传感器几何结构对近红外组织氧合检测仪灵敏度的影响

The Influence of Probe Geometry on the Sensitivity of Tissue Oximeter Using near Infra-red Spectroscopy

近红外组织氧合检测仪基于强散射条件下修正的朗伯 比耳吸收定律 ,通过连续记录多个近红外波长下光密度随生理状态的变化 ,从而可达到对人体组织中光的吸收体 (氧合血红蛋白 ,还原血红蛋白 ,细胞色素氧化酶等 )浓度变化的定量检测。本文利用蒙特卡罗仿真方法对光在多层生物组织模型中的平均穿透深度、光子平均飞行距离和空间灵敏度分布进行了仿真 ,结果表明 ,传感器几何结构 ,即光源与光检测器之间的距离是影响检测灵敏度的重要因素 ,适当增加这一距离有助于深层组织生化信息的提取和测量灵敏度的提高 ,但是它又受到信噪比降低的限制。针对特定的组织部位 ,存在着最优的光源～探测器距离。

Based on the modified Lambert Beer law under scattering media,near infra red spectroscopy tissue oximeter measures the changes of absorber concentrations (such as oxy hemoglobin,deoxy hemoglobin,cytochrome aa3).This is made possible by recording the optical density change under different physiological status.This paper describes the average penetration depth,average photon pathlength and spatial sensitive profile in multi layered tissue model using Monte Carlo method.The result shows the probe geometry of the sensor,which is the separation between the light source and the detector,has a great influence on the sensitivity of measurement.Increasing this separation properly allows the improvement of the sensitivity of measurement and the increase of the probability of looking at oxygenation deep under the surface tissue.But this improvement is limited by the decrease of signal noise ratio.Optimum probe spacing should be estimated for special tissue structure.