1. A method for use in ultrasound imaging of matter in a region, the method comprising: providing wave energy into the region, the wave energy having a pulse spectrum centered at a fundamental frequency; transducing wave energy returned from the region to form a set of receive signals; beamforming the set of receive signals to provide beamformed data representative of at least a portion of the region; separating the linear and non-linear components of the beamformed data based on a pth-order Volterra model, where p is equal to or greater than 2, wherein separating the linear and non-linear components of the beamformed data based on a pth-order Volterra model comprises applying at least one non-linear filter kernel of one or more non-linear filter kernels of a pth-order Volterra filter to the beamformed data, wherein applying the at least one non-linear filter kernel comprises defining coefficients for the at least one non-linear filter kernel using at least a two-dimensional autocorrelation; and processing at least the non-linear components of the beamformed data for use in forming an image.