Photoacoustic clutter reduction using short-lag spatial coherence weighted imaging

Photoacoustic imaging suffers from various sources of clutter to a greater extent than conventional ultrasound imaging. As a result, rather than a limited detector sensitivity or low fluence at depth, clutter is the main limitation in the maximum achievable image depth. In this work a method is presented that exploits the difference in spatial coherence across the transducer surface, expressed by the short-lag spatial coherence metric, to distinguish between signal and clutter. Using this metric as a weighting factor on a photoacoustic image, clutter is strongly suppressed while the photoacoustic amplitude is largely preserved. Using a clinical photoacoustic scanner, images were obtained of both a phantom and the first author´s inner elbow, and strong clutter reduction was observed in both cases. Using the presented method, the effective imaging depth was doubled, both in phantoms and in vivo, without altering the fluence or the acquisition scheme.