Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, India.
Discipline of Chemical Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat, India.
Ultrasound Med Biol. 2023 Feb;49(2):497-511. doi: 10.1016/j.ultrasmedbio.2022.09.019. Epub 2022 Oct 31.
Ultrasound phantoms mimic the acoustic and mechanical properties of native tissues. Polyvinyl alcohol (PVA) phantoms are used extensively as models for validating ultrasound elastography approaches. However, the viscous properties of PVA phantoms have not been investigated adequately. Glycerol is a viscous liquid that has been reported to increase the speed of sound of phantoms. This study aims to assess the acoustic and viscoelastic properties of PVA phantoms and PVA mixed with glycerol at varying concentrations. The phantoms were fabricated with 10% w/v PVA in water with varying concentrations of glycerol (10%, 15% and 20% v/v) and 2% w/v silicon carbide particles as acoustic scatterers. The phantoms were subjected to either one, two, or three 24-h freeze-thaw cycles. The longitudinal sound speeds of all PVA phantoms were measured, and ranged from 1529 to 1660 m/s. Attenuation spectroscopy was performed in the range of 5 to 20 MHz. The measured attenuation followed a power-law relationship with frequency, wherein the power-law fit constants and exponents ranged from 0.02 to 0.1 dB/cm/MHz and from 1.6 to 1.9, respectively. These results were in agreement with previous reports for soft tissues. Viscoelasticity of PVA phantoms was assessed using rheometry. The estimated values of shear modulus and viscosity using the Kelvin-Voigt and Kelvin-Voigt fractional derivative models were within the range of previously-reported tissue-mimicking phantoms and soft tissues. The number of freeze-thaw cycles were shown to alter the viscosity of PVA phantoms, even in the absence of glycerol. Scanning electron microscopy images of PVA phantoms without glycerol showed a porous hydrogel network, in contrast to those of PVA-glycerol phantoms with non-porous structure. Phantoms fabricated in this study possess tunable acoustic and viscoelastic properties within the range reported for healthy and diseased soft tissues. This study demonstrates that PVA phantoms can be manufactured with glycerol for applications in ultrasound elastography.
超声仿体模拟原生组织的声学和力学特性。聚乙烯醇（PVA）仿体被广泛用作验证超声弹性成像方法的模型。然而，PVA 仿体的粘性特性尚未得到充分研究。甘油是一种粘性液体，据报道可提高仿体的声速。本研究旨在评估 PVA 仿体以及含有不同浓度甘油（10%、15%和 20%v/v）的 PVA 混合物的声学和粘弹性特性。仿体由 10%w/v 的 PVA 溶于水中制成，含有不同浓度的甘油（10%、15%和 20%v/v）和 2%w/v 的碳化硅颗粒作为声散射体。仿体经过一次、两次或三次 24 小时冻融循环。所有 PVA 仿体的纵向声速均进行了测量，范围为 1529 至 1660 m/s。在 5 至 20 MHz 的范围内进行了衰减光谱测量。测量的衰减与频率呈幂律关系，其中幂律拟合常数和指数分别在 0.02 至 0.1 dB/cm/MHz 和 1.6 至 1.9 范围内。这些结果与先前报道的软组织结果一致。使用流变仪评估 PVA 仿体的粘弹性。使用 Kelvin-Voigt 和 Kelvin-Voigt 分数导数模型估算的剪切模量和粘度值在先前报道的组织模拟仿体和软组织的范围内。即使在没有甘油的情况下，冻融循环的次数也会改变 PVA 仿体的粘度。没有甘油的 PVA 仿体的扫描电子显微镜图像显示出多孔水凝胶网络，而含有甘油的 PVA 仿体则显示出非多孔结构。本研究中制造的仿体具有在健康和患病软组织报告的范围内可调节的声学和粘弹性特性。这项研究表明，PVA 仿体可以用甘油制造，用于超声弹性成像应用。
