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Shear Wave Dispersion as a Potential Biomarker for Cervical Remodeling During Pregnancy: Evidence From a Non-Human Primate Model
Frontiers in Physics ( IF 3.1 ) Pub Date : 2020-12-07 , DOI: 10.3389/fphy.2020.606664
Abel Torres 1 , Mark L Palmeri 2 , Helen Feltovich 3 , Timothy J Hall 4 , Ivan M Rosado-Mendez 1
Affiliation  

Shear wave dispersion (variation of phase velocity with frequency) occurs in tissues with layered and anisotropic microstructure and viscous components, such as the uterine cervix. This phenomenon, mostly overlooked in previous applications of cervical Shear Wave Elasticity Imaging (SWEI) for preterm birth risk assessment, is expected to change drastically during pregnancy due to cervical remodeling. Here we demonstrate the potential of SWEI-based descriptors of dispersion as potential biomarkers for cervical remodeling during pregnancy. First, we performed a simulation-based pre-selection of two SWEI-based dispersion descriptors: the ratio R of group velocities computed with particle-velocity and particle-displacement, and the slope S of the phase velocity vs. frequency. The pre-selection consisted of comparing the contrast-to-noise ratio (CNR) of dispersion descriptors in materials with different degrees of dispersion with respect to a low-dispersive medium. Shear waves induced in these media by SWEI were simulated with a finite-element model of Zener viscoelastic solids. The pre-selection also considered two denoising strategies to improve CNR: a low-pass filter with automatic frequency cutoff determination, and singular value decomposition of shear wave displacements. After pre-selection, the descriptor-denoising combination that produced the largest CNR was applied to SWEI cervix data from 18 pregnant Rhesus macaques acquired at weeks 10 (mid-pregnancy stage) and 23 (late pregnancy stage) of the 24.5-weeks full pregnancy. A maximum likelihood linear mixed-effects model (LME) was used to evaluate the dependence of the dispersion descriptor on pregnancy stage, maternal age, parity and other experimental factors. The pre-selection study showed that descriptor S combined with singular value decomposition produced a CNR 11.6 times larger than the other descriptor and denoising strategy combinations. In the Non-Human Primates (NHP) study, the LME model showed that descriptor S significantly decreased from mid to late pregnancy (−0.37 ± 0.07 m/s-kHz per week, p< 0.00001) with respect to the base value of 15.5 ± 1.9 m/s-kHz. This change was more significant than changes in other SWEI features such as the group velocity previously reported. Also, S varied significantly between the anterior and posterior portions of the cervix (p= 0.02) and with maternal age (p= 0.008). Given the potential of shear wave dispersion to track cervical remodeling, we will extend its application to ongoing longitudinal human studies.



中文翻译:

剪切波色散作为怀孕期间宫颈重塑的潜在生物标志物:来自非人类灵长类动物模型的证据

剪切波色散(相速度随频率的变化)发生在具有层状和各向异性微观结构以及粘性成分的组织中,例如宫颈。这种现象在以前应用宫颈剪切波弹性成像(SWEI)进行早产风险评估时大多被忽视,预计在怀孕期间由于宫颈重塑而发生巨大变化。在这里,我们展示了基于 SWEI 的分散描述符作为妊娠期间宫颈重塑的潜在生物标志物的潜力。首先,我们对两个基于 SWEI 的色散描述符进行了基于模拟的预选:比率使用粒子速度和粒子位移计算的群速度以及斜率S相速度与频率的关系。预选包括比较具有不同色散程度的材料与低色散介质的色散描述符的对比度噪声比 (CNR)。使用齐纳粘弹性固体的有限元模型模拟了 SWEI 在这些介质中引起的剪切波。预选还考虑了两种降噪策略来提高 CNR:具有自动频率截止确定功能的低通滤波器和剪切波位移的奇异值分解。预选后,将产生最大 CNR 的描述子去噪组合应用于 18 只怀孕恒河猴的 SWEI 子宫颈数据,这些数据是在 24.5 周满孕期的第 10 周(妊娠中期)和第 23 周(妊娠晚期)获得的。 。使用最大似然线性混合效应模型(LME)来评估离散描述符对妊娠阶段、母亲年龄、胎次和其他实验因素的依赖性。预选研究表明描述符S与奇异值分解相结合产生的 CNR 比其他描述符和去噪策略组合大 11.6 倍。在非人类灵长类动物(NHP)研究中,LME模型显示描述符S从妊娠中期到晚期显着下降(-0.37±每周 0.07 m/s-kHz,p<0.00001) 相对于基值 15.5±1.9 m/s-kHz。这一变化比其他 SWEI 功能(例如先前报告的群速度)的变化更为显着。此外,子宫颈前部和后部之间的 S 也存在显着差异(p=0.02)和母亲年龄(p=0.008)。鉴于剪切波色散追踪宫颈重塑的潜力,我们将其应用扩展到正在进行的纵向人体研究。

更新日期:2021-02-15
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