Application of synthetic aperture focusing to short-lag spatial coherence

It has been demonstrated that short-lag spatial coherence (SLSC) ultrasound imaging can provide improved SNR and CNR compared to conventional B-mode images, especially in the presence of noise and clutter. Application of the van Cittert-Zernike theorem predicts that coherence between the ultrasound echoes received across an array is reduced significantly away from the transmit focal depth, leading to a limited axial depth of eld in SLSC images. Transmit focus throughout the eld of view can be achieved using synthetic aperture methods to combine multiple transmit events into a single nal image. We propose the application of these methods to create synthetically focused channel data to be used to create an SLSC image that will have an extended axial depth of eld comparable to B-mode images. Experimental results in a phantom and in vivo are presented and compared to both B-mode images and dynamic receive focused SLSC images, demonstrating improved SNR and CNR away from the transmit focus and an enlarged axial depth of eld.