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As an emerging medical diagnostic technology, photoacoustic imaging has been implemented for both preclinical and clinical applications. For clinical convenience, a handheld free-scan photoacoustic tomography (PAT) system providing 3D imaging capability is essentially needed, which has potential for surgical navigation and disease diagnosis. In this paper, we proposed a free-scan 3D PAT (fsPAT) system based on a handheld linear-array ultrasound probe. A global positioning system (GPS) is applied for ultrasound probe's coordinate acquisition. The proposed fsPAT can simultaneously realize real-time 2D imaging and large field-of-view 3D volumetric imaging, which is reconstructed from the multiple 2D images with coordinate information acquired by the GPS. To form a high-quality 3D image, a dedicated space transformation method and a reconstruction algorithm are used and validated by the proposed system. Both simulation and experimental studies have been performed to prove the feasibility of the proposed fsPAT. To explore its clinical potential, in vivo 3D imaging of human wrist vessels is also conducted, showing a clear subcutaneous vessel network with high image contrast. [ABSTRACT FROM AUTHOR]

Photoacoustic tomography (PAT) is an emerging technology for biomedical imaging that combines the superiorities of high optical contrast and acoustic penetration. In the PAT system, more PA signals are preferred to be detected from full field of view to reconstruct the PA images with higher fidelity. However, the requirement for more PA signals’ detection leads to more time consumption for single-channel scanning-based PAT system or higher cost of data acquisition (DAQ) module for an array-based PAT system. To address this issue, we proposed a programmable acoustic delay-line (PADL) module to reduce DAQ cost and accelerate imaging speed for PAT system. The module is based on bidirectional conversion between acoustic signals and electrical signals, including ultrasound transmission in between to provide sufficient time delay. The acoustic delay-line module achieves tens or hundreds of microseconds’ delay for each channel and is controlled by a programmable control unit. In this work, it achieves to merge four inputs of PA signals into one output signal, which can be recovered into original four PA signals in the digital domain after DAQ. The imaging experiments of pencil leads embedded in agar phantom are conducted by the PAT system equipped with the proposed PADL module, which demonstrated its feasibility to reduce the cost of the PAT system. An in vivo study of human finger PAT imaging with delay-line module verified its feasibility for biomedical imaging applications. [ABSTRACT FROM AUTHOR]

Photoacoustic imaging has undergone rapid development in recent years. To simulate photoacoustic imaging on a computer, the most popular MATLAB toolbox currently used for the forward projection process is k-Wave. However, k-Wave suffers from significant computation time. Here we propose a straightforward simulation approach based on superposed Wave (s-Wave) to accelerate photoacoustic simulation. In this study, we consider the initial pressure distribution as a collection of individual pixels. By obtaining standard sensor data from a single pixel beforehand, we can easily manipulate the phase and amplitude of the sensor data for specific pixels using loop and multiplication operators. The effectiveness of this approach is validated through an optimization-based reconstruction algorithm. The results reveal significantly reduced computation time compared with k-Wave. Particularly in a sparse 3-D configuration, s-Wave exhibits a speed improvement >2000 times compared with k-Wave. In terms of optimization-based image reconstruction, in vivo imaging results reveal that using the s-Wave method yields images highly similar to those obtained using k-Wave, while reducing the reconstruction time by approximately 50 times. Proposed here is an accelerated optimization-based algorithm for photoacoustic image reconstruction, using the fast s-Wave forward projection simulation. Our method achieves substantial time savings, particularly in sparse system configurations. Future work will focus on further optimizing the algorithm and expanding its applicability to a broader range of photoacoustic imaging scenarios. [ABSTRACT FROM AUTHOR]

The phasor field technique has been demonstrated as a powerful tool to improve imaging performance and reduce computational complexity in time of flight imaging. In this work, we show a similar description and propose phasor field photoacoustics (PAs), a framework for forward acoustic propagation and backward source reconstruction, using phasor representations of acoustic pressure and back projection events. Based on the linear propagation mechanism, this method employs complex phasor filters to decompose the photoacoustic wave into pairs of orthogonal virtual waves, wherein each pair of orthogonal waves corresponds to the real and imaginary parts of the quasi-monochromatic phasor field contribution. By performing phasor field projection (PFP) and thereafter conjugated multiplication in the spatial domain, the complex envelope containing local amplitude and phase information can be faithfully retrieved, attaining rigorous "unipolar" photoacoustic images without ambiguous negative absorption artifacts. Theoretical and experimental results demonstrate that the orthogonal virtual wave based phasor field photoacoustic method can effectively eliminate negative artifacts and improve imaging signal-to-noise ratio (SNR) without excessively increasing computational complexity. This work may pave the way for high-fidelity quantitative imaging, e.g., multispectral and molecular imaging applications. [ABSTRACT FROM AUTHOR]