We propose a GPU-accelerated implementation of frequency-domain synthetic aperture focusing technique (SAFT) employing truncated regularized inverse k-space interpolation. Our implementation achieves sub-1s reconstruction time for data sizes of up to 100 M voxels, providing more than a tenfold decrease in reconstruction time as compared to CPU-based SAFT. We provide an empirical model that can be used to predict the execution time of quasi-3D reconstruction for any data size given the specifications of the computing system.
Spherical ultrasonic antennas are used in raster-scan optoacoustic (OA) angiography to record broadband signals generated by haemoglobin molecules in blood when they absorb pulsed optical radiation. Depending on the size of haemoglobin-containing structures, the characteristic frequencies of OA signals can vary quite significantly, ranging from hundreds of kilohertz to hundreds of megahertz. Meanwhile, the bandwidth of the receiving frequency band of standard piezoelectric sensors, as a rule, does not exceed the centre frequency value. It is possible to expand the receiving band of ultrasonic detectors to the required 0.1 kHz – 100 MHz values by using nonresonant piezomaterials based on polyvinidylene fluoride (PVDF). Two ultra-wideband detectors based on PVDF piezofilms of different thicknesses (9 μm and 25 μm) with different amplitude-frequency characteristics are experimentally compared. Comparative OA imaging of a tissue-like phantom demonstrates that the low-frequency sensor (film thickness l = 25 μm) has a greater depth of field, while the high-frequency sensor (l = 9 μm) has a better sensitivity in the range of 40 – 100 MHz. Using OA imaging of an experimental tumour in vivo, it is shown that a sensor with l = 25 μm is better suited for examining normal tissue containing relatively large blood vessels, while a sensor with l = 9 μm is better suited for studying tumour tissue containing a large number of multidirectional blood vessels of minimal size comparable to the maximum spatial resolution of the OA system.
A dual-wavelength 532/1064 nm optoacoustic (OA) imaging system allows 3D visualizations of arteriovenous anastomoses (AVAs) with an acoustic spatial resolution (50 µm) at depths of up to 2 mm in vivo in rabbit ears. Both structural and spectral information from the OA data are employed to analyze the anatomical locations of the blood vessels and to distinguish between veins and arteries in the zone of their confluence. The OA monitoring of a rabbit ear under temperature-induced (43 °C/15 °C) shunting demonstrated the potential of the technique for the monitoring of functional arteriovenous anastomosis.
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