1. An ultrasound imaging system, comprising: a first transmit aperture and a second transmit aperture configured to transmit first and second unfocused circular wave front ultrasound signals into a region of interest; a first receive aperture configured to receive echoes of the first and second unfocused circular wave front ultrasound signals; a controller configured to form a first image layer from received echoes of the first unfocused circular wave front ultrasound signal, and configured to form a second image layer from received echoes of the second unfocused circular wave front ultrasound signal; the controller being further configured to determine a value of a weighting factor by: determining a first distance from one of the first or second transmit apertures to a point represented by at least one pixel; determining a second distance from the point to the first receive aperture; summing the first distance and the second distance to obtain a total path length; and determining the weighting factor as a mathematical function of the total path length; the controller being further configured to apply the weighting factor to the at least one pixel of the first image layer to obtain a modified first image layer, and to combine the modified first image layer with the second image layer to form a combined image; and a display device configured to display the combined image.