂性，评估局部速度需要详细了解每个轴向波束位置处的去相关情况。除横向位移之外的信号去相关源可能会导致基于去相关的速度测量产生偏差。对于局部去相关估计，小范围窗口内的测量变化是一个主要挑战。为了减少变化，应采用基于多次去相关测量的方法。总之，本研究结果表明，通过量化血管内超声信号与血液之间的去相关来测量流速是可行的。
