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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.


Related in: MedlinePlus

(A) Photograph of the MRE cylindrical phantom. (B) Sectional schematic of the passive driver. The area within the manifold chamber is nonvibrating. The phantom contacts the driver only along the edges indicated by the green arrow and held in position by the adhesive surface in the blue region. (C) Photograph of the custom‐built MRE passive driver. The vibrating area is shaded in blue, and the contact point with the phantom is a circular ring within the vibrating area represented by a pale black circle (indicated by the green arrow).
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mrm26207-fig-0002: (A) Photograph of the MRE cylindrical phantom. (B) Sectional schematic of the passive driver. The area within the manifold chamber is nonvibrating. The phantom contacts the driver only along the edges indicated by the green arrow and held in position by the adhesive surface in the blue region. (C) Photograph of the custom‐built MRE passive driver. The vibrating area is shaded in blue, and the contact point with the phantom is a circular ring within the vibrating area represented by a pale black circle (indicated by the green arrow).

Mentions: Mechanical vibrations were introduced into the cylindrical phantom using a commercially available pneumatic active driver (Resoundant Inc., Rochester, Minnesota, USA) and a custom‐made MRE passive driver. The cylindrical phantoms were placed on top of the passive driver (Fig. 2A), which was designed to cause the phantom to move uniformly in the axial direction of the cylinder. Figure 2B shows the sectional schematic of the custom‐designed passive driver. Sound waves from the active pneumatic driver entered the nonvibrating area in the manifold chamber, which has a hard plastic surface that enters the vibrating area. The passive driver has an adhesive surface that was achieved using a 1.15‐mm‐thick, two‐sided adhesive tape in the vibrating region to eliminate unwanted right‐to‐left and superior–inferior drift during vibration and a circular marking to aid in phantom positioning (Fig. 2C). The driver only contacted the phantom around the bottom edge and not the entire bottom surface, as observed in the schematic in Figure 2B, reducing the amount of longitudinal wave energy introduced into the phantom to minimize phase wraps. This setup resulted in the side walls of the phantom becoming the source of shear wave generation and caused waves to propagate from the phantom edge to the center.


Quantitative 3D magnetic resonance elastography: Comparison with dynamic mechanical analysis
(A) Photograph of the MRE cylindrical phantom. (B) Sectional schematic of the passive driver. The area within the manifold chamber is nonvibrating. The phantom contacts the driver only along the edges indicated by the green arrow and held in position by the adhesive surface in the blue region. (C) Photograph of the custom‐built MRE passive driver. The vibrating area is shaded in blue, and the contact point with the phantom is a circular ring within the vibrating area represented by a pale black circle (indicated by the green arrow).
© Copyright Policy - creativeCommonsBy-nc-nd
Related In: Results  -  Collection

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

mrm26207-fig-0002: (A) Photograph of the MRE cylindrical phantom. (B) Sectional schematic of the passive driver. The area within the manifold chamber is nonvibrating. The phantom contacts the driver only along the edges indicated by the green arrow and held in position by the adhesive surface in the blue region. (C) Photograph of the custom‐built MRE passive driver. The vibrating area is shaded in blue, and the contact point with the phantom is a circular ring within the vibrating area represented by a pale black circle (indicated by the green arrow).
Mentions: Mechanical vibrations were introduced into the cylindrical phantom using a commercially available pneumatic active driver (Resoundant Inc., Rochester, Minnesota, USA) and a custom‐made MRE passive driver. The cylindrical phantoms were placed on top of the passive driver (Fig. 2A), which was designed to cause the phantom to move uniformly in the axial direction of the cylinder. Figure 2B shows the sectional schematic of the custom‐designed passive driver. Sound waves from the active pneumatic driver entered the nonvibrating area in the manifold chamber, which has a hard plastic surface that enters the vibrating area. The passive driver has an adhesive surface that was achieved using a 1.15‐mm‐thick, two‐sided adhesive tape in the vibrating region to eliminate unwanted right‐to‐left and superior–inferior drift during vibration and a circular marking to aid in phantom positioning (Fig. 2C). The driver only contacted the phantom around the bottom edge and not the entire bottom surface, as observed in the schematic in Figure 2B, reducing the amount of longitudinal wave energy introduced into the phantom to minimize phase wraps. This setup resulted in the side walls of the phantom becoming the source of shear wave generation and caused waves to propagate from the phantom edge to the center.

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.


Related in: MedlinePlus