12 February 2009 Photoacoustic imaging with limited diffraction beam transducers
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Abstract
Photoacoustic imaging with a scanning, fixed focus receiver gives images with high resolution, without the need for reconstruction algorithms. However, the usually employed spherical ultrasound lenses have a limited focal depth that decreases with increasing lateral resolution due to the inverse relation between numerical aperture and Rayleigh length. In this study the use of an axicon detector is proposed, consisting of a conical surface onto which a piezoelectric polymer film is attached. The detector is characterized in simulations and in experiments, demonstrating the expected high resolution over an extended depth of focus. Simulated and experimental images reveal X-shaped artifacts that are due to the conical detector surface. Since the point spread function (PSF) of the detector is spatially invariant over the depth of field, a frequency domain deconvolution can be applied to the images. Although this clearly improves the image quality in simulations, the reduction of artifacts was not so efficient in experiments. However, the detector is able to produce images with accurate position and shape of objects. Moreover, the axicon transducer rejects signals from planar surfaces (e.g. the skin surface) and favors signals from small, isolated sources.
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Günther Paltauf, Sibylle Gratt, Klaus Passler, Robert Nuster, Peter Burgholzer, "Photoacoustic imaging with limited diffraction beam transducers", Proc. SPIE 7177, Photons Plus Ultrasound: Imaging and Sensing 2009, 71770S (12 February 2009); doi: 10.1117/12.808217; https://doi.org/10.1117/12.808217
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