Glucose Concentration Measurements Utilizing a Photoacoustic Technique
Date Issued
2006
Date
2006
Author(s)
Hsu, Chih-Wei
DOI
zh-TW
Abstract
Feasibility of glucose concentration measurements utilizing photoacoustic (PA) approach is explored in this research. Estimating glucose concentration by means of PA measurements has the advantages of non-invasiveness and concentration level evaluation based on both optical and acoustic characteristics of glucose molecules. Most current measurements methods make use of the dependence of blood glucose molecules absorption in NIR range. However, the variation of the absorption within human body is merely 0.2%, which in turn causes measurement in optical manner vulnerable to scattering, an important phenomenon in skin tissues. Photoacoustic signal is induced through thermal expansion of the locally heated area by incident laser pulse. By means of PA measurements, not only scattering interference can be reduced, but also the acoustic parameters, such as sound velocity, are able to be used to enhance the accuracy. In this thesis, glucose concentration measurements via PA signal amplitude and acoustic velocity variations are combined. Experiments are set up with a Ti:sapphire laser, a single-crystal ultrasound transducer, and a 100MHz ADC card. The PA signals from the glucose solution are received sidewardly and forwardly. Transducers operating at 1MHz but at different focus depths are used for different receiving modes, where a 1.8cm focal depth, point-focusing transducer is aligned along the laser beam as the forward receiving mode, and a focal depth of 1.27cm, line-focusing one is arranged perpendicularly with the direction of the incident beam for the sideward receiving one. Two glucose-concentration measurement approaches are carried out, including variation evaluation of the PA signal amplitude and sound velocity. Our experiment results reveal that a 0.3% concentration variation is detectable. The error is mostly due to the instability of laser output energy and asynchronization between laser, photodiode detector, and ADC. Future work includes detection in plasma both in vitro and in vivo, improvement in system sensitivity, further understanding of light scattering by red blood cell and discrimination of other molecules in blood utilizing PA absorption spectra.
Subjects
光聲效應
非侵入式
葡萄糖濃度
聲速
近紅外光
血糖
photoacoustic
noninvasive
glucose concentration
sound velocity
near infrared
blood glucose
Type
thesis
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