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U.S. Department of Health and Human Services

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Research Project: Optical Spectroscopy for Tissue Diagnostics

One of the primary research areas in the Optical Diagnostic Devices Laboratory is optical spectroscopy.  This technique forms the basis of numerous minimally- or non-invasive clinical devices with a range of applications from tissue oximetry to bilirubinometry to early detection of a variety of cancers including those arising in mucosal tissues lining the lungs, cervix and gastrointestinal tract. Our efforts are geared towards achieving a quantitative understanding basic light-tissue interactions and developing computational tools to elucidate the basic mechanisms of novel spectroscopic and imaging devices.

 

Determination of Mucosal Tissue Optical Properties

We have developed a novel multi-wavelength optical property measurement system and implemented this system to determine absorption and scattering coefficients of porcine mucosal and liver tissues with a fiberoptic probe.   This data is critical for performing realistic theoretical estimates and computational modeling of light propagation in tissue, particularly for optical spectroscopy devices used for precancer detection.  We have subsequently modified this system to perform simultaneous measurements of optical properties in two-layer tissues.  Theoretical analyses and layered phantom measurements indicate that optical property estimation accuracy is highly dependent on the thickness and optical properties of individual layers.  Furthermore, inherent variations in tissue optical properties and morphology remain significant challenges.

 

Computational Modeling of Optical Spectroscopy

In prior studies we have developed computational models to simulate light-tissue interaction at individual wavelengths for fluorescence spectroscopy devices.  More recently, we have developed a novel Monte Carlo-based approach for rapid simulation of fiberoptic-based reflectance spectroscopy devices.  This technique was validated and implemented to study several example cases based on normal and cancerous breast tissues.  The high speed of single-wavelength simulations makes it possible to swiftly generate predicted variations in optical spectra over a wide range of wavelengths as a function of tissue optical properties, morphologies and optical device design (e.g., probe geometry).  This work represents a significant advance towards a practical computational tool for understanding and predicting the performance of novel optical diagnostic devices for a variety of applications including early, minimally-invasive cancer detection.

 
Reflectance spectra of adipose (left) and malignant (right) breast tissues from illumination-detection fibers (r = fiber radius; Rt = total reflectance).