FIP Special Seminar - Postdoc Speaker Award "Switchable multiscale photoacoustic microscopy"
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Wed, 03/21/2018 - 12:00 to 13:00
Dr. Wei Liu, Postdoctoral Research, Biomedical Engineering, Duke University
We report a switchable multiscale photoacoustic microscopy combined with ultrasound as a useful tool for high-resolution and deep-penetration tomography imaging. The focused transducer has dual elements with two individual central frequencies 20 MHz and 40MHz, resulting in different acoustic resolutions and penetration depths. The lateral resolutions of the microscopy for the ultrasonic imaging are inherent, which are acoustically determined by the transducer's frequency and measured as 222 µm for the high-frequency element and 360 µm for the low-frequency one at the acoustic focus plane. The spot size of the excitation beam was adjusted as much smaller than the true acoustically-determined resolutions, resulting in that the lateral resolution of photoacoustic imaging is dependent on the beam size. The photoacoustic lateral resolution is switchable by putting a flip-mounted beam-shaping lens on the optical pathway; it was measured as 6.9 µm when the switchable lens was off and the system was then degraded as a typical optical-resolution photoacoustic microscopy, otherwise the system was an acoustic-resolution photoacoustic microscopy with a lateral resolution of 76.3 µm. The axial resolution for both photoacoustic and ultrasonic imaging are determined by the bandwidth of the transducer, which was measured as 42 µm. The combination of photoacoustics and ultrasound emerges the advantages of photoacoustics in its superior sensitivity to optical absorption contrast...