Photoacoustic (PA) imaging technology integrates the deep penetration depth of ultrasound imaging with the high resolution of optical imaging, demonstrating significant potential in biomedical applications. Many preclinical studies and clinical applications urgently require a portable, high-quality, low-cost, and fast imaging system. Thus, translating advanced image reconstruction algorithms into hardware implementations is highly desired. However, existing iterative PA image reconstructions, although exhibit higher accuracy than the delay-and-sum algorithm, suffer from high computational cost. In this paper, we introduce a novel model-based hardware architecture for palm-size PA tomography (palm-PAT), aiming at enhancing both the speed and performance of image reconstruction at a much lower system cost. To achieve this, we propose an innovative data reuse method that significantly reduces the consumption of hardware storage resources, achieving a reduction of approximately 75% in hardware storage requirements. We conducted experiments utilizing the FPGA implementation of the algorithm, using phantom, human finger data in vivo and ex vivo breast tumor data to verify the feasibility of the proposed method. The results demonstrate that our proposed architecture can substantially reduce system cost while maintaining high imaging performance. The novel hardware architecture design of the model-based algorithm achieves a speedup of up to approximately 270 times compared to the CPU, while the corresponding energy efficiency ratio is improved by more than 2700 times.

Photoacoustic tomography (PAT) is an emerging biomedical imaging technology. Many kinds of PAT imaging modalities are applied in various biomedical applications. However, for the conventional PAT system setup, the ringdistribution ultrasonic transducer (UT) array only receives PA signals from fixed region of interest (ROI) that limit the flexibility for imaging objects with different sizes. In this paper, a size-adjustable PAT system with sectorial ultrasonic transducer array (SUTA) is proposed. Four 70.8-degree 32- elements SUTAs with different center frequency are placed around the target to receive 128 channels' PA signals. The four SUTAs can adjust the imaging ROI's radius ranging from 50 mm to 90 mm, which greatly improves the size-adjustable capability of PAT system. The four SUTAs received signals are used to recover the original PA signals based on physical model accordingly. To prove the concept, the feasibility of the size- adjustable PAT imaging is firstly verified by the simulation results using MATLAB k-wave toolbox. Moreover, a 3-D printed vascular phantom is imaged by the proposed PAT system validating its feasibility very well.

Photoacoustic tomography (PAT) is a newcomer in the biomedical imaging community. The image is constructed through photoacoustic waves emitted from the sample after absorbing light energy. The ultrasound signals are converted into electrical signals by ultrasound transducers and sent to a multi-channel data acquisition (DAQ) system for transmission to the personal computer. Traditionally, one ultrasound signal would occupy one channel of the DAQ. However, high-performance DAQ is awfully expensive. Nowadays, to improve PAT's imaging result, imaging systems with multi-detector is usually required, which means multi-channel DAQ is exceedingly desired. Therefore, in this paper, a 4-to-1 circuit module is proposed to reduce the PAT system's cost by fusing four channels of signals into one signal employing frequency- division multiplexing (FDM). Specifically, the original four PA signals are multiplied with high-frequency sine waves with different frequencies and then summed into one channel so that the signals are carried separately in a bandwidth that does not overlap in the frequency domain. After the modulated signal's acquisition, the original signal can be recovered through bandpass filters and an associated demodulation algorithm. We have performed imaging experiments and proved the feasibility of this module in the PAT system.

Photoacoustic imaging has attracted increasing research interest in recent years due to its unique merit of combining light and sound. Enabling deep tissue imaging with high ultrasound spatial resolution and optical absorption contrast, photoacoustic imaging has been applied in various application scenarios including anatomical, functional and molecular imaging. However, the bulky and expensive laser source is one of the key bottlenecks that need to address for further compact system development. Photoacoustic imaging system based on low-cost laser diode (LD) is one of the promising solutions. In this paper, we report a custom-made fingertip laser diode system enabling both pulsed and continuous modulation modes with shortest pulse-width of 40 ns, largest driving current of 13 A, and highest modulation frequency of 3 MHz, which are suitable for both time and frequency domain photoacoustic imaging. To the best of our knowledge, this may be the most compact laser source reported for photoacoustic imaging. Owing to its super-compact size, the proposed LD system could pave the pathway to low-cost photoacoustic sensing and imaging device, even wearable photoacoustic biomedical sensors.