A Novel Method for Estimating Blood Oxygen That Aims In Situ Analysis of Retinal Metabolism - Spectrum colorimetric analysis -

本研究的目的是开发一种评估血氧的方法，该方法可能在不久的将来应用于视网膜新陈代谢的原位测量。下面简要回顾了一些专题结果。为了同时测量血管上方和周围组织的光谱反射率，利用双式多道光谱仪和计算机构建了一种测量装置。提出了一种用CIEXYZ比色系统的主导波长和激发纯度来分析光谱反射率的新方法。根据该方法，开发了静脉和动脉的分析软件，并成功地用于静脉和动脉的识别。利用蒙特卡罗方法产生不同条件下的光谱反射率数据，尝试从主导波长推导出血氧饱和度。计算结果给出了饱和度的粗略估计，但其质量还不够。为了估计饱和度的绝对值，研究了一种不同的方法，使用多元回归分析和蒙特卡罗模拟相结合。结果提高了估计的准确率。通过对Intralipid溶液、色素和血液组成的体模模型的实验，验证了该方法的有效性。在频谱有噪声的情况下进行了错误的估计。为了将所提出的方法应用于视网膜氧饱和度测量，新引入了一种使用参考表的方法，该方法直接从光谱中给出氧饱和度。开发了遵循该方法的软件。为了验证该方法的可行性，对已知参数的样品进行了实验。用该方法成功地利用测得的反射光谱估算了血氧饱和度。弱光强度的测量仍然存在明显的误差，但在通常情况下，结果是可以接受的。

The purpose of this study is to develop a method for evaluating blood oxygen, which may be applied in the near future to in situ measurements of retinal metabolism. Some topical results are briefly reviewed below.1. To measure spectral reflectances above a blood vessel and on the surrounding tissue simultaneously, a measuring apparatus was constructed by using a dual-type multi-channel spectrometer and computer.2. A new method was proposed for analysis of spectral reflectances in terms of the dominant wavelength and the excitation purity in the CIEXYZ colorimetric system. According to this method, the analyzing software was developed and successfully used for discriminating between vein and artery.3. By producing spectral reflectance data with various conditions by using the Monte Carlo method, a derivation of oxygen saturation from the dominant wavelength was tried. The result gives rough estimation of the saturation but its quality was not enough.4. To estimate an absolute value of the saturation, a different approach was investigated by using the multiple regression analysis combined with the Monte Carlo simulation. The result improved the estimation.5. The usefulness of this method was verified by experiments with phantom models consisting of the Intralipid solution, pigments and blood. Erroneous estimation was made in case of spectra having noises.6. To apply the proposed method to retinal oxymetry, a method using a reference table that gives directly the oxygen saturation from spectra was newly introduced. The software which follows this method was developed.7. To verify the feasibility of this method, experiments were conducted for samples with known parameters. Measured reflectance spectra were successfully used to estimate the oxygen saturation by using the present method. Measurements with weak light-intensity still suffer from significant errors, but in usual cases results are acceptable.