Data acquisition system for photoacoustic technique

Abstract

With medical technology advancing at a rapid rate, improving the portability and mobility of biomedical instruments adds an extra advantage. The end-user would also desire the instrument to be easily manageable and simple to learn. To address these issues, a portable, low-cost and compact data acquisition system has been developed in this thesis, to capture and store photoacoustic signals. Utilizing the photoacoustic effect, it is possible to differentiate between healthy and unhealthy tissues using the proposed DAQ system, by analysing the acquired photoacoustic signals. A basic data acquisition system consists of a signal conditioning circuit, an ADC and a data displaying/analysing instrument. However, additional blocks may be added according to the desired application. The proposed DAQ includes a pre amplifier to amplify the microvolt-PA signal, an ADC circuit to convert the analog PA signal into digital and finally a microcontroller to read, store, manipulate and transfer the data to the PC. Additional circuits to boost the trigger signal and to purify the microcontroller-generated clock for the ADC have also been designed. The proposed DAQ has been incorporated in a custom-built laser diode-based excitation system to acquire photoacoustic signals in a PA imaging experimentation setup, to excite a black rubber sample. It was observed that the signal acquired using the proposed DAQ replicates the signal acquired using the traditional signal capturing instrument i.e., DSO. The thesis discusses a detailed description of the proposed setup and its components, including the methodology used in developing the prototype circuits and PCBs for different functions and the results for the same, proving the functionality and accuracy of the proposed DAQ system.