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Quantitative 3D magnetic resonance elastography: Comparison with dynamic mechanical analysis

View Article: PubMed Central - PubMed

ABSTRACT

Purpose: Magnetic resonance elastography (MRE) is a rapidly growing noninvasive imaging technique for measuring tissue mechanical properties in vivo. Previous studies have compared two‐dimensional MRE measurements with material properties from dynamic mechanical analysis (DMA) devices that were limited in frequency range. Advanced DMA technology now allows broad frequency range testing, and three‐dimensional (3D) MRE is increasingly common. The purpose of this study was to compare 3D MRE stiffness measurements with those of DMA over a wide range of frequencies and shear stiffnesses.

Methods: 3D MRE and DMA were performed on eight different polyvinyl chloride samples over 20–205 Hz with stiffness between 3 and 23 kPa. Driving frequencies were chosen to create 1.1, 2.2, 3.3, 4.4, 5.5, and 6.6 effective wavelengths across the diameter of the cylindrical phantoms. Wave images were analyzed using direct inversion and local frequency estimation algorithm with the curl operator and compared with DMA measurements at each corresponding frequency. Samples with sufficient spatial resolution and with an octahedral shear strain signal‐to‐noise ratio > 3 were compared.

Results: Consistency between the two techniques was measured with the intraclass correlation coefficient (ICC) and was excellent with an overall ICC of 0.99.

Conclusions: 3D MRE and DMA showed excellent consistency over a wide range of frequencies and stiffnesses. Magn Reson Med 77:1184–1192, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.

No MeSH data available.


Left: Schematic of the DMA instrument. Right: Photograph of the DMA instrument with the small cylindrical PVC sample in a plastic tube.
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mrm26207-fig-0001: Left: Schematic of the DMA instrument. Right: Photograph of the DMA instrument with the small cylindrical PVC sample in a plastic tube.

Mentions: For each of the eight mixtures, a new approach for DMA was performed on the two small cylindrical tube samples. The measurements were performed using a commercially available instrument (RheoSpectris C500+; Rheolution, Montreal, Quebec, Canada), which introduces shear motion into the small cylindrical tube that contains the sample and uses nondestructive high sensitivity displacement laser measurements at the surface to measure the resulting vibration of the sample. This instrument uses the physical principle of resonant dynamic response of a material confined in a cylindrical tube. As described in more detail previously 15, 16, the resonance eigenmodes of the sample are related to its viscoelasticity. A combination of sequential vibration pulses of different central frequencies and spectral distributions are used to mechanically excite the sample in a wide frequency band. From the corresponding spectrum, a proprietary algorithm is employed to allow accurate shear storage and loss modulus measurements over a broad range of frequencies from 1 to 2000 Hz. This form of DMA, which is sometimes called high‐frequency viscoelasatic spectroscopy, was performed for each mixture at frequencies of 10–250 Hz at 10‐Hz increments approximately 1 h prior to MRE data acquisition. For each mixture at each frequency, five repeated measurements were made on each small cylindrical tube sample for a total of 10 measurements. The average of these 10 measurements was used in subsequent comparisons with MRE. Standard error was computed using the standard deviation and mean for each measurement across all PVC samples. For each mixture at each frequency, the magnitude of the complex shear modulus, storage modulus, and loss modulus in kPa were estimated for comparison with MRE measurements. Figure 1 (Left) shows the schematic of the DMA instrument used in this study, and Figure 1 (Right) shows the photograph of the RheoSpectris C500+ instrument with the PVC sample inside a plastic tube.


Quantitative 3D magnetic resonance elastography: Comparison with dynamic mechanical analysis
Left: Schematic of the DMA instrument. Right: Photograph of the DMA instrument with the small cylindrical PVC sample in a plastic tube.
© Copyright Policy - creativeCommonsBy-nc-nd
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036985&req=5

mrm26207-fig-0001: Left: Schematic of the DMA instrument. Right: Photograph of the DMA instrument with the small cylindrical PVC sample in a plastic tube.
Mentions: For each of the eight mixtures, a new approach for DMA was performed on the two small cylindrical tube samples. The measurements were performed using a commercially available instrument (RheoSpectris C500+; Rheolution, Montreal, Quebec, Canada), which introduces shear motion into the small cylindrical tube that contains the sample and uses nondestructive high sensitivity displacement laser measurements at the surface to measure the resulting vibration of the sample. This instrument uses the physical principle of resonant dynamic response of a material confined in a cylindrical tube. As described in more detail previously 15, 16, the resonance eigenmodes of the sample are related to its viscoelasticity. A combination of sequential vibration pulses of different central frequencies and spectral distributions are used to mechanically excite the sample in a wide frequency band. From the corresponding spectrum, a proprietary algorithm is employed to allow accurate shear storage and loss modulus measurements over a broad range of frequencies from 1 to 2000 Hz. This form of DMA, which is sometimes called high‐frequency viscoelasatic spectroscopy, was performed for each mixture at frequencies of 10–250 Hz at 10‐Hz increments approximately 1 h prior to MRE data acquisition. For each mixture at each frequency, five repeated measurements were made on each small cylindrical tube sample for a total of 10 measurements. The average of these 10 measurements was used in subsequent comparisons with MRE. Standard error was computed using the standard deviation and mean for each measurement across all PVC samples. For each mixture at each frequency, the magnitude of the complex shear modulus, storage modulus, and loss modulus in kPa were estimated for comparison with MRE measurements. Figure 1 (Left) shows the schematic of the DMA instrument used in this study, and Figure 1 (Right) shows the photograph of the RheoSpectris C500+ instrument with the PVC sample inside a plastic tube.

View Article: PubMed Central - PubMed

ABSTRACT

Purpose: Magnetic resonance elastography (MRE) is a rapidly growing noninvasive imaging technique for measuring tissue mechanical properties in vivo. Previous studies have compared two‐dimensional MRE measurements with material properties from dynamic mechanical analysis (DMA) devices that were limited in frequency range. Advanced DMA technology now allows broad frequency range testing, and three‐dimensional (3D) MRE is increasingly common. The purpose of this study was to compare 3D MRE stiffness measurements with those of DMA over a wide range of frequencies and shear stiffnesses.

Methods: 3D MRE and DMA were performed on eight different polyvinyl chloride samples over 20–205 Hz with stiffness between 3 and 23 kPa. Driving frequencies were chosen to create 1.1, 2.2, 3.3, 4.4, 5.5, and 6.6 effective wavelengths across the diameter of the cylindrical phantoms. Wave images were analyzed using direct inversion and local frequency estimation algorithm with the curl operator and compared with DMA measurements at each corresponding frequency. Samples with sufficient spatial resolution and with an octahedral shear strain signal‐to‐noise ratio > 3 were compared.

Results: Consistency between the two techniques was measured with the intraclass correlation coefficient (ICC) and was excellent with an overall ICC of 0.99.

Conclusions: 3D MRE and DMA showed excellent consistency over a wide range of frequencies and stiffnesses. Magn Reson Med 77:1184–1192, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.

No MeSH data available.