Search

While histopathology of excised tissue remains the gold standard for diagnosis, several new, non-invasive diagnostic techniques are being developed. They rely on physical and biochemical changes that precede and mirror malignant change within tissue. The basic principle involves simple optical techniques of tissue interrogation. Their accuracy, expressed as sensitivity and specificity, are reported in a number of studies suggests that they have a potential for cost effective, real-time, in situ diagnosis. We review the Third Scientific Meeting of the Head and Neck Optical Diagnostics Society held in Congress Innsbruck, Innsbruck, Austria on the 11th May 2011. For the first time the HNODS Annual Scientific Meeting was held in association with the International Photodynamic Association (IPA) and the European Platform for Photodynamic Medicine (EPPM). The aim was to enhance the interdisciplinary aspects of optical diagnostics and other photodynamic applications. The meeting included 2 sections: oral communication sessions running in parallel to the IPA programme and poster presentation sessions combined with the IPA and EPPM posters sessions. © 2011 Jerjes et al; licensee BioMed Central Ltd.

The complete surgical removal of disease is a desirable outcome particularly in oncology. Unfortunately much disease is microscopic and difficult to detect causing a liability to recurrence and worsened overall prognosis with attendant costs in terms of morbidity and mortality. It is hoped that by advances in optical diagnostic technology we could better define our surgical margin and so increase the rate of truly negative margins on the one hand and on the other hand to take out only the necessary amount of tissue and leave more unaffected non-diseased areas so preserving function of vital structures. The task has not been easy but progress is being made as exemplified by the presentations at the 2nd Scientific Meeting of the Head and Neck Optical Diagnostics Society (HNODS) in San Francisco in January 2010. We review the salient advances in the field and propose further directions of investigation. © 2011 Upile et al; licensee BioMed Central Ltd.

We describe a system capable of measuring spatially resolved reflectance spectra from 380 to 950 nm and fluorescence excitation emission matrices from 330 to 500 nm excitation and 380 to 700 nm emission in vivo. System performance was compared to that of a standard scanning spectrofluorimeter. This 'FastEEM' system was used to interrogate human normal and neoplastic oral cavity mucosa in vivo. Measurements were made through a fiber-optic probe and require 4 min total measurement time. We present a method based on autocorrelation vectors to identify excitation and emission wavelengths where the spectra of normal and pathologic tissues differ most. The FastEEM system provides a tool with which to study the relative diagnostic ability of changes in absorption, scattering, and fluorescence properties of tissue.

Background and objectiveThis paper compares the ability of three analytic techniques to predict chromophore concentration from fluorescence emission spectra of homogeneous, turbid samples with optical properties similar to human tissue.Study design, materials and methodsTwo models of light propagation were implemented (exponential attenuation, two flux Kubelka-Munk theory); a priori information about sample optical properties was used to analyze data with the two flux Kubelka-Munk model. The third data analysis technique utilizes the method of partial least squares (PLS) to develop an empirical, linear model of sample fluorescence from a training set with optical properties and known concentrations representative of those to be predicted. This model can be applied to predict chromophore concentrations in the unknown samples.ResultsOf the three methods, PLS achieved the most accurate results and was able to predict fluorophore concentration to within +/- 6% of true values.ConclusionWe investigated conditions under which PLS predictions were most accurate and find that best results are achieved when predictions are based on fluorescence emission spectra at more than one excitation wavelength with inclusion of the tail of Rayleigh scattering at the excitation wavelength.

We present a method to extend rank-annihilation-factor analysis (RAFA) for the analysis of fluorescence from homogeneous turbid samples. The method is based on a fundamental relationship between the fluorescence of a dilute solution and that of a turbid solution. We have derived this relationship, known as the transfer function, for turbid materials using the two-flux Kubelka-Munk theory. The method is tested with spectroscopic data from optically thin and turbid samples of the media of a human aorta. At 450-nm excitation, agreement between the measured and predicted dilute-solution fluorescence spectra is within 5% at all emission wavelengths; at 340-nm excitation, agreement is within 20% at all wavelengths, with some residual Soret-band absorption. The simulations presented indicate that the transfer function is markedly more sensitive to absorption than to scattering properties.

We describe a fiber-optic-based confocal fluorescence spectrometer for obtaining depth-resolved, attenuated fluorescence emission spectra with lateral resolution of several microns and depth resolution of tens of microns. The confocal optics of the spectrometer are small, inexpensive, and easy to construct and to interface to existing spectrometers. We compare the performance of this system to that of conventional fluorescence spectrometers for nonscattering homogeneous and inhomogeneous samples. We demonstrate that the confocal measurements readily provide information about the sample geometry and optical properties not available from nonconfocal measurements. Potential applications of the technique are discussed.

This paper presents a phantom which simulates the optical properties of tissue. The phantom absorption coefficient, scattering coefficient, anisotropy factor, and fluorescence quantum yield can be independently varied to investigate the effects of these parameters on fluorescence excitation and emission spectra from 300 to 650 nm. Phantom fluorophores include Flavin Adenine Dinucleotide (FAD) and Rhodamine B. Absorption is controlled by adjusting phantom hemoglobin concentration. On the basis of their smoothly varying scattering coefficient and the relatively low amount of fluorescence contributed to the mixture in comparison to other available scatterers, 1.05-ttm-diameter polystyrene microspheres were selected as a scatterer. Sample inhomogeneities are simulated by preparing the phantom in a gelatin substrate. The optical properties of turbid phantoms determined with the use of indirect techniques agree well with known values as long as μ(1 - g) > μ. Data are presented from dilute, absorbing, and turbid phantoms and inhomogeneous phantoms to qualitatively illustrate the effects of optical properties and sample geometry on fluorescence spectra. The phantom provides the framework for detailed quantitative investigations of the effects of optical properties, sample size, shape, and structure, boundary conditions, and collection geometry on fluorescence spectra. © 1993 Society for Applied Spectroscopy.