Chance B, Leigh J S, Miyake H, Smith D S, Nioka S, Greenfeld R, Finander M, Kaufmann K, Levy W, Young M
Department of Biochemistry, University of Pennsylvania, Philadelphia 19104.
Proc Natl Acad Sci U S A. 1988 Jul;85(14):4971-5. doi: 10.1073/pnas.85.14.4971.
Continuous (CW) and pulsed light were used for the noninvasive measurement of hemoglobin oxygenation in tissues. A dual wavelength method of continuous illumination spectroscopy used 760 nm (deoxyhemoglobin peak) and 800 nm (an oxyhemoglobin-deoxyhemoglobin isosbestic point) to measure the kinetics and extent of oxyhemoglobin deoxygenation in brains during mild ischemia/hypoxia. Absorption and scattering were modeled in an artificial milk/yeast blood system, which gave an exponential relationship between absorption and optical path length to a depth of 7 cm. Time-resolved spectroscopy (10-ps resolution) afforded a display of the times and distances of arrival of photons emitted by the cat brain in response to a 10-ps input pulse. The emitted photons rose to a peak in a fraction of a nanosecond and declined exponentially over a few nanoseconds. The half-time of exponential decay corresponds to photon migration over a distance of 4 cm. Exponential light emission continued for several more nanoseconds when the brain was encased by the skull, which plays a key role in prolonging light emission. The exponential decline of light intensity has a value [exp(-microL)], where L is the path length determined from the time/distance scale and mu is the characteristic of the migration of light in the brain. The factor mu is increased by increasing absorption, and mu' = epsilon C where epsilon and C are the Beer-Lambert parameters of extinction coefficient (epsilon) and concentration (C). Thus, deoxyhemoglobin can be quantified in brain tissues.
连续波（CW）光和脉冲光被用于组织中血红蛋白氧合的无创测量。连续照明光谱的双波长方法使用760纳米（脱氧血红蛋白峰）和800纳米（氧合血红蛋白 - 脱氧血红蛋白等吸收点）来测量轻度缺血/缺氧期间大脑中氧合血红蛋白脱氧的动力学和程度。在人工牛奶/酵母血液系统中对吸收和散射进行建模，该系统给出了吸收与至7厘米深度的光程长度之间的指数关系。时间分辨光谱（10皮秒分辨率）能够显示猫脑对10皮秒输入脉冲响应时发射光子的到达时间和距离。发射的光子在不到一纳秒的时间内升至峰值，并在几纳秒内呈指数下降。指数衰减的半衰期对应于光子在4厘米距离上的迁移。当大脑被颅骨包裹时，指数光发射会持续数纳秒，颅骨在延长光发射方面起关键作用。光强度的指数下降值为[exp(-μL)]，其中L是根据时间/距离尺度确定的光程长度，μ是光在大脑中迁移的特征。通过增加吸收可使因子μ增大，且μ' = εC，其中ε和C分别是消光系数（ε）和浓度（C）的比尔 - 朗伯参数。因此，脱氧血红蛋白可在脑组织中进行定量分析。
