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dc.contributor.authorLiu, Yajingen_US
dc.date.accessioned2014-03-14T20:35:42Z
dc.date.available2014-03-14T20:35:42Z
dc.date.issued2009-05-05en_US
dc.identifier.otheretd-05082009-162855en_US
dc.identifier.urihttp://hdl.handle.net/10919/32395
dc.description.abstractLaser-based photo-thermal therapies can provide minimally-invasive treatment of cancers. Their effectiveness is limited by light penetration depth in tissue due to its highly scattering properties. The highly disordered refractive index distribution in tissue leads to multiple-scattering of incident light. It has been hypothesized that mechanical compression has a great potential to enhance the capabilities of laser therapy by inducing localized water transport, decreasing the refractive index mismatch, and decreasing the scattering coefficient of tissue. To better understand this process, we investigated the refractive index change of ex-vivo dog skin during mechanical compression using a swept-source optical coherence tomography (OCT) device built in our lab. The Lorentz-Lorenz rule of mixtures was applied to evaluate the water and protein weight fraction of tissue simultaneously. Results show that the refractive index of skin increased from 1.38 to 1.52 during compression and water content decreased about 60%-70% when the skin sample was compressed by 70%. In addition, we conducted compression experiments on human finger, palm, back of hand, and front of forearm in vivo. OCT images of these skin sites before and after compression by 1 minute were compared. Optical thickness of epidermis and light penetration depth in the dermis were measured. The extended Huygens-Fresnel model was applied to measure the scattering coefficient μs of skin specimens. μs of skin was measured to be about 10-17 mm-1 before compression and decreased 60%-80% after compression, which increases the averaged light intensity by 2-7 dB and almost doubles light penetration depth in dermis. It is quite significant in laser therapies especially for treating epithelia cancers which originate at 1-2 mm beneath the tissue surface. In the OCT imaging of skin dehydration experiment, we conclude that dehydration is an important mechanism of mechanical clearing.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartETD.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectscattering coefficienten_US
dc.subjectextended Huygens-Fresnel Modelen_US
dc.subjectrefractive indexen_US
dc.subjectoptical propertiesen_US
dc.subjectswept source Optical Coherence Tomography (OCT)en_US
dc.titleMeasurement of tissue optical properties during mechanical compression using swept source optical coherence tomographyen_US
dc.typeThesisen_US
dc.contributor.departmentBiomedical Engineeringen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineBiomedical Engineeringen_US
dc.contributor.committeechairRylander, Christopher G.en_US
dc.contributor.committeememberXu, Yongen_US
dc.contributor.committeememberWang, Geen_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05082009-162855/en_US
dc.date.sdate2009-05-08en_US
dc.date.rdate2009-06-04
dc.date.adate2009-06-04en_US


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