Soulioti Danai E, Jones Rebecca M, Pinton Gianmarco F
Lampe Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC 27599, United States of America.
Phys Med Biol. 2025 Aug 11;70(16):165010. doi: 10.1088/1361-6560/adf2f3.
The skull significantly aberrates ultrasound imaging pulses due to its acoustic properties and morphology. However, in addition to aberration of sound waves, the large speed of sound and density mismatch between soft tissue and bone is responsible for multiple reverberations between tissue interfaces and the transducer. Even though a significant amount of research has been dedicated to measuring, characterizing, and correcting the phase aberration caused by the skull, comparatively few results exist on multiple reverberation. The objective of this paper is to quantify reverberation clutter in the brain and to compare degradation from clutter and aberration.A full-wave equation simulating nonlinear propagation in a heterogeneous medium is solved numerically to explore the degrading effects of the human skull. Simulations were performed using isovelocity and clutter subtraction simulations to compare the relative contributions of reverberation and aberration on point spread function degradation.From the performed simulations, it is shown that (a) reverberation is significant in transcranial imaging due to the inclusion of both transmit and receive pulses during imaging, (b) the effect of aberration on image degradation is independent of target brightness whereas the effect of reverberation is dependent on target brightness, (c) reverberation is depth dependent, and (d) the microstructure has little impact on overall reverberation properties in thin skull regions.From this study, it shown that to further improve transcranial ultrasound imaging, especially with respect to lower amplitude and shallower targets, both aberration and reverberation should be addressed.
由于颅骨的声学特性和形态，其会显著使超声成像脉冲产生畸变。然而，除了声波畸变外，软组织与骨骼之间较大的声速和密度失配会导致组织界面与换能器之间产生多次混响。尽管已有大量研究致力于测量、表征和校正由颅骨引起的相位畸变，但关于多次混响的研究结果相对较少。本文的目的是量化大脑中的混响杂波，并比较杂波和畸变造成的图像质量下降。通过数值求解一个模拟非均匀介质中非线性传播的全波方程，来探究人类颅骨的降解效应。使用等速模拟和杂波减法模拟进行仿真，以比较混响和畸变对点扩散函数降解的相对贡献。从所进行的仿真结果可知：（a）由于成像过程中包含发射和接收脉冲，混响在经颅成像中很显著；（b）畸变对图像降解的影响与目标亮度无关，而混响的影响则取决于目标亮度；（c）混响与深度有关；（d）在薄颅骨区域，微观结构对整体混响特性影响不大。从这项研究可知，为了进一步改善经颅超声成像，特别是对于低幅度和较浅目标的成像，应同时解决畸变和混响问题。
