Broadband hyperspectral imaging for breast tumor detection using spectral and spatial information

Complete tumor removal during breast-conserving surgery remains challenging due to the lack of optimal intraoperative margin assessment techniques. Here, we use hyperspectral imaging for tumor detection in fresh breast tissue. We evaluated different wavelength ranges and two classification algorithms; a pixel-wise classification algorithm and a convolutional neural network that combines spectral and spatial information. The highest classification performance was obtained using the full wavelength range (450-1650nm). Adding spatial information mainly improved the differentiation of tissue classes within the malignant and healthy classes. High sensitivity and specificity were accomplished, which offers potential for hyperspectral imaging as a margin assessment technique to improve surgical outcome. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Method for coregistration of optical measurements of breast tissue with histopathology : the importance of accounting for tissue deformations

For the validation of optical diagnostic technologies, experimental results need to be benchmarked against the gold standard. Currently, the gold standard for tissue characterization is assessment of hematoxylin and eosin (H&E)-stained sections by a pathologist. When processing tissue into H&E sections, the shape of the tissue deforms with respect to the initial shape when it was optically measured. We demonstrate the importance of accounting for these tissue deformations when correlating optical measurement with routinely acquired histopathology. We propose a method to register the tissue in the H&E sections to the optical measurements, which corrects for these tissue deformations. We compare the registered H&E sections to H&E sections that were registered with an algorithm that does not account for tissue deformations by evaluating both the shape and the composition of the tissue and using microcomputer tomography data as an independent measure. The proposed method, which did account for tissue deformations, was more accurate than the method that did not account for tissue deformations. These results emphasize the need for a registration method that accounts for tissue deformations, such as the method presented in this study, which can aid in validating optical techniques for clinical use. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License

Estimation of biological chromophores using diffuse optical spectroscopy: benefit of extending the UV-VIS wavelength range to include 1000 to 1600 nm

With an optical fiber probe, we acquired spectra from swine tissue between 500 and 1600 nm by combining a silicon and an InGaAs spectrometer. The concentrations of the biological chromophores were estimated by fitting a mathematical model derived from diffusion theory. The advantage of our technique relative to those presented in previous studies is that we extended the commonly-used wavelength ranges of 500 and 1000 nm to include the range of 1000 to 1600 nm, where additional water and lipid absorption features exist. Hence, a more accurate estimation of these two chromophores is expected when spectra are fitted between 500 and 1600 nm than between 500 and 1000 nm. When extending the UV-VIS wavelength range, the estimated total amount of chromophores approached 100% of the total as present in the probed volume. The confidence levels of the water and lipid related parameters increases by a factor of four

Multidiameter single-fiber reflectance spectroscopy of heavily pigmented skin:modeling the inhomogeneous distribution of melanin

When analyzing multidiameter single-fiber reflectance (MDSFR) spectra, the inhomogeneous distribution of melanin pigments in skin tissue is usually not accounted for. Especially in heavily pigmented skins, this can result in bad fits and biased estimation of tissue optical properties. A model is introduced to account for the inhomogeneous distribution of melanin pigments in skin tissue. In vivo visible MDSFR measurements were performed on heavily pigmented skin of type IV to VI. Skin tissue optical properties and related physiological properties were extracted from the measured spectra using the introduced model. The absorption of melanin pigments described by the introduced model demonstrates a good correlation with the co-localized measurement of the well-known melanin index. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License

In vivo quantification of photosensitizer concentration using fluorescence differential path-length spectroscopy:influence of photosensitizer formulation and tissue location

In vivo measurement of photosensitizer concentrations may optimize clinical photodynamic therapy (PDT). Fluorescence differential path-length spectroscopy (FDPS) is a non-invasive optical technique that has been shown to accurately quantify the concentration of Foscan (R) in rat liver. As a next step towards clinical translation, the effect of two liposomal formulations of mTHPC, Fospeg (R) and Foslip (R), on FDPS response was investigated. Furthermore, FDPS was evaluated in target organs for head-and-neck PDT. Fifty-four healthy rats were intravenously injected with one of the three formulations of mTHPC at 0.15 mgkg(-1). FDPS was performed on liver, tongue, and lip. The mTHPC concentrations estimated using FDPS were correlated with the results of the subsequent harvested and chemically extracted organs. An excellent goodness of fit (R-2) between FDPS and extraction was found for all formulations in the liver (R-2 = 0.79). A much lower R-2 between FDPS and extraction was found in lip (R-2 = 0.46) and tongue (R-2 = 0.10). The lower performance in lip and in particular tongue was mainly attributed to the more layered anatomical structure, which influences scattering properties and photosensitizer distribution. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JBO. 17.6.067001

In vivo quantification of photosensitizer fluorescence in the skin-fold observation chamber using dual-wavelength excitation and NIR imaging

A major challenge in biomedical optics is the accurate quantification of in vivo fluorescence images. Fluorescence imaging is often used to determine the pharmacokinetics of photosensitizers used for photodynamic therapy. Often, however, this type of imaging does not take into account differences in and changes to tissue volume and optical properties of the tissue under interrogation. To address this problem, a ratiometric quantification method was developed and applied to monitor photosensitizer meso-tetra (hydroxyphenyl) chlorin (mTHPC) pharmacokinetics in the rat skin-fold observation chamber. The method employs a combination of dual-wavelength excitation and dualwavelength detection. Excitation and detection wavelengths were selected in the NIR region. One excitation wavelength was chosen to be at the Q band of mTHPC, whereas the second excitation wavelength was close to its absorption minimum. Two fluorescence emission bands were used; one at the secondary fluorescence maximum of mTHPC centered on 720 nm, and one in a region of tissue autofluorescence. The first excitation wavelength was used to excite the mTHPC and autofluorescence and the second to excite only autofluorescence, so that this could be subtracted. Subsequently, the autofluorescence-corrected mTHPC image was divided by the autofluorescence signal to correct for variations in tissue optical properties. This correction algorithm in principle results in a linear relation between the corrected fluorescence and photosensitizer concentration. The limitations of the presented method and comparison with previously published and validated techniques are discussed