A photoacoustics based continuous non-invasive blood glucose monitoring system

Abstract

The paper examines the use of photoacoustic spectroscopy (PAS) for making continuous non-invasive blood glucose measurements. An apparatus for performing photoacoustic (PA) measurements is constructed and the technique is verified in vitro and in vivo through measurements on glucose solutions and live tissue. The signal amplitude is observed to increase with the glucose concentration in both cases. A linear calibration method is applied on each individual to obtain a glucose concentration value from each PA measurement. The glucose values obtained are compared with reference glucose concentrations measured using a standard glucose meter, giving a mean absolute difference (MAD) of 23.75 mg/dl and a mean absolute relative difference (MARD) of 18.03%. A plot of 196 measurement pairs taken over 30 normal subjects on a Clarke Error Grid gives a point distribution of 67.86%, 31.12%, 0.0%, 1.02% and 0.0% over zones A to E of the grid. This performance is an improvement over those obtained previously using PAS and point to the potential of the technique for non-invasive glucose measurements. An FPGA based reconfigurable embedded architecture is proposed for high speed data acquisition, noise reduction and display of PA measurements. The architecture operates at 274.823 MHz on a Xilinx Virtex-II Pro FPGA providing an SNR improvement of 30 dB and enabling a portable blood glucose monitoring system.