title: Detection of optical and mechanical property inhomogeneities in tissue mimicking phantoms using an ultrasound assisted optical probe.
abstract: We discuss the issue of separating contributions from mechanical and optical properties of a moderately scattering tissue phantom to the modulation depth (M) of intensity autocorrelation measured in an ultrasound-assisted optical tomography system using axial and transverse illuminations. For axial illumination, M is affected by both the displacement and absorption coefficient, more prominently by displacement. But transverse illumination has very little contribution from displacement of scattering centers. Since displacement is related to the elastic property of the insonified region, we show that there is a possibility of separating the contributions from elastic and optical properties of the insonified region using axial and transverse illuminations. The main conclusions of our study using moderately scattering phantoms are: 1. axial illumination is the best for mapping storage modulus inhomogeneities, but M is also affected by optical absorption; 2. transverse illumination is the best for mapping absorption inhomogeneities; and 3. for the practically relevant case of an inclusion with larger storage modulus and absorption, both illuminations produced large contrast in M. When the scattering coefficient is high, the angle dependence of illumination is lost and the present method is shown to fail to separate these contributions based on direction of illumination.
authors.affiliation: Thangal Kunju Musaliar College of Engineering, Department of Electrical and Electronics Engineering, Kollam, 691005, India.
authors.forename: C Usha
authors.initials: CU
authors.lastname: Devi
authors.forename: R Sreekumari Bharat
authors.initials: RS
authors.lastname: Chandran
authors.forename: R Mohan
authors.initials: RM
authors.lastname: Vasu
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Sood
mesh_terms: D016880:Anisotropy; D003238:Connective Tissue / Q000000981:diagnostic imaging* / Q000502:physiology*; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000295:instrumentation* / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D008027:Light; D019047:Phantoms, Imaging; D012542:Scattering, Radiation; D013314:Stress, Mechanical; D041622:Tomography, Optical / Q000295:instrumentation / Q000379:methods*; D014159:Transducers