title: Nonlinear elastic behavior of phantom materials for elastography.
abstract: The development of phantom materials for elasticity imaging is reported in this paper. These materials were specifically designed to provide nonlinear stress/strain relationship that can be controlled independently of the small strain shear modulus of the material. The materials are mixtures of agar and gelatin gels. Oil droplet dispersions in these materials provide further control of the small strain shear modulus and the nonlinear parameter of the material. Since these materials are mostly water, they are assumed to be incompressible under typical experimental conditions in elasticity imaging. The Veronda-Westman model for strain energy density provided a good fit to all materials used in this study. Materials with a constant gelatin concentration (3.0% dry weight) but varying agar concentration (0.6-2.8% dry weight) demonstrated the same power law relationship between elastic modulus and agar concentration found for pure agar (1.89 +/- 0.02), consistent with percolation theory, and provided a consistent nonlinearity parameter of 4.5 +/- 0.3. The insights provided by this study will form the basis for stable elastography phantoms with stiffness and nonlinear stress/strain relationships in the background that differ from those in the target.
authors.affiliation: Medical Physics Department, University of Wisconsin, Room 1005, Wisconsin Institutes for Medical Research, 1111 Highland Avenue, Madison, WI 53705, USA.
authors.forename: Theo Z
authors.initials: TZ
authors.lastname: Pavan
authors.forename: Ernest L
authors.initials: EL
authors.lastname: Madsen
authors.forename: Gary R
authors.initials: GR
authors.lastname: Frank
authors.forename: Antonio
authors.initials: A
authors.lastname: Adilton O Carneiro
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Hall
mesh_terms: D055119:Elastic Modulus; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000295:instrumentation*; D017711:Nonlinear Dynamics; D019047:Phantoms, Imaging; D013314:Stress, Mechanical; D013997:Time Factors
references.citation: J Biomech. 1970 Jan;3(1):111-24
references.pmid: 5521524
references.citation: Biosci Biotechnol Biochem. 2000 Aug;64(8):1618-22
references.pmid: 10993147
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2004 Apr;51(4):410-9
references.pmid: 15139542
references.citation: Comput Methods Appl Mech Eng. 2011 Mar 1;200(13-16):1406-1420
references.pmid: 21603066
references.citation: Phys Med Biol. 2007 Jul 7;52(13):3773-90
references.pmid: 17664576
references.citation: Ultrason Imaging. 1998 Oct;20(4):260-74
references.pmid: 10197347
references.citation: Radiographics. 2003 Nov-Dec;23(6):1657-71
references.pmid: 14615571
references.citation: Phys Med Biol. 2005 Dec 7;50(23):5597-618
references.pmid: 16306655
references.citation: Proc Inst Mech Eng H. 1999;213(3):203-33
references.pmid: 10420776
references.citation: Ultrasound Med Biol. 2006 Feb;32(2):261-70
references.pmid: 16464671
references.citation: Ultrason Imaging. 2003 Jan;25(1):17-38
references.pmid: 12747425
references.citation: Phys Med Biol. 2009 Apr 21;54(8):2557-69
references.pmid: 19349660
references.citation: IEEE Trans Ultrason Ferroelectr Freq Control. 2004 May;51(5):532-9
references.pmid: 15217231
references.citation: Phys Med Biol. 2009 Mar 7;54(5):1191-207
references.pmid: 19182325
references.citation: J Acoust Soc Am. 2007 Dec;122(6):3211-9
references.pmid: 18247733
references.citation: Nature. 2005 May 12;435(7039):191-4
references.pmid: 15889088