P. Beard, T. Mills
Jun 15, 2001
Journal name not available for this finding
A photoacoustic imaging system has been evaluated by mapping the temporal distribution of photoacoustic signals generated in a tissue phantom. The phantom comprised an Intralipid scattering solution (μs'=1mm-1 and μa=0.01mm-1) containing two regions of enhanced absorption; a 1.5mm thick layer (μa=1mm-1) and a 75μm layer (μa=40mm-1). These were located 1cm beneath the surface of the Intralipid which was irradiated with 7ns Q switched laser pulses of fluence 0.05 J/cm2. A Fabry Perot polymer film ultrasound sensing interferometer was used for the detection of the photoacoustic signals. A 1D ultrasound array was simulated by illuminating the sensing interferometer with a large diameter laser beam and line scanning a photodiode across the reflected output beam. The detection sensitivity of the system was 3kPA over a 25MHz measurement bandwidth, the 3dB acoustic bandwidth was 17.5MHz, the sensitive azimuthal 'array' aperture and element size were 12mm and 0.8mm respectively. Greyscale images of the time-resolved photoacoustic signals enabled both absorbers to be clearly identified with an axial spatial resolution of less than 100micrometers . It is envisaged that this approach could form the basis of a practical photoacoustic tissue imaging system.