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Background: Raman spectroscopy is a non-invasive optical technique that can probe the molecular structure and conformation of biochemical constituents. The probability of Raman scattering is exceedingly low (∼10−10), and consequently up to now the practical application of Raman spectroscopy to clinical medicine has been limited by either the weak spectral signal or by the long data acquisition times. Recent advances in Raman hardware and probe design have reduced spectral acquisition times, paving the way for clinical applications. Methods: We present an integrated real-time Raman spectroscopy system for skin evaluation and characterization, which combines customized hardware features and software implementation. Real-time data acquisition and processing includes CCD dark-noise subtraction, wavelength calibration, spectral response calibration, intensity calibration, signal saturation detection, cosmic ray rejection, fluorescence background removal, and composition modeling. Real-time in vivo Raman measurement of volar forearm skin is presented to illustrate the methods and modeling. Results: The system design implemented full-chip vertical hardware binning to improve the signal-to-noise ratio by 16-fold. The total time for a single in vivo measurement with analysis can be reduced to 100 ms with this implementation. Human skin was well modeled using the base Raman spectra. Conclusion: In vivo real-time Raman can be a very promising research and practical technique for skin evaluation. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has been used as a sensitive tool for studying biological tissue and evaluating disease. In many applications, microscopic level resolution spectral analysis is desirable. And this has been performed mostly by expensive commercial confocal micro-Raman systems. In this research, we present a simple method for building an economical and modular Raman microspectroscopy system that combines a microscope with a Raman spectrometer using an optical fiber bundle. The bundle with a circular collection end is positioned at an image plane of the microscope to collect Raman signals from the interested micro-location on the sample. The light delivery end is specially configured so that its 37 fibers are arranged along a straight line to fit into the spectrometer entrance slit. This configuration improves light collection efficiency and maintains high spectral resolution. To battle the great background autofluorescence and Raman signals that could originate from the microscope slides and optics due to the non-confocal set-up of our simplified system, conventional normal-incident illumination is replaced by oblique illumination at 45° degrees and the microscope slides are coated with gold. We demonstrated the usefulness of the system by measuring micro-Raman spectra from different skin layers on vertical sections of normal skin tissue samples. [ABSTRACT FROM AUTHOR]

Abstract: Melanin content and distribution in skin were studied by examining a patient with white, brown and blue skin tones expressed on skin affected by vitiligo. Both diffuse reflectance and autofluorescence spectra of the three distinction skin sites were measured and compared. Monte Carlo simulations were then performed to help explain the measured spectral differences. The modeling is based on a six-layer skin optical model established from published skin optical parameters and by adding melanin content into different locations in the model skin. Both the reflectance and fluorescence spectra calculated by Monte Carlo (MC) simulation were approximately in agreement with experimental results. The study suggests that: (1) trichrome vitiligo skin may be an ideal in vivo model for studying the effect of skin melanin content and distribution on skin spectroscopy properties. (2) Based on the skin optical model and MC simulation, the content and distribution of melanin in skin, or other component of skin could be simulated and predicted. (3) Both reflectance and fluorescence spectra provided information about superficial skin structures but fluorescence spectra are capable of providing information from deeper cutaneous structures. (4) The research method, including the spectral ratio method, the method of adding and modifying the melanin content in skin optical models, and MC simulation could be applied in other non-invasive optical studies of the skin. [Copyright &y& Elsevier]

Summary: Background and Purpose: Although cutaneous autofluorescence has been utilized for evaluation of skin conditions, there is a paucity of data on normal human skin autofluorescence and its dependence on anatomical site. The objective of this study is to use excitation‐emission matrix spectroscopy to quantify and characterize skin autofluorescence at different body sites. Methods: Ten anatomical sites from 30 healthy volunteers were measured with a double‐grating excitation‐emission matrix spectrofluorometer. Results: For the 10 body sites evaluated, there were four overall patterns of autofluorescence: skin from the head and neck exhibits high superficial and low bilayer fluorescence; the dorsal forearm and dorsal hand have both low superficial and bilayer fluorescence; the upper inner arm and back have high superficial and intermediate bilayer fluorescence; while the palm and thumbnail have both high superficial and bilayer fluorescence. The corresponding fluorescence excitation‐emission peaks for these patterns were as follows: head and neck, 3 peaks at 290‐300/330‐350, 360‐380/460‐485, and 380‐420/610‐630 nm; dorsal forearm and dorsal hand, 2 peaks around 295‐300/345‐360 and 385‐395/460‐485 nm; upper inner arm and back, 3 peaks around 295‐300/335‐355, 335‐340/390‐410, and 375‐390/455‐480 nm; palm and thumbnail, 3 peaks around 285‐300/345‐355, 335‐345/390‐410, and 365‐390/450‐480 nm. Conclusion: Cutaneous fluorescence varies in distinct patterns according to anatomical site, due to the component fluorophores present, skin thickness, and the degree of melanization and long term sun exposure. These EEM patterns for normal skin should be accounted for when interpreting fluorescence signals from disease states and can also be used to guide the selection of optimal wavebands when applying this optical modality. [ABSTRACT FROM AUTHOR]

One challenge in facing the application of biomedical Raman spectroscopy is that the Raman signal is acquired in a dark operation room. It is inconvenient for both the operator and the patient because it is difficult for the operator to accurately and precisely locate the target in the dark environment, and the patient feels uncomfortable in such a setting. In this note, we propose a method to implement biomedical Raman measurement with an illumination source, by multiple filtering of the illumination and the collection optics. Experimental results are demonstrated on skin Raman measurement under 785-nm excitation. [ABSTRACT FROM AUTHOR]

In evaluating the autofluorescence properties of normal and diseased skin we discovered that psoriatic plaques can emit a distinct red fluorescence when illuminated with UVA or blue light. Using a macrospectrofluorometer equipped with a 442 nm excitation laser, a sharp in vivo fluorescence emission peak around 635 nm could be demonstrated within the plaques of 34 of 75 (45%) patients with psoriasis. This peak was absent from normal appearing skin of psoriatic patients and also from the skin of 66 patients with other dermatologic diseases. A microspectrofluorometer coupled with the same excitation laser was used to obtain emission spectra of separated epidermal sheets and dermis from plaques demonstrating macroscopic red autofluorescence. An emission peak around 635 nm was observed in all three patients thus studied, but only on spectra obtained from the epidermis. Additional spectra of vertical microscopic sections of intact psoriatic skin from five other patients revealed that the peak originated from the stratum corneum. Emission spectra from other microlocations including the mid‐epidermis and dermis of psoriatic and normal skin, as well as the stratum corneum of normal skin, failed to demonstrate a 635 nm peak. The excitation and emission fluorescence spectra of acid extracts of psoriatic scale from five patients were all similar to those of protoporphyrin IX in acid solution. High performance liquid chromatography identified the presence of protoporphyrin IX in the acid extracts from psoriatic scale of the same patients. We conclude that native psoriatic plaques can exhibit red autofluorescence that is due to elevated levels of protoporphyrin IX within scales. [ABSTRACT FROM AUTHOR]