23 March 2017 Acoustic resolution photoacoustic Doppler flowmetry using a transducer array: optimising processing for velocity contrast
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Abstract
This work demonstrates the first measurements of blood flow velocity using photoacoustic flowmetry (PAF) employing a transducer array. The measurements were made in a flow phantom consisting of a tube (580 μm inner diameter) containing blood flowing steadily at physiological speeds ranging from 3 mm/s to 25 mm/s. Velocity measurements were based on the generation of two successive photoacoustic (PA) signals using two laser pulses with a wavelength of 1064 nm; the PA signals were detected using a 64-element transducer array with a -6 dB detection bandwidth of 11-17 MHz. We developed a processing pipeline to optimise a cross-correlation based velocity measurement method comprising the following processing steps: image reconstruction, filtering, displacement detection, and masking. We found no difference in flow detection accuracy when choosing different image reconstruction algorithms (time reversal, Fourier transformation, and delay-and-sum). High-pass filtering and wallfiltering were however found to be essential pre-processing steps in order to recover the correct displacement information. We masked the calculated velocity map based on the amplitude of the cross-correlation function in order to define the region of interest corresponding to highest signal amplitude. These developments enabled blood flow measurements using a transducer array, bringing PAF one step closer to clinical applicability.
Conference Presentation
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T. M. Bücking, P. J. van den Berg, S. Balabani, W. Steenbergen, P. C. Beard, J. Brunker, "Acoustic resolution photoacoustic Doppler flowmetry using a transducer array: optimising processing for velocity contrast", Proc. SPIE 10064, Photons Plus Ultrasound: Imaging and Sensing 2017, 100642M (23 March 2017); doi: 10.1117/12.2252939; https://doi.org/10.1117/12.2252939
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