Hull E L, Nichols M G, Foster T H
Department of Physics and Astronomy, University of Rochester, NY 14627, USA.
Phys Med Biol. 1998 Nov;43(11):3381-404. doi: 10.1088/0031-9155/43/11/014.
We report the use of steady-state diffuse reflectance spectroscopy (SSDRS) to measure the near-infrared absorption spectrum of liquid phantoms containing human erythrocytes in aqueous suspensions of polystyrene spheres which simulate the scattering properties of tissue. The absorption spectra obtained from these SSDRS measurements of intact red cells under oxygenated and deoxygenated conditions are compared with several published spectra of 'stripped' haemoglobin prepared from lysed cells. Two fitting algorithms (nonlinear least squares and singular value decomposition) which exploit the broad spectral range provided by these measurements (170 data points spanning 164 nm in a single acquisition) are used to determine haemoglobin oxygen saturation (SO2) from SSDR spectra collected over a wide range of measured oxygen partial pressures. The validity of these algorithms is assessed by comparing literature values of p50 (the oxygen tension at which haemoglobin is 50% saturated) and the Hill coefficient to values of these parameters determined from the SO2 estimates. The singular value decomposition algorithm can also be used to reconstruct the non-haemoglobin background absorption spectrum without a priori assumptions regarding its constituent chromophores or their concentrations. Using this technique, the absorption spectrum of a small amount of India ink (maximum absorption coefficient (mu(a max)) approximately 0.0006 mm(-1)) added to a phantom containing red cells (mu(a max) approximately 0.026 mm(-1)) was reconstructed over a full range of oxygen saturations. The implications of these measurements for detection of weakly absorbing chromophores (such as cytochrome aa3) in the presence of haemoglobin are discussed.
我们报告了使用稳态漫反射光谱法（SSDRS）来测量聚苯乙烯球体水悬浮液中含有人红细胞的液体模型的近红外吸收光谱，该悬浮液模拟了组织的散射特性。将在氧合和脱氧条件下对完整红细胞进行这些SSDRS测量所获得的吸收光谱，与从裂解细胞制备的“剥离”血红蛋白的几个已发表光谱进行比较。利用这些测量提供的宽光谱范围（单次采集跨越164 nm的170个数据点）的两种拟合算法（非线性最小二乘法和奇异值分解），用于根据在广泛测量的氧分压范围内收集的SSDR光谱确定血红蛋白氧饱和度（SO2）。通过将p50（血红蛋白50%饱和时的氧张力）和希尔系数的文献值与从SO2估计值确定的这些参数的值进行比较，评估这些算法的有效性。奇异值分解算法还可用于重建非血红蛋白背景吸收光谱，而无需对其组成发色团或其浓度进行先验假设。使用该技术，在整个氧饱和度范围内重建了添加到含有红细胞的模型（最大吸收系数（μa max）约为0.026 mm-1）中的少量印度墨水（最大吸收系数（μa max）约为0.0006 mm-1）的吸收光谱。讨论了这些测量对于在存在血红蛋白的情况下检测弱吸收发色团（如细胞色素aa3）的意义。
