Applied Sciences, Delft University of Technology, Lorentzweg 1, Delft, 2628 CJ, The Netherlands.
Biomedical Engineering, Department of Cardiology, Erasmus MC, University Medical Center Rotterdam, Doctor Molewaterplein 40, Rotterdam, 3015 GD, The Netherlands.
J Acoust Soc Am. 2021 Jul;150(1):428. doi: 10.1121/10.0005646.
Shear wave elastography (SWE) has the potential to determine cardiac tissue stiffness from non-invasive shear wave speed measurements, important, e.g., for predicting heart failure. Previous studies showed that waves traveling in the interventricular septum (IVS) may display Lamb-like dispersive behaviour, introducing a thickness-frequency dependency in the wave speed. However, the IVS tapers across its length, which complicates wave speed estimation by introducing an additional variable to account for. The goal of this work is to assess the impact of tapering thickness on SWE. The investigation is performed by combining in vitro experiments with acoustic radiation force (ARF) and 2D finite element simulations, to isolate the effect of the tapering curve on ARF-induced and natural waves in the heart. The experiments show a 11% deceleration during propagation from the thick to the thin end of an IVS-mimicking tapered phantom plate. The numerical analysis shows that neglecting the thickness variation in the wavenumber-frequency domain can introduce errors of more than 30% in the estimation of the shear modulus, and that the exact tapering curve, rather than the overall thickness reduction, determines the dispersive behaviour of the wave. These results suggest that septal geometry should be accounted for when deriving cardiac stiffness with SWE.
剪切波弹性成像（SWE）具有通过非侵入性剪切波速度测量来确定心肌组织硬度的潜力，这对于预测心力衰竭非常重要。先前的研究表明，在室间隔（IVS）中传播的波可能表现出类似 Lamb 的频散行为，从而在波速中引入厚度-频率依赖性。然而，IVS 在其长度上逐渐变细，这通过引入一个额外的变量来解释，从而使波速估计变得复杂。这项工作的目的是评估变细厚度对 SWE 的影响。该研究通过结合体外实验和声辐射力（ARF）和 2D 有限元模拟，来隔离变细曲线对心脏中 ARF 诱导和自然波的影响。实验表明，在从厚端到薄端传播过程中，IVS 模拟变细的幻影板的速度降低了 11%。数值分析表明，在波数-频率域中忽略厚度变化会导致剪切模量估计中的误差超过 30%，并且准确的变细曲线而不是整体厚度减小决定了波的频散行为。这些结果表明，在用 SWE 推导心脏硬度时，应该考虑室间隔的几何形状。
