John M. Steinke

Bio: John M. Steinke is an academic researcher from University of Texas Health Science Center at San Antonio. The author has contributed to research in topics: Light scattering & HEMOGLOBINOMETER. The author has an hindex of 10, co-authored 15 publications receiving 633 citations. Previous affiliations of John M. Steinke include University of Texas System.

Comparison of Mie theory and the light scattering of red blood cells

Abstract: Two important optical properties of red blood cells (RBCs), their microscopic scattering cross sections sigma(s), and the mean cosine of their scattering angles micro, contribute to the optical behavior of whole blood. Therefore, the ability of Mie theory to predict values of sigma(s) and was tested by experiment. In addition, the effect of red blood cell size on sigma(s) and micro was investigated in two ways: (1) by studying erythrocytes from the dog, goat, and human, three species known to have different RBC sizes and (2) by allowing the RBCs from each species to shrink or swell osmotically. Values of sigma(s) obtained by measuring the collimated transmittance of dilute RBC suspensions illuminated with a He-Ne laser agreed with those predicted by Mie theory. Moreover, measured as values were directly proportional to RBC volume. By contrast, values of from Mie theory were consistently greater than those obtained experimentally by making angular scattering measurements in a goniometer. Thus Mie theory appears to yield adequate values for the RBC's microscopic scattering cross section, but by treating the RBC as a sphere with an equal volume, Mie theory fails to take the RBC's anisotropy into account and thus yields spuriously high values for micro.

Method and apparatus for direct spectrophotometric measurements in unaltered whole blood

Abstract: A method and apparatus which allow accurate spectrophotometric determinations of the concentrations of various hemoglobin species in whole blood without hemolysis or dilution. To overcome complex optical properties of whole blood, the invention employs 1) an optical apparatus (10, 11, 12, 13 and 14), designed to maximize the true optical absorbance of whole blood and to minimize the effects of light scattering on the spectrophotometric measurements of concentrations of various constituent components, and 2) methods to correct the hemoglobin concentration measurements for light scattering and for the effects of the finite bandwidth of the substantially monochromatic light. In the optical apparatus, (10-14), (including an optical cuvette (11)) all optical parameters, such as sample thickness, detector size and shape, sample to detector distance, wavelengths, monochromicity, maximum angle of light capture by detector, are optimal values to minimize the contribution of light scattering to the total optical attenuation of unaltered whole blood and maximize contribution of true optical absorbance.

Diffusion model of the optical absorbance of whole blood.

Abstract: Photon-diffusion theory has had limited success in modeling the optical transmittance of whole blood. Therefore we have developed a new photon-diffusion model of the optical absorbance of blood. The model has benefited from experiments designed to test its fundamental assumptions, and it has been compared extensively with transmittance data from whole blood. The model is consistent with both experimental and theoretical notions. Furthermore, when all parameters associated with a given optical geometry are known, the model needs no variational parameters to predict the absolute transmittance of whole blood. However, even if the exact value of the incident light intensity is unknown (which is the case in many situations), only a single additive constant is required to scale experiment to theory. Finally, the model is shown to be useful for simulating scattering effects and for delineating the relative contributions of the diffuse transmittance and the collimated transmittance to the total optical density of whole blood. Applications of the model include oximetry and measurements of the arteriovenous oxygen difference in whole, undiluted blood.

Role of Light Scatterng in Whole Blood Oximetry

Abstract: We investigated the role of light scattering in whole blood oximetry by transmission spectrophotometry. To delineate the role of scattering and absorbance in the measurement of oxyhemoglobin saturation, we applied Twersky's theory of radiation scattering and measured the apparent optical density of whole blood and hemoglobin solutions. The optical density versus hematocrit relationship predicted by Twersky's theory was found to give a good fit to the data obtained at 660, 813, 880, and 940 nm. A semi-empirical variation of Twersky's equation and photon diffusion equations were also compared to the data, and Twersky's original equation was found to give the best fit. Therefore, Twersky's equation was employed throughout the rest of the data analysis. Total scattering effects were shown to be wavelength and oxygenation dependent. Moreover, the relationship between total scattering effects and percent O2 saturation was approximately linear, and it had a greater slope (at 660 nm) than absorbance versus O2 saturation. Thus, scattering effects in the red-infrared range do not detract from the linearity of whole blood oximeters. By contrast, scattering effects increase the sensitivity of oximeters by contributing linearly to the total O. D. change that occurs with altered oxygenation.

Effects of temperature on optical absorbance spectra of oxy-, carboxy-, and deoxyhemoglobin.

Abstract: The optical absorbance spectra of oxy-, carboxy-, and deoxyhemoglobin were recorded at wavelengths from 479 to 651 nm and at temperatures of 20, 30, and 40 degrees C. As noted in earlier reports, a major effect of lowering the temperature was an increase in the absorptivities at or near the absorbance maxima. However, at other wavelengths, reducing the temperature increased, decreased, or caused no change in absorbance. At wavelengths where temperature-induced shifts did occur, the absorbance change appeared to be a linear function of temperature. Unlike previous reports, the data presented here are quantitative and thus can be used to predict temperature-induced errors in spectrophotometric measurements of the relative concentrations of these hemoglobin species. Examples are given of the error that would occur in a widely used CO-Oximeter, the IL482, if it were not temperature controlled. Thus, the data presented here should be particularly useful to the operators and designers of spectrophotometric instruments such as oximeters, CO-Oximeters, and hemoglobinometers.

A review of the optical properties of biological tissues

Abstract: The known optical properties (absorption, scattering, total attenuation, effective attenuation, and/or anisotropy coefficients) of various biological tissues at a variety of wavelengths are reviewed. The theoretical foundations for most experimental approaches are outlined. Relations between Kubelka-Munk parameters and transport coefficients are listed. The optical properties of aorta, liver, and muscle at 633 nm are discussed in detail. An extensive bibliography is provided. >

Time resolved reflectance and transmittance for the non-invasive measurement of tissue optical properties.

Abstract: When a picosecond light pulse is incident on biological tissue, the temporal characteristics of the light backscattered from, or transmitted through, the sample carry information about the optical absorption and scattering coefficients of the tissue. We develop a simple model, based on the diffusion approximation to radiative transfer theory, which yields analytic expressions for the pulse shape in terms of the interaction coefficients of a homogeneous slab. The model predictions are in good agreement with the results of preliminary in vivo experiments and Monte Carlo simulations.

Quantitative optical spectroscopy for tissue diagnosis

Abstract: The interaction of light within tissue has been used to recognize disease since the mid-1800s. The recent developments of small light sources, detectors, and fiber optic probes provide opportunities to quantitatively measure these interactions, which yield information for diagnosis at the biochemical, structural, or (patho)physiological level within intact tissues. However, because of the strong scattering properties of tissues, the reemitted optical signal is often influenced by changes in biochemistry (as detected by these spectroscopic approaches) and by physiological and pathophysiological changes in tissue scattering. One challenge of biomedical optics is to uncouple the signals influenced by biochemistry, which themselves provide specificity for identifying diseased states, from those influenced by tissue scattering, which are typically unspecific to a pathology. In this review, we describe optical interactions pursued for biomedical applications (fluorescence, fluorescence lifetime, phosphorescence, and Raman from cells, cultures, and tissues) and then provide a descriptive framework for light interaction based upon tissue absorption and scattering properties. Finally, we review important endogenous and exogenous biological chromophores and describe current work to employ these signals for detection and diagnosis of disease.

Optical Properties of Circulating Human Blood in the Wavelength Range 400-2500 nm.

Abstract: Knowledge about the optical properties μa,μs, and g of human blood plays an important role for many diagnostic and therapeutic applications in laser medicine and medical diagnostics. They strongly depend on physiological parameters such as oxygen saturation, osmolarity, flow conditions, haematocrit, etc. The integrating sphere technique and inverse Monte Carlo simulations were applied to measure μa,μs, and g of circulating human blood. At 633 nm the optical properties of human blood with a haematocrit of 10% and an oxygen saturation of 98% were found to be 0.210±0.002 mm-1 for μa,77.3±0.5 mm-1 for μs, and 0.994±0.001 for the g factor. An increase of the haematocrit up to 50% lead to a linear increase of absorption and reduced scattering. Variations in osmolarity and wall shear rate led to changes of all three parameters while variations in the oxygen saturation only led to a significant change of the absorption coefficient. A spectrum of all three parameters was measured in the wavelength range 400-2500 nm for oxygenated and deoxygenated blood, showing that blood absorption followed the absorption behavior of haemoglobin and water. The scattering coefficient decreased for wavelengths above 500 nm with approximately λ-1.7; the g factor was higher than 0.9 over the whole wavelength range. © 1999 Society of Photo-Optical Instrumentation Engineers.