Photoacoustic and thermoacoustic imaging for biomedical applications

Abstract

Based on the measurement of ultrasonic waves induced by electromagnetic pulses, photoacoustic imaging and thermoacoustic imaging can reveal optical or dielectric properties of tissues that are closely related to the physiological and pathological status of tissues and they have became the promising clinical imaging modalities. In this paper, a high frame rate tomography instrument with 64-channel parallel data-acquisition system was designed and developed for photoacoustic biomedical imaging. In the system, the pulse-laser-induced ultrasonic signals are converted to voltage signals by a 128-element linear ultrasound transducer array. The 128-channel signals are acquired by the 64-channel parallel data-acquisition system twice through the 2:1 multiplexer, and the OPO (optical parametric oscillator) laser provides laser with a pulse repetition rate of 15 Hz. Therefore, the acquisition rate can reach about 7 frames per second and photoacoustic images can be displayed dynamically. Based on the above signal acquisition system, biomedical application of photoacoustic imaging was explored and successfully performed. Fast photoacoustic tomography for flow-field visualization was demonstrated by flowing object. Thermoacoustic tomography was developed to detection of low-density foreign targets in small animals which was indistinguishable with X-ray. All the experimental results show that photoacoustic and thermoacoustic imaging with fast parallel data-acquisition system is a highly-efficient approach for functional imaging of biomedical tissues.