A Comparison of Image Reconstruction Methods for Ring-Array Photoacoustic Computed Tomography.

This work compares the effectiveness of four image reconstruction techniques for a ring-array photoacoustic computed tomography (PACT) system: the delay-and-sum (DAS), the interpolated model matrix inversion (IMMI), the frequency-domain model-based (FDMB), and the time-reversal (TR) methods. Image quality, computational efficiency, and robustness to noise and spatial/electrical impulse response (EIR) are evaluated to assess the four methods for 2-D imaging. Although it is thought to have limitations in producing high-resolution and artifact-free images, the DAS method is commonly employed in clinical applications because of its simplicity and real-time imaging capability. On the other hand, model-based (MB) methods, such as the IMMI, the FDMB, and the TR methods, use comprehensive physics for a more accurate description of wave propagation through tissue and thus have the potential to provide higher image quality and quantitative information. These approaches, however, require substantially more processing power, which can make them less suitable for real-time applications. Our results show that the DAS method achieves real-time performance while delivering better image quality for an ex vivo elongated target, whereas both the IMMI and the FDMB methods provide enhanced detail and resolution for thin-slice targets, at the cost of considerably slower reconstruction times. The TR method achieves reasonable resolution and detail for all cases but shows the slowest image reconstruction time. This work highlights the strengths and limitations of each method, offering valuable insights into selecting the most appropriate reconstruction technique for ring-array PACT systems.