Name: viscoelastic characterization of soft tissue-mimicking gelatin phantoms using indentation and magnetic resonance elastography
Uploaded: 2022-05-10T15:00:00
Description: Watch this Scientific Journal Video about Viscoelastic Characterization of Soft Tissue-Mimicking Gelatin Phantoms using Indentation and Magnetic Resonance Elastography at JoVE.com

Funding support from the National Natural Science Foundation of China (grant 31870941), Natural Science Foundation of Shanghai (grant 22ZR1429600), and the Science and Technology Commission of Shanghai Municipality (grant 19441907700) is acknowledged.

1. Gelatin phantom preparation
<ol>
	<li>Weigh gelatin, glycerol, and water according to Table 1. Mix the gelatin powder with water to obtain the gelatin solution. 
	NOTE: The concentrations of the individual components for preparing the two phantoms are shown in Table 1. The higher the concentration of gelatin, the stiffer the phantom.</li>
	<li>Heat the gelatin solution to 60 &#176;C in a water bath. Add glycerol to the gelatin solution while maintaining the tem...

<ol>
	<li>Qiu, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viscoelastic+characterization+of+injured+brain+tissue+after+controlled+cortical+impact+(CCI)+using+a+mouse+model.">Viscoelastic characterization of injured brain tissue after controlled cortical impact (CCI) using a mouse model.</a> Journal of Neuroscience Methods. 330, 108463 (2020).</li><li>Garcia, K. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+patterns+of+cortical+expansion+during+folding+of+the+preterm+human+brain.">Dynamic patterns of cortical expansion during folding of the preterm human brain.</a> Proceedings of the National Academy of Sciences of the United States of America. 115 (12), 3156-3161 (2018).</li><li>Qiu, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterizing+viscoelastic+properties+of+breast+cancer+tissue+in+a+mouse+model+using+indentation.">Characterizing viscoelastic properties of breast cancer tissue in a mouse model using indentation.</a> Journal of Biomechanics. 69, 81-89 (2018).</li><li>Yin, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+method+for+quantification+and+3D+visualization+of+brain+tumor+adhesion+using+slip+interface+imaging+in+patients+with+meningiomas.">A new method for quantification and 3D visualization of brain tumor adhesion using slip interface imaging in patients with meningiomas.</a> European Radiology. 31 (8), 5554-5564 (2021).</li><li>Streitberger, K. -. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+tissue+fluidity+influences+brain+tumor+progression.">How tissue fluidity influences brain tumor progression.</a> Proceedings of the National Academy of Sciences of the United States of America. 117 (1), 128 (2020).</li><li>Bunevicius, A., Schregel, K., Sinkus, R., Golby, A., Patz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=REVIEW:+MR+elastography+of+brain+tumors.">REVIEW: MR elastography of brain tumors.</a> NeuroImage: Clinical. 25, 102109 (2020).</li><li>Namani, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elastic+characterization+of+transversely+isotropic+soft+materials+by+dynamic+shear+and+asymmetric+indentation.">Elastic characterization of transversely isotropic soft materials by dynamic shear and asymmetric indentation.</a> Journal of Biomechanical Engineering. 134 (6), 061004 (2012).</li><li>Potter, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+small-specimen+planar+biaxial+testing+system+with+full+in-plane+deformation+control.">A novel small-specimen planar biaxial testing system with full in-plane deformation control.</a> Journal of Biomechanical Engineering. 140 (5), 0510011 (2018).</li><li>Zhang, W., Feng, Y., Lee, C. -. 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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viscoelastic+properties+of+soft+gels:+comparison+of+magnetic+resonance+elastography+and+dynamic+shear+testing+in+the+shear+wave+regime.">Viscoelastic properties of soft gels: comparison of magnetic resonance elastography and dynamic shear testing in the shear wave regime.</a> Physics in Medicine and Biology. 56 (19), 6379-6400 (2011).</li><li>Feng, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+multi-purpose+electromagnetic+actuator+for+magnetic+resonance+elastography.">A multi-purpose electromagnetic actuator for magnetic resonance elastography.</a> Magnetic Resonance Imaging. 51, 29-34 (2018).</li><li>Zeng, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nonlinear+inversion+MR+elastography+with+low-frequency+actuation.">Nonlinear inversion MR elastography with low-frequency actuation.</a> IEEE Transactions on Medical Imaging. 39 (5), 1775-1784 (2020).</li><li>Wang, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+magnetic+resonance+elastography+with+multiphase+radial+encoding+and+harmonic+motion+sparsity+based+reconstruction.">Fast magnetic resonance elastography with multiphase radial encoding and harmonic motion sparsity based reconstruction.</a> Physics in Medicine and Biology. 67 (2), (2022).</li><li>Herraez, M. 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Gelatin phantoms are commonly used as tissue-mimicking materials for testing and validation of algorithms and devices17,19,22,23,24,25,26,27. One of the pioneering studies using the gelatin phantom to compare MRE and dynamic shear testing was presented by O...

Most of the soft biological tissues appear to have viscoelastic properties that are important to understand their injury and development1,2. In addition, viscoelastic properties are important biomarkers in the diagnosis of a variety of diseases such as fibrosis and cancer3,4,5,6. Therefore, the characterization of viscoelastic properties of soft tissues is crucial. Among the many characterization techniques used, ex vivo mechanical testing of tissue samples and in vivo elastography using biomedical imaging are the two widely used methods.
Although various mechanical testing techniques have been used for soft tissue characterization, the requirements for sample size and testing conditions are not easy to be satisfied. For example, shear testing needs to have samples fixed firmly between the shear plates7. Biaxial testing is more suitable for membrane tissue and has specific clamping requirements8,9. A compression test is commonly used for tissue testing, but cannot characterize specific positions within one sample10. The indentation test does not have additional requirements to fix the tissue sample and can be used to measure many biological tissue samples such as the brain and liver. In addition, with a small indenter head, regional properties within a sample could be tested. Therefore, indentation tests have been adopted to test a variety of soft tissues1,3,11.
Characterizing the biomechanical properties of soft tissues in vivo is important for translational studies and clinical applications of biomechanics. Biomedical imaging modalities such as ultrasound (US) and magnetic resonance (MR) imaging are the most used techniques. Although US imaging is relatively cheap and easy to carry out, it suffers from low contrast and is hard to measure organs such as the brain. Capable of imaging deep structures, MR Elastography (MRE) could measure a variety of soft tissues6,12, especially the brain13,14. With applied external vibration, MRE could measure the viscoelastic properties of soft tissues at a specific frequency.
Studies have shown that at 50-60 Hz, the shear modulus of the normal brain is ~1.5-2.5kPa5,6,13,14,15 and ~2-2.5 kPa for normal liver16. Therefore, gelatin phantoms that have similar biomechanical properties have been widely used for mimicking soft tissues for testing and validation17,18,19. In this protocol, gelatin phantoms with two different concentrations were prepared and tested. Viscoelastic properties of the gelatin phantoms were characterized using a custom-built electromagnetic MRE device14 and an indentation device1,3. The testing protocols could be used for testing many soft tissues such as the brain or liver.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>24-channel head &#38; Neck coil</td>
			<td>United Imaging Healthcare</td>
			<td>100120</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>3T MR Scanner</td>
			<td>United Imaging Healthcare</td>
			<td>uMR 790</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Acquisition board</td>
			<td>Advantech Co</td>
			<td>PCI-1706U</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Computer-Windows</td>
			<td>HP</td>
			<td>790-07</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Electromagnetic actuator</td>
			<td>Shanghai Jiao Tong University</td>
			<td></td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Function generator</td>
			<td>RIGOL</td>
			<td>DG1022Z</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Gelatin</td>
			<td>CARTE D&#8217;OR</td>
			<td></td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Vance Bioenergy Sdn.Bhd</td>
			<td></td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Indenter control program</td>
			<td>custom-designed</td>
			<td></td>
			<td>Software; accessed via: https://github.com/aaronfeng369/FengLab_indentation_code.</td>
		</tr>
		<tr>
			<td>Laser sensor</td>
			<td>Panasonic</td>
			<td>HG-C1050</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Load cell</td>
			<td>Transducer Technique</td>
			<td>GSO-10</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>Mathworks</td>
			<td></td>
			<td>Software</td>
		</tr>
		<tr>
			<td>Power amplifier</td>
			<td>Yamaha</td>
			<td>A-S201</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Voice coil electric motor</td>
			<td>SMAC Corporation</td>
			<td>DB2583</td>
			<td>Equipment</td>
		</tr>
	</tbody>
</table>

viscoelastic characterization of soft tissue-mimicking gelatin phantoms using indentation and magnetic resonance elastography

Characterization of biomechanical properties of soft biological tissues is important to understand the tissue mechanics and explore the biomechanics-related mechanisms of disease, injury, and development. The mechanical testing method is the most straightforward way for tissue characterization and is considered as verification for in vivo measurement. Among the many ex vivo mechanical testing techniques, the indentation test provides a reliable way, especially for samples that are small, hard to fix, and viscoelastic such as brain tissue. Magnetic resonance elastography (MRE) is a clinically used method to measure the biomechanical properties of soft tissues. Based on shear wave propagation in soft tissues recorded using MRE, viscoelastic properties of soft tissues can be estimated in vivo based on wave equation. Here, the viscoelastic properties of gelatin phantoms with two different concentrations were measured by MRE and indentation. The protocols of phantom fabrication, testing, and modulus estimation have been presented.

Following the MRE protocol, a clear shear wave propagation in the gelatin phantoms at 40 and 50 Hz were observed (Figure 3). The viscoelastic properties measured from MRE, and indentation tests are shown in Figure 4. The estimated G&#39; and G&#34; values at each testing for each phantom are summarized in Table 2. Following the indentation protocol, the viscoelastic properties of each phantom at each test point are summarized in Table 3<...

Watch this Scientific Journal Video about Viscoelastic Characterization of Soft Tissue-Mimicking Gelatin Phantoms using Indentation and Magnetic Resonance Elastography at JoVE.com

Viscoelastic Characterization of Soft Tissue-Mimicking Gelatin Phantoms using Indentation and Magnetic Resonance Elastography

This article presents a demonstration and summary of protocols of making gelatin phantoms that mimic soft tissues, and the corresponding viscoelastic characterization using indentation and magnetic resonance elastography.

Characterization of biomechanical properties of soft biological tissues is important to understand the tissue mechanics and explore the ...

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