Apparatus and methods for determining optical tissue properties

An imaging apparatus for determining optical properties of a animal, comprising:

• one or more light sources that are positionable at a plurality of different illumination positions relative to a first surface of the animal;
• a detector positioned to detect light emission measurements from a second surface of the animal that is opposite to the first surface;
• and
• a processor, wherein the processor is configured to:
• measure a surface topography of the second surface of the animal, wherein the second surface has a complex three-dimensional profile;
• conduct tomographic imaging on the animal separately from said measuring a surface topography, the tomographic imaging comprising:
• illuminating the first surface of the animal with light from only a single one of the one or more light sources having a first wavelength and a known illumination power, sequentially at a plurality of specific illumination positions on the first surface;
• and
• for each specific illumination position of the single light source, obtaining light emission measurements from the second surface for a plurality of surface positions of the second surface;
• determine a measured photon density distribution just inside the second surface of the animal from the light emission measurements and the surface topography using a model for photon propagation at a tissue-air interface;
• and
• for each specific illumination position of the single light source, determine a reduced scattering coefficient μs′ and an absorption coefficient μA for the animal based on the specific illumination position of the single light source, the first wavelength of the single light source, the known illumination power of the single light source, the measured surface topography of the second surface, and the light emission measurements for each specific illumination position, wherein the optical properties for the plurality of specific illumination positions of the single light source are individually determined for each specific illumination position of the single light source,
• wherein determining the reduced scattering coefficient μs′ and the absorption coefficient μA comprises:
• using a forward model of photon propagation within the animal that generates, at each iteration, an updated calculated photon density distribution just inside the second surface of the animal;
• during each iteration of the forward model, updating values for μs′ and μA to generate the updated calculated photon density distribution such that the updated values for μs′ and μA yield a best fit between the updated calculated photon density distribution and the measured photon density distribution;
• and
• performing successive iterations of the forward model until the updated calculated photon density distribution is within a predetermined specification of the measured photon density distribution just inside the second surface of the animal.

A non-transitory and tangible computer readable storage medium having computer program instructions stored thereon that, when read by a processor, causes the processor to:

• measure a surface topography of a second surface of an animal, wherein the second surface has a complex three-dimensional profile;
• conduct tomographic imaging on the animal separately from said measuring a surface topography, the tomographic imaging comprising:
• illuminating a first surface of the animal opposite to the second surface with light from a single light source having a first wavelength and a known illumination power, sequentially at a plurality of specific illumination positions on the first surface;
• and
• for each specific illumination position of the single light source, obtaining light emission measurements from the second surface for a plurality of surface positions of the second surface;
• determine a measured photon density distribution just inside the second surface of the animal from the light emission measurements and the surface topography using a model for photon propagation at a tissue-air interface;
• and
• for each specific illumination position of the single light source, determine a reduced scattering coefficient μs′ and an absorption coefficient μA for the animal based on the specific illumination position of the single light source, the first wavelength of the single light source, the known illumination power of the single light source, the measured surface topography of the second surface, and the light emission measurements for each specific illumination position, wherein the optical properties for the plurality of specific illumination positions of the single light source are individually determined for each specific illumination position of the single light source,
• wherein determining the reduced scattering coefficient μs′ and the absorption coefficient μA comprises:
• using a forward model of photon propagation within the animal that generates, at each iteration, an updated calculated photon density distribution just inside the second surface of the animal;
• during each iteration of the forward model, updating values for μs′ and μA to generate the updated calculated photon density distribution such that the updated values for μs′ and μA yield a best fit between the updated calculated photon density distribution and the measured photon density distribution;
• and
• performing successive iterations of the forward model until the updated calculated photon density distribution is within a predetermined specification of the measured photon density distribution just inside the second surface of the animal.