Duncan A, Meek J H, Clemence M, Elwell C E, Fallon P, Tyszczuk L, Cope M, Delpy D T
Department of Medical Physics and Bioengineering, University College London, United Kingdom.
Pediatr Res. 1996 May;39(5):889-94. doi: 10.1203/00006450-199605000-00025.
Near infrared spectroscopy (NIRS) has been used to measure concentration changes of cerebral hemoglobin and cytochrome in neonates, children, and adults, to study cerebral oxygenation and hemodynamics. To derive quantitative concentration changes from measurements of light attenuation, the optical path length must be known. This is obtained by multiplying the source/ detector separation by a laboratory measured differential path length factor (DPF) which accounts for the increased distance traveled by light due to scattering. DPF has been measured by time of flight techniques on small populations of adults and postmortem infants. The values for adults are greater than those for newborns, and it is not clear how to interpolate the present data for studies on children. Recent developments in instrumentation using phase resolved spectroscopy techniques have produced a bedside unit which can measure optical path length on any subject. We have developed an intensity modulated optical spectrometer which measures path length at four wavelengths. Two hundred and eighty three subjects from 1 d of age to 50 y were studied. Measurements were made at a fixed frequency of 200 MHz and a source detector separation of 4.5 cm. Results suggest a slowly varying age dependence of DPF, following the relation DPF690 = 5.38 + 0.049A0.877, DPF744 = 5.11 + 0.106A0.723, DPF807 = 4.99 + 0.067A0.814, and DPF832 = 4.67 + 0.062A0.819, where DPF690 is the DPF measured at 690 nm and A is age is expressed in years from full term. There was a wide scatter of values, however, implying that ideally DPF should be measured at the time of each study.
近红外光谱技术（NIRS）已被用于测量新生儿、儿童和成人脑中血红蛋白和细胞色素的浓度变化，以研究脑氧合和血流动力学。为了从光衰减测量中得出定量的浓度变化，必须知道光程长度。这是通过将光源/探测器间距乘以实验室测量的微分光程因子（DPF）得到的，该因子考虑了由于散射导致光传播距离的增加。DPF已通过飞行时间技术在少量成人和死后婴儿群体中进行了测量。成人的值大于新生儿的值，目前尚不清楚如何对儿童研究的数据进行插值。使用相分辨光谱技术的仪器的最新进展产生了一种床边设备，它可以在任何受试者身上测量光程长度。我们开发了一种强度调制光谱仪，它可以在四个波长下测量光程长度。对283名年龄从1天到50岁的受试者进行了研究。测量在200 MHz的固定频率和4.5 cm的光源探测器间距下进行。结果表明DPF随年龄缓慢变化，遵循以下关系：DPF690 = 5.38 + 0.049A0.877，DPF744 = 5.11 + 0.106A0.723，DPF807 = 4.99 + 0.067A0.814，DPF832 = 4.67 + 0.062A0.819，其中DPF690是在690 nm处测量的DPF，A是以足月后的年龄（以年为单位）表示的年龄。然而，值的离散度很大，这意味着理想情况下，每次研究时都应测量DPF。
