A portable scanning reflectance spectrophotometer using visible wavelengths for the rapid measurement of skin pigments

Abstract

A portable rapid scan reflectance spectrometer (400-700 nm in 2.8 s) has been developed for the measurement of cutaneous pigments. The instrument incorporates a tungsten halogen lamp light source, light transmission by fibre optics and wavelength selection by a circular variable wavelength interference filter. A microcomputer controls the instrument and processes the data. The performance of the instrument was evaluated by undertaking in vitro measurements of the reflectance spectra of blood. An index of the haemoglobin content of the sample based on the gradients of the log inverse reflectance spectrum between isobestic points at 527.5, 544 and 573 nm was devised and shown to be independent of the oxygenation of the haemoglobin. The haemoglobin index was combined with measurements at 558.5 nm, a wavelength at which absorbance is sensitive to the oxygenation of haemoglobin, to give a measure of oxygen saturation. The parameter was validated by determining the oxygen dissociation curve of red cells in plasma in vitro at pH 7.33, 37 degrees C and under a partial pressure of 40 mmHg of CO2.

Noninvasive imaging of human skin hemodynamics using a digital red-green-blue camera

“…The average values of C m and C tb were 4.3 ± 1.2% and 1.1 ± 0.4%, respectively, in preocclusion (control), which are close to typical values reported in the literature. 2,11,13 The average value of 71 ± 16% for SO 2 in pre-occlusion is lower than typical arterial SO 2 , which ranges from 90% to 98%. Typical value of venous SO 2 is almost 60%.…”

“…Diffuse reflectance spectroscopy has been widely used for the evaluation of human skin chromophores at a single location. [1][2][3][4][5][6][7][8][9][10] The multispectral imaging technique is a useful tool for extending diffuse reflectance spectroscopy to spatial mapping of the chromophores in skin tissue. This can be simply achieved by a monochromatic CCD camera with narrow band filters and a white light source, which has been used to investigate the hemoglobin perfusion in living tissue.…”

Interface pressure and cutaneous hemoglobin and oxygenation changes under ischial tuberosities during sacral nerve root stimulation in spinal cord injury

“…After data acquisition, the data were converted to ASCII text and exported to Microsoft Excel 2000 (Microsoft Corporation, Redmond, Washington). IHB and IOX were calculated with a modified version of methods by Feather et al [31][32] and Hagisawa et al [28]. Equations for the calculation of IHB and IOX for this study were where A is the absorption value at the specified wavelength (nanometer) in the TRS.…”

Feasibility Study of Optical Spectroscopy as a Medical Tool for Diagnosis of Skin Lesions

“…Skin color measurement through reflectance spectroscopy has received significant attention in the literature [19] [26][27] [28]. It has been used to provide a numerical index for color, which in turn allows for the study of constriction of a blood vessel and abnormal redness of the skin due to local congestion, such as in inflammation [29].…”