The invention features a calibration method for diffuse optical measurements that corrects transmittance measurements between a source and a detector for factors unrelated to sample properties. The calibration method is based on the same set of transmittance measurements that are subsequently corrected by the calibration and used in imaging and/or spectroscopy applications. The calibration method involves a forward calculation for each of multiple source-detector pairs based on an approximate model of the sample, and a minimization of an expression that depends on the forward calculations and the transmittance measurements to determine self-consistent coupling coefficients for every source-detector pair. Once the coupling coefficients have been determined, they can be used to correct the transmittance measurements. If desired, an inverse calculation can be performed on the corrected sample measurements to determine spatial variations in the optical properties of the sample. If necessary, the calibration can be repeated and iteratively improved, whereby the optical properties determined by the inverse calculation in an earlier iteration are used to improve the sample model for the forward calculation in a subsequent iteration.
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application No. 60/154,423, filed on Sep. 17, 2000, which is incorporated herein by reference in its entirety.
A method and system for minimizing inter-coefficient crosstalk in imaging the internal properties of a scattering medium. The method and system minimizing inter-coefficient. crosstalk in image reconstruction by solving a system of linear perturbation equations with the use of relative detector values, weight matrix scaling, and constraints based on either the know or unknown direction of the perturbations in the medium's properties. The constraint being either (1) positive or negative corresponding to the direction of a known perturbations, or (2) solving the system of equations with both positive and negative constraints and summing the results where the direction of the perturbations are unknown. The advantages of the inventive method and system result in effective isolation of absorption and scattering coefficient variations, even for complex combinations of perturbations in these coefficients.
A method for modeling optical scattering includes an initial step of defining a zero-th order structure (an idealized representation) for a subject including a perturbation domain and a background material. A Green's function and a zero-th order wave function are obtained for the zero-th order structure using rigorous coupled wave analysis (RCWA). A Lippmann-Schwinger equation is constructed including the Green's function, zero-th order wave function and a perturbation function. The Lippmann-Schwinger equation is then evaluated over a selected set of mesh points within the perturbation domain. The resulting linear equations are solved to compute one or more reflection coefficients for the subject.
A method for modeling optical scattering includes an initial step of defining a zero-th order structure (an idealized representation) for a subject including a perturbation domain and a background material. A Green's function and a zero-th order wave function are obtained for the zero-th order structure using rigorous coupled wave analysis (RCWA). A Lippmann-Schwinger equation is constructed including the Green's function, zero-th order wave function and a perturbation function. The Lippmann-Schwinger equation is then evaluated over a selected set of mesh points within the perturbation domain. The resulting linear equations are solved to compute one or more reflection coefficients for the subject.
Methods and apparatus for monitoring oxygen saturation levels in tissue are disclosed. According to one aspect of the present invention, a sensor arrangement for use in an optical imaging system includes a first source structure, a second source structure, and a detector arrangement. The first source structure provides a first beam of light and the second source structure provides a second beam of light. The detector arrangement includes detector structures that have centerpoints, and receives the first and second beams of light after the first and second beams of light are reflected off of an external surface. The detector arrangement is arranged to define a first axis that passes through the centerpoint of each detector structure, and a distance from a centerpoint of the first source structure to the first axis is not equal to a distance from a centerpoint of the second source structure to the first axis.
There is provided a method and a system for determining the concentration of chromophores and reconstructing images in turbid media, such as animal tissues, using a continuous wave optical approach. In particular the approach is based on measurements of attenuation signals and the calculation of concentrations of chromophores using a predetermined scatter law. The system comprises a continuous wave photon migration model calculator coupled to an optical source and detector for estimating concentrations of chromophores and scatter parameters used in image reconstruction.
