Generalized spatial coherence reconstruction for photoacoustic computed tomography

Abstract

Significance: Coherence, a fundamental property of waves and fields, plays a key role in photoacoustic image reconstruction. Previously, techniques such as short-lag spatial coherence (SLSC) and filtered delay, multiply, and sum (FDMAS) have utilized spatial coherence to improve the reconstructed resolution and contrast with respect to delay-and-sum (DAS). While SLSC uses spatial coherence directly as the imaging contrast, FDMAS employs spatial coherence implicitly. Despite being more robust against noise, both techniques have their own drawbacks: SLSC does not preserve a relative signal magnitude, and FDMAS shows a reduced contrast-to-noise ratio.Aim: To overcome these limitations, our aim is to develop a beamforming algorithmgeneralized spatial coherence (GSC)-that unifies SLSC and FDMAS into a single equation and outperforms both beamformers.Approach: We demonstrated the application of GSC in photoacoustic computed tomography (PACT) through simulation and experiments and compared it to previous beamformers: DAS, FDMAS, and SLSC.Results: GSC outperforms the imaging metrics of previous state-of-the-art coherence-based beamformers in both simulation and experiments.Conclusions: GSC is an innovative reconstruction algorithm for PACT, which combines the strengths of FDMAS and SLSC expanding PACT's applications.

Development of a thermoacoustic imaging system to image blood in the brain: preliminary ex-vivo results

“…Subsequently, we introduced several filtering steps to further improve signal quality, incorporating bandpass filtering on the raw TA signals within a frequency range of 0.5-4MHz to retain pertinent frequency components while suppressing noise and interference. For image reconstruction, we implemented a short-lag spatial coherence (SLSC) reconstruction algorithm optimized for TA signals, which reconstructs images by determining the cross-correlation among the 64 detector elements of the US transducer, analyzing results from different element separations or lags [40].…”