Show simple item record

dc.contributor.advisorRogers, Peter H.
dc.contributor.authorGray, Michael D.
dc.date.accessioned2015-06-08T18:19:41Z
dc.date.available2015-06-08T18:19:41Z
dc.date.created2015-05
dc.date.issued2015-03-09
dc.date.submittedMay 2015
dc.identifier.urihttp://hdl.handle.net/1853/53464
dc.description.abstractA new approach to soft tissue elastography is presented. The work was motivated by the need to understand and mitigate the effects of anthropogenic sound on marine mammals. These efforts have been hampered by a lack of knowledge of in vivo tissue viscoelastic moduli. To address this problem, a measurement system concept was developed to non-invasively determine shear viscoelastic properties at tissue depths of over 12 cm – well beyond the capabilities of existing systems. The central design feature of the measurement system is a focused, sectored, annular ultrasonic source that generates a ring-like pressure field. This in turn produces a ring-like radiation force distribution in soft tissue, the response of which is primarily observable as a shear wave field that converges to the center of the force pattern. A second confocal transducer nested inside the shear wave generation source is used to measure the component of the shear wave motion along the beam axis. Propagation speed is estimated from displacement phase changes resulting from drive frequency induced dilation of the forcing radius. Forcing beams are modulated in order to establish shear speed frequency dependence, allowing quantification of shear speed dispersion. This concept for convergent field elastography (CFE) is intended to significantly improve the overall ability to estimate soft tissue shear speeds in thick, complex tissues while keeping within FDA-mandated ultrasound exposure limits. A prototype system was developed and tested in tissue mimicking materials for which properties were independently determined. Experiments were first carried out in a homogeneous material, and subsequently in a material containing elastic contrast inclusions. Transmission experiments with re-hydrated samples of bottlenose dolphin skull and mandibular bone samples were conducted to quantify ultrasonic beam attenuation and distortion effects, and their cumulative impact on CFE shear estimation performance. In addition to supporting marine mammal studies, the techniques developed in this thesis may enable or extend a wide range of human medical diagnostics.
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherGeorgia Institute of Technology
dc.subjectUltrasound
dc.subjectShear
dc.subjectTissue
dc.titleConvergent field elastography
dc.typeText
dc.description.degreePh.D.
dc.contributor.departmentMechanical Engineering
thesis.degree.levelDoctoral
dc.contributor.committeeMemberKu, David N.
dc.contributor.committeeMemberHastings, Mardi
dc.contributor.committeeMemberPrausnitz, Mark
dc.contributor.committeeMemberKetten, Darlene
dc.type.genreDissertation
dc.date.updated2015-06-08T18:19:41Z


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record