In this work, a set of photoacoustic detection system of blood was established to identify the true blood and fake blood. The time-resolved photoacoustic signals and peak-to-peak spectra of blood samples were obtained in the wavelength from 700nm to 1064nm. In experiments, five kinds of blood in total of 150 groups were used, where three kinds of blood were the animal true blood, two others were the fake blood. The experimental results demonstrated that the true and fake blood can be easily and accurately identified from the time-resolved photoacoustic signals or peak-to-peak spectra due to the overlapping of signals or spectra. To accurately identify the true and fake blood, back propagation (BP) neural network was used to supervised train the peak-to-peak values of training blood sample. The correct rate of identifying true and fake blood based on BP is 76.7%. To improve the correct rate, the particle swarm optimization (PSO) was employed to optimize the parameters of BP including weights and thresholds. Moreover, the effects of neurons number, learning rate factor, inertia weight, two acceleration factors, iteration times and training times on the correct rate were all investigated and compared with BP. Under the optimal parameters, the correct rate of BP-PSO algorithm was improved to 96.7%. Therefore, the photoacoustic spectroscopy combined with BP-PSO algorithm has the potential value in the identification of blood.
The blood is an important tissue in the human and animal body. It has significant role in the fields of bio-medical diagnosis, animal quarantine, criminal investigation, food safety, etc. However, there are some illegal cases reported about the real blood abused by fake blood recently, which seriously impact the human health and society stability. The rapid and accuracy detection of blood is very important and urgent. To achieve this aim, the photoacoustic spectroscopy was used to detect the real blood and fake one. A set of photoacoustic detection system was established based on OPO pulsed laser and focused ultrasonic detector. In experiments, 150 groups of real and fake blood samples was test, where 120 groups were used as the training samples, 30 groups were used as the test samples. The time-resolved photoacoustic signal and peak-to-peak values of all samples were captured in the wavelengths from 700-1064nm. To classify and distinguish the real and fake blood, the support vector machine (SVM) algorithm was used to train the training blood samples and test the correct rate of classification and distinction of the real and fake blood. The results show that the correct rate is 83.3% by using the SVM algorithm. To further improve the correct rate, the principal components analysis (PCA) algorithm was used to extract the characteristic information from the photoacoustic peak-to-peak values of blood samples in full wavelengths. The correct rates of real and fake blood based on PCA-SVM algorithm under the different principal components were obtained and compared. The results show that the correct rate can be improved to 90% for the PCA-SVM algorithm with 21 principal components.
The non-invasive detection of blood glucose based on photoacoustic spectroscopy is a very popular method used to monitor the diabetes mellitus in recent years. The basic mechanism of photoacoustic spectroscopy is the effect of photo-induced ultrasonic. The detection accuracy of blood glucose can be improved due to the captured ultrasonic rather than the photons. The properties of ultrasonic transducer is one of the important influence factors on the detection accuracy of glucose. To study the effect of detection frequency for ultrasonic transducer on the glucose detection based on photoacoustic spectroscopy, a set of photoacoustic detection system was established. The optical parameters oscillator (OPO) pulsed laser pumped with 532nm was used as the excitation light source. Three kinds of ultrasonic transducers with different central echo frequencies (1MHz, 2.5MHz, and 30MHz) were respectively used to capture the photoacoustic signal of test blood phantoms with different concentrations of glucose. The time-resolved photoacoustic signal and peak-to-peak values of test blood phantoms were obtained. The results show that with the increase of glucose concentration, the photoacoustic amplitudes and peak-to-peak values of phantoms increase. Moreover, the time of photoacoustic signal shifts left with the increase of concentration. The prediction models based on linear fitting method were established for three kinds of ultrasonic transducers. Prediction results show that for the ultrasonic transducer with central frequency of 1MHz, the correction coefficient is 0.8681, the root-mean-square error (RMSE) of glucose concentration is about 13.3%. For the ultrasonic transducer with central frequency of 2.5MHz, the correction coefficient is 0.83127, the RMSE of glucose concentration is about 1.8149%. For the ultrasonic transducer with central frequency of 30MHz, the correction coefficient is 0.99598, the RMSE of glucose concentration is about 0.3808%. Therefore, the detection effect of the ultrasonic transducer with central frequency of 30MHz is best compared with the two others.
To achieve the identification of true and fake blood, the near infrared spectroscopy method was used in this work. The optical absorption spectra of blood samples with 120 groups of training samples and 30 groups of test samples were obtained via a Fourier transform NIR spectroscope. Since the similar spectra profiles and spectra overlap between the blood samples, the accurate identification of true blood and fake blood is difficult from the visual viewpoint. The wavelet neural network was used to train and test the blood samples. The correct rate of identifying true and fake blood is only 23.3%. To improve the correct rate, the particle swarm optimization (PSO) algorithm was used to optimize the weights, two learning rate factors, translation factor and scaling factor of WNN network. At the same time, the effects of the neuron number in the hidden layer, two learning rate factors, two acceleration factors, iteration times and training times on the correct rate and mean square error of identifying blood based on WNN-PSO algorithm were investigated. Under the optimal parameters, the correct rate of WNN-PSO algorithm is improved to 53.3%. Then, the principal component analysis (PCA) method was used to further improve the correct rate. The effect of different principal components on the correct rate of identifying blood based on PCA-WNN-PSO algorithm was also investigated. The results show that the correct rate can reach 96.7% for the identification of blood by using the NIR spectroscopy combined with PCA-WNN-PSO algorithm.
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