The recovery of the absorption spectra of oxy- and deoxyhemoglobin from the coefficients of diffuse transmission and reflection of whole blood

Wavelength selection in measuring red blood cell aggregation based on light transmittance

“…Hemoglobin is an effective light absorbant, especially at wavelengths below 600 nm. 17,27,28 Thus, absorbance of hemoglobin has a wellknown dependence on the wavelength of light and this dependency perfectly explains the relationship between the level of transmittance and wavelength observed in this study: about 10 times higher absorbance at wavelengths below 600 nm, 27 which is consistent with the differences in the LT shown in Fig. 2.…”

“…At wavelengths away from the isobestic points between 600 and 800 nm, deoxyhemoglobin has a higher absorbance, yielding a ∼10-fold difference compared to oxyhemoglobin at ∼650 nm, 27 with this difference reflected by parameters sensitive to transmitted light intensity (Table 1). Differences between oxygenated and hypoxic samples decreased with wavelength and were negligible for measurements at 800 nm (i.e., close to the isosbestic point), 28,29 indicating that using a light source of ∼800 nm wavelength may eliminate the influence of oxygenation on these parameters.…”

“…Hemoglobin has isobestic points for oxygenated and deoxygenated forms (e.g., 582 and 808 nm), with the largest difference in light absorbance between these forms at about 650 nm. 28,29 LT spectra were recorded during flow, immediately after flow stoppage, and 60 s after flow stoppage using oxygenated and hypoxic aliquots of the blood samples (Fig. 3).…”

“…Nevertheless, our observations indicate that RBC aggregation measurements should include standardization of oxygenation level in the samples (e.g., equilibration of the samples with ambient air to achieve ∼100% hemoglobin oxygen saturation) even if the syllectogram recordings are done using a light source with a wavelength near an isosbestic point (i.e., ∼800 nm). 28,29 Hemoglobin oxygen saturation may significantly differ between samples used for assessing RBC aggregation unless a specific procedure is used for standardization of oxygenation; lack of standardization is expected to contribute to enhanced variance of measured data within a group, thereby influencing the statistical power of a parameter. Note that the dependence of aggregation parameters on oxygenation status has been reported for instruments using light sources in the 600-to 700-nm range, but not for instruments using light sources in the infrared range.…”

Hybrid reflected‐ultrasound computed tomography versus B‐mode‐ultrasound for muscle scoring in spinal muscular atrophy

“…These light-and sound-based technologies use reflected pressure waves from endogenous absorbers to detect and quantify tissue components. 2,3 For example, hemoglobin is one of the dominant absorbers in the near-infrared window of light with a robust absorption at single wavelength 800 nm [4][5][6][7] as well as by multispectral absorption patterns. 8,9 Multispectral optoacoustic tomography (MSOT) uses multiwavelength laser tissues and has implemented reflected-ultrasound computed tomography (RUCT) for anatomical guidance.…”