Vision-based 3D surface motion capture for the DIET breast cancer screening system
International Journal of Computer Applications in Technology
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Elasticity is an important physical property of material.In the clinical practice, elasticity is used for physical examinationin several ways, such as palpation or percussion.Differences in elasticity can help facilitate the diagnosisof tumors and their extent. Elasticity is an essentialproperty in the diagnosis of liver cirrhosis, or soft degenerationin tissue necrosis. In addition, information of tissueelasticity is utilized in virtual reality systems such astelepalpation and computer assisted surgery. It was difficultto obtain such properties in vivo by using conventional measurementmethods. To overcome this problem, magnetic resonanceelastography (MRE) has been developed that providesnoninvasive in vivo measurements of elasticity for humantissue. We summarize this MRE method in this paper.When an object is oscillated from the surface in a knownfrequency, acoustic strain waves propagate into the materialand one can calculate the physical constants of a materialelasticity by the wave velocity. In MRE measurements,a cyclic micromotion caused by the acoustic strain wavesis obtained as an MR image that is synchronized to the oscillation.By measuring the local wavelength of the strainwaves, we can obtain the elasticity constants. Several examplesof MRE image including in vivo measurements areprovided as well as several methods to estimate the localwavelength from MRE images are described in this paper.