Performance Issues in Glucose Concentration Measurements Using Photoacoustics

• Main Authors: Chien-Ming Cheng, 程健銘
• Other Authors: Pai-Chi Li
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/01874378508701405452

碩士 === 國立臺灣大學 === 電機工程學研究所 === 96 === In this research, glucose concentration measurements based on photoacoustic(PA) signal amplitude and acoustic velocity are studied. Determination of blood glucose level is a required procedure in diabetes care. Currently, the most common method involves collecting blood samples for chemical analysis, but it is invasive and prone to result in pain and skin injury. It is the purpose of this study to investigate the feasibility of non-invasive glucose measurements based on PA and ultrasonic measurements. The PA setup includes a source Ti:sapphire laser and a line-focused single-crystal ultrasound transducer operating at 1 MHz. The transducer was arranged perpendicular to the incident laser beam for sideward detection. Our experiment results reveal that the PA amplitude increases by about 2% when the glucose concentration increases by 1%, and the standard deviation is around 1.5% to 2%. The standard deviation results from thermal noise, which can be decreased by signal averaging and the instable laser output. On the other hand, sound velocity was estimated by pulse echo measurements. The experimental setup included an ultrasound transducer operating at 20 MHz, with the distance between the ultrasound transducer and a reflector being 1 cm. The experiment results show that the time of flight decreases by 0.18% when the glucose concentration increases by 1% and the standard deviation is around 0.2ns, which is mainly caused by jitter. In conclusion, our measurements show that a 1% concentration change is detectable. However, the FDA requires a 0.01% detectability. We have also performed preliminary experiments with hemoglobin solution. Results show that the PA amplitude increases by about 1.4% and the time of flight decreases by about 0.18% when the glucose concentration increases by 1%. Future works will focus on improving the method by using multiple-laser wavelength, and to study influence of blood constituents.