Ms. Gloria M. Spirou Profile

Gloria M. Spirou

SPIE Involvement:

Author

Proceedings Article | 8 March 2006 Paper

Examination of contrast mechanisms in optoacoustic imaging of thermal lesions

Christian Richter, Gloria Spirou, Alexander Oraevsky, William Whelan, Michael Kolios

Proceedings Volume 6086, 60861K (2006) https://doi.org/10.1117/12.650692

KEYWORDS: Absorption, Liver, Tissue optics, Tissues, Scattering, Optical properties, Signal detection, Acoustics, Transducers, Laser tissue interaction

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Optoacoustic Imaging is based on the thermal expansion of tissue caused by a temperature rise due to absorption of short laser pulses. At constant laser fluence, optoacoustic image contrast is proportional to differences in optical absorption and the thermoacoustic efficiency, expressed by the Grueuneisen parameter, Γ. Γ is proportional to the thermal expansion coefficient, the sound velocity squared and the inverse heat capacity at constant pressure. In thermal therapies, these parameters may be modified in the treated area. In this work experiments were performed to examine the influence of these parameters on image contrast. A Laser Optoacoustic Imaging System (LOIS, Fairway Medical Technologies, Houston, Texas) was used to image tissue phantoms comprised of cylindrical Polyvinyl Chloride Plastisol (PVCP) optical absorbing targets imbedded in either gelatin or PVCP as the background medium. Varying concentrations of Black Plastic Color (BPC) and titanium dioxide (TiO₂) were added to targets and background to yield desired tissue relevant optical absorption and effective scattering coefficients, respectively. In thermal therapy experiments, ex-vivo bovine liver was heated with laser fibres (805nm laser at 5 W for 600s) to create regions of tissue coagulation. Lesions formed in the liver tissue were visible using the LOIS system with reasonable correspondence to the actual region of tissue coagulation. In the phantom experiments, contrast could be seen with low optical absorbing targets (μ_a of 0.50cm^-1 down to 0.13cm-1) embedded in a gelatin background (see manuscript for formula). Therefore, the data suggest that small objects (< 5mm) with low absorption coefficients (in the range < 1cm^-1) can be imaged using LOIS. PVCP-targets in gelatin were visible, even with the same optical properties as the gelatin, but different Γ. The enhanced contrast may also be caused by differences in the mechanical properties between the target and the surrounding medium. PVCP-targets imbedded in PVCP produced poorer image contrast than PVCP-targets in gelatin with comparable optical properties. The preliminary investigation in tissue equivalent phantoms indicates that in addition to tissue optical properties, differences in mechanical properties between heated and unheated tissues may be responsible for image contrast. Furthermore, thermal lesions in liver tissue, ex-vivo, can be visualized using an optoacoustic system.

Proceedings Article | 12 July 2004 Paper

Development and testing of an optoacoustic imaging system for monitoring and guiding prostate cancer therapies

Gloria Spirou, I. Alex Vitkin, B. Wilson, William Whelan, Paul Henrichs, Ketan Mehta, Tom Miller, Andrew Yee, James Meador, Alexander Oraevsky

Proceedings Volume 5320, (2004) https://doi.org/10.1117/12.535360

KEYWORDS: Tissue optics, Absorption, Transducers, Tissues, Optical properties, Prostate, Therapeutics, Photodynamic therapy, Acoustics, Imaging systems

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Proceedings Article | 12 July 2004 Paper

Three-dimensional photothermoacoustic depth-profilometric imaging by use of a linear frequency sweep lock-in heterodyne method

Ying Fan, Andreas Mandelis, Gloria Spirou, I. Alex Vitkin, William Whelan

Proceedings Volume 5320, (2004) https://doi.org/10.1117/12.537856

KEYWORDS: Acoustics, Solids, Absorption, Biomedical optics, Tissue optics, Transducers, Modulation, Imaging systems, Scattering, Interfaces

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Conference Committee Involvement (3)

Photons Plus Ultrasound: Imaging and Sensing 2008: The Ninth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

20 January 2008 | San Jose, California, United States

Photons Plus Ultrasound: Imaging and Sensing 2007: The Eighth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

20 January 2007 | San Jose, California, United States

Photons Plus Ultrasound Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

22 January 2006 | San Jose, California, United States

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