Balbis S, Roatta S, Guiot C
INFM, Torino, Italy.
Ultrasound Med Biol. 2005 Jan;31(1):65-77. doi: 10.1016/j.ultrasmedbio.2004.09.007.
In clinical practice, blood velocity estimations from Doppler examination of curved vascular segments are normally different from those of nearby straight segments. The observed "accelerations," sometimes considered as a sort of stochastic disturbances, can actually be related to very specific physical effects due to vessel curvature (i.e., the development of nonaxial velocity [NAV] components) and the spreading of the axial velocity direction in the Doppler sample volume with respect to the insonation axis. The relevant phenomena and their dependence on the radius of curvature of the vessels and on the insonation angle are investigated with a beam-vessel geometry as close as possible to clinical setting, with the simplifying assumptions of steady flow, mild vessel curvature, uniform ultrasonic beam and complete vessel insonation. The insonation angles that minimize the errors are provided on the basis of the study results.
在临床实践中，通过对弯曲血管段进行多普勒检查来估计血流速度，其结果通常与附近直血管段的血流速度估计值不同。观察到的“加速度”，有时被视为一种随机干扰，实际上可能与血管曲率引起的非常特定的物理效应有关（即非轴向速度[NAV]分量的产生），以及轴向速度方向在多普勒采样容积内相对于声束轴的扩展有关。采用尽可能接近临床实际的束-血管几何模型，在稳定流、血管曲率较小、超声束均匀且血管完全被声束照射等简化假设下，研究了相关现象及其对血管曲率半径和声束入射角的依赖性。根据研究结果给出了使误差最小化的声束入射角。
