In non-invasive blood sensing with near-infrared (NIR) reflectance spectroscopy, optical probe usually directly contacts skin to eliminate specular reflection. Due to the direct contact, changes in contact pressure can lead to changes in internal structure and components distribution of the measured site, and thus introduces great interference into the final results. In this paper, we use self-made AOTF spectrophotometer to investigate the changes of reflectance spectrum with changing contact status for tissues in vitro (fresh porcine skin) and in vivo (two volunteers' left palms) at wavelengths ranging from 1100 nm to 1700 nm. The results show that with increasing degree of contact, energy of reflectance spectrum gradually decreases and the trend goes stable with time. However, the decreasing degree is related to wavelengths, which potentially suggests an indirect relevance with changes of components in tissues. Meanwhile, the results provide a practical solution to determining the optimum contact status between probe and skin.
Utilizing Near-infrared Spectroscopy for non-invasive glucose concentration sensing has been a focusing topic in biomedical optics applications. In this paper study on measuring conditions of spectroscopy on human body is carried out and a series of experiments on glucose concentration sensing are conducted. First, Monte Carlo method is applied to simulate and calculate photons’ penetration depth within skin tissues at 1600 nm. The simulation results indicate that applying our designed optical probe, the detected photons can penetrate epidermis of the palm and meet the glucose sensing requirements within the dermis. Second, we analyze the influence of the measured position variations and the contact pressure between the optical fiber probe and the measured position on the measured spectrum during spectroscopic measurement of a human body. And, a measurement conditions reproduction system is introduced to enhance the measurement repeatability. Furthermore, through a series of transmittance experiments on glucose aqueous solutions sensing from simple to complex we found that though some absorption variation information of glucose can be obtained from measurements using NIR spectroscopy, while under the same measuring conditions and with the same modeling method, choices toward measured components reduce when complication degree of components increases, and this causes a decreased prediction accuracy. Finally, OGTT experiments were performed, and a PLS (Partial Least Square) mathematical model for a single experiment was built. We can easily get a prediction expressed as RMSEP (Root Mean Square Error of Prediction) with a value of 0.5-0.8mmol/dl. But the model’s extended application and reliability need more investigation.
Non-invasive blood glucose sensing often employs contact measurement, that is, the optical probe directly contacts the skin to reduce specular reflection. The contact pressure and the variation of skin temperature therefore contribute much to interference incurred by the internal structure and composition change of the detecting part. In this paper, we are going to discuss the influence of contact pressure between fiberoptic probe and skin as well as heat transfer on spectral measurement. A through investigation is made on approaches to eliminate these factors for both contact and non-contact measurement.
Videokymography (VKG) is a powerful and cost-friendly method to observe the variability of the vocal fold vibration. A new quantitative method based on image processing, which introduces snakes model and genetic algorithm to improve precision and speed, is presented to analyze the vibration information in VKG automatically. To verify the precision of the proposed algorithm, an indirect simulation setup of vocal folds has been performed. One hundred and twenty images from twelve subjects have been analyzed, and the result shows that the vibration characteristics of vocal folds can be recognized more exactly, and the diseases in vocal fold can be diagnosed quantitatively.