Generalized contrast-to-noise ratio as a metric of photoacoustic image quality
Multiple image quality metrics are currently available to assess target detectability in photoacoustic images. Common metrics include contrast, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). The generalized contrast-to-noise ratio (gCNR) is a relatively new image quality metric to assess the probability of photoacoustic target detectability. This paper demonstrates the applicability of gCNR to assess photoacoustic image quality using simulated and experimental images created with delay-and-sum (DAS), short-lag spatial coherence (SLSC), generalized coherence factor weighting combined with DAS (GCF+DAS), and minimum variance (MV) beamforming. Images were created from data acquired with a fixed light source with output energy values increasing from 2 mJ to 35 mJ. The gCNR converged to 0.93, 0.98, 0.99, and 0.85 for DAS, SLSC, GCF+DAS, and MV beamforming, respectively, at energies of approximately 20, 10, 10, and 20 mJ, respectively. These results indicate that gCNR has the potential to determine the minimum laser energy needed to maximize the detectability of a photoacoustic target for any given image formation method.