Optical scattering properties in tissue are diagnostic markers, ingredients to increasingly sophisticated models, and undergird many optical imaging modalities. Advances in all these areas hinge on obtaining high fidelity scattering measurements. A new optical scattering goniometry method is discussed which measures scattering into 4π sr from small (~100um) tissue regions in flat-mounted samples.
This novel tissue scattering gonoimeter images the back focal plane of two opposing microscope objectives to collect light in the forward and backward direction and has several key advantages: (1) scanning the incident angle allows measurement of scattering over 4π steradians to determine the complete scattering phase function of tissue, (2) specificity of measuring scattering from small ~50um regions combined with obliquely sectioned tissue allows mapping of layered tissue, (3) spectral characterization through tuning illumination wavelength, (4) concurrent measurement of scattering coefficient. This opens up the prospect of a new level of detail in the characterization of optical scattering from tissue, including distinguishing properties of thin layers.
A tissue system of particular interest and an excellent candidate on which to apply this new goniometry method is the retina. Existing measurements are limited to bulk retina properties or inferred from methodologies that do not have access to transmitted scattering. Scattering coefficient and anisotropy measurements are presented for the various retinal layers. These novel measurements may be used to model light transport and scattering in the retina. Examples of modeling imaging modalities based on scattered light are discussed.
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