A Camera-based Fluorescence-dependent Temperature Sensor for Neonatal Care

There are many examples of wireless non-contact temperature measurement systems out there but most of them are work at high temperatures or do not have sufficient resolution for use in the physiological domain (30�C-42�C). Even to this date, temperature measurement in incubators is done by attaching thermistor probes to the skin of the baby. This thesis presents a non-contact temperature measurement system designed for neonatal care. The system removes the need of attaching thermistor probes to the neonate's skin and therefore reduces the risk of epidermal stripping, microbial infections, etc. The fluorescence intensity ratio (ratiometric) technique is utilized to determine the temperature of a target using temperature responsive fluorophores. This technique measures the changes in the fluorescence intensity as the temperature is changed. The ratiometric technique utilizes two separate fluorophores where one is non-sensitive to temperature and thus serves as a reference. Determining results using ratiometric techniques also minimizes changes in the final measurements when environmental changes such as changes in ambient lights occur. An illuminator is employed to excite the fluorophores which then emit fluorescence that is measured by a camera. This is done by capturing consecutive frames with the illuminator on and then off and then subtracting them. The data is captured, stored, pre-processed and sent to the computer using an FPGA. The MATLAB computational environment is utilized to carry out final processing and display of the ratiometric values. The thesis looks into variable situational changes that can present themselves during actual application of the system and studies the effect on the stability of the ratiometric fluorescence measured. Measurements of the ratiometric fluorescence under different conditions suggest that a low-cost sensing system is viable. The resolution of the system is reported to be better than 0.18˚C