Resumen

LOYD, Andre Matthew; AMADOR, Carolina  y  AN, Kai-Nan. THE EFFECTS OF TIME AND MOISTURE ON ELASTICITY IMAGING PHANTOM PHYSICAL AND MECHANICAL PROPERTIES: A PILOT STUDYEFECTOS DE TIEMPO Y HUMEDAD EN LAS PROPIEDADES MECÁNICAS Y FÍSICAS DE UN FANTOMA DE IMÁGENES DE ELASTICIDAD: ESTUDIO PILOTO. Rev. ing. biomed. [online]. 2014, vol.8, n.15, pp.27-35. ISSN 1909-9762.

Elasticity imaging phantoms are used to mimic human tissue as a means of testing and validating non-invasive techniques for measuring mechanical properties of human tissues. Limited studies of phantom stability have shown that phantom stiffness change over time when exposed to air. The goals of this study were to investigate how the physical and mechanical properties of elasticity imaging phantoms change with time and moisture state. Two moisture states were tested; a dry state where the phantom was exposed to open air and a wet state where the phantom was submerged in water for 480 minutes. Polyvinyl alcohol (PVA) phantoms (cylindrical shape) were used. The properties of the phantom were found using flat indentation tests and a test battery that included a precondition test, a 0.05 mm/s triangle test, a 5 mm/s triangle test and a ten-second ramp-and-hold relaxation test. This battery was done at multiple time points: 0, 15, 30, 45, 60, 120, 180, 240, 360 and 480 minutes. At each time point, the modulus, stiffness and relaxation at 10 seconds were calculated. In addition, the mass and volume of the phantoms were measured at each time point. The physical and mechanical properties of the phantoms were found to be statistically dependent on moisture state and time (p<0.05). The stiffness and moduli of the dry samples increased with time while the mass and volume decreased with time. Additionally, a strong correlation was found between the change in mass and change in modulus/stiffness for the dry phantoms. For the wet samples, the modulus and stiffness decreased with time while the mass and volume increase with time. The properties of the phantom begin to change within 15 minutes, the percentage change of the mechanical and physical properties remained, on average, under 10% during the first hour and increased up to 50% during 8 hours. These property changes of phantoms should be considered when using phantoms to test or validate non-invasive techniques.

Palabras clave : Fantomas; Imágenes de elasticidad; Elasticidad; Ensayo mecánico.

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