Research On Noninvasive Measurement Of Human Hemoglobin By Near Infrared Spectroscopy

Human hemoglobin level is an essential basis for clinical diagnosis of anemia and other blood diseases.The conventional biochemical measurement belongs to invasive method with the pain,long analysis period,and it's difficult to achieve real-time monitoring.Above issues,to a certain extent,hinder the early prevention and timely treatment of anemia disease.Hemoglobin near infrared spectroscopy(NIRS)analytical method is nondestructive,painless and fast analysis,which makes it possible to effectively overcome the shortcomings of conventional biochemical method and be conducive to realize the screening and prevention of anemia disease.Thus,it is firmly believed as one of the most potential method for non-invasive hemoglobin measurement with high research value and social importance.To effectively solve the key problems faced by hemoglobin NIRS analytical method,such as tissue background interference,weak effective signal,we proposed a human hemoglobin NIRS non-invasive analysis program based on differential blood volume spectrum theory.The main research contents and results are as follows:(1)Considering the requirements on the instrumental time resolution,signal to noise ratio(SNR)and portable structure,we determine the scheme of optical system by LED lighting system,LVF spectroscopic system and multi-element detector array.(2)The design of high brightness,wide band and low noise LED lighting system.According to the requirements of the lighting system,such as the beam convergence,the illumination uniformity,the utilization ratio of light energy and the structural compactness,we design two kinds of lighting systems,including transmission and reflection.Between them,the uniformity of the transmission system in the effective illumination area is as high as 90%,which is beneficial for the consistency of the information about the tissue background and the blood flow volume in each spectrum.(3)The linear variable filter(LVF)is able to simplify the structure of the spectroscopic system with the advantages of small volume and large passband.Aiming to be applied in the NIRS spectrometer for hemoglobin noninvasive measurement,the thin film design scheme of the short wavelength near-infrared LVF with high dispersion is determined.For the optimized LVF,peak transmittance is higher than 97%,the resolution is about 1% CWL(center wavelength)and the cut-off depth is less than 0.1%.It can split the 620~1080 nm wide band composite light just in 12.8-mm work area.(4)The clinical experiment on noninvasive hemoglobin measurement and the research on NIR model.On the base of the optimized LED lighting system and LVF spectroscopic system,our research group develops the NIRS spectrometer with the SNR higher than 14000:1.Then this instrument is applied to collect human spectra of 93 volunteers in the anterior segment of the index finger,and the “pure” spectra without tissue background interference are extracted by differential blood volume spectrum method.Study on the quantitative analysis ability of three kinds of multivariate calibration methods,they are partial least squares(PLS),back propagation-artificial neural network(BPANN)and support vector regression(SVR).Then,further explore the effects of standardized normal variate(SNV)and normalization,two preprocess algorithms on the NIR model.Through theoretical analysis and comparison,normalized-SVR model is found to be the best model with high noninvasive analysis accuracy and stability.Due to its advantages of nonlinear regression character,stable convergence and fast parameter optimization,SVR can achieve high hemoglobin noninvasive analysis precision under complex tissue background.The prediction correlation coefficient of the model is 0.82,the standard deviation is 7.91 g/L,and the relative deviation is only about 5.44%,which basically accommodates the requirements of clinical application.Above results show that on the base of differential blood volume spectrum method,the human hemoglobin NIRS non-invasive detection scheme is feasible and effective.Combined with optimized SVR near infrared model,our NIRS spectrometer can be applied for high-precision noninvasive analysis of human hemoglobin level.