Inverse method 3-D reconstruction of localized in vivofluorescence-application to Sjogren syndrome

摘要

The development of specific fluorescently labeled cell surfacenmarkers have opened the possibility of specific and quantitativennoninvasive diagnosis of tissue changes. We are developing anfluorescence scanning imaging system that can perform an“noninvasive optical biopsy” of the Sjogren syndrome (SS)nwhich may replace the currently used histological biopsy. The diagnosisnof SS is based on the quantification of the number of topicalnpreadministered fluorescent antibodies which specifically bind to thenlymphocytes infiltrating the minor salivary glands. We intend to scannthe lower lip, and for each position of the scan, generate antwo-dimensional (2-D) image of fluorescence using a charge-coupledndevice (CCD) camera. We have shown previously that our diffusenfluorescent photon migration theory predicts adequately the positionsnand strengths of one and two fluorescent targets embedded at differentndepths in tissue-like phantoms. An inverse reconstruction algorithmnbased on our theoretical findings has been written in C++ andnuses 2-D images to predict the strength and location of embeddednfluorophores. However, due to large numbers of variables, which includenthe optical properties of the tissue at the excitation and emissionnwavelengths, and the positions and strengths of an unknown number ofnfluorophore targets, the validity of the final result depends onnassumptions (such as the number of targets) and the input values for thenoptical parameters. Our results show that the number of fluorophorentargets reconstructed for each scan is limited to two, and at least thenscattering coefficient at the excitation wavelength is needed a priorinto obtain good results. The latter can be obtained by measurements ofnspatially resolved diffuse reflectance at the excitation wavelength thatnprovides the product of the absorption and scattering coefficients