1. A method of identifying candidate inter-tissue boundary lines in an ultrasound image, comprising: using a data processing device to implement the following steps: accessing an input ultrasound image, said input ultrasound image including rows and columns of pixels; identifying candidate boundary lines by: (a) dividing said input ultrasound image into discrete, sequential depth positions, each discrete depth position being defined by a fixed number of rows of pixels; (b) defining a plurality of horizontal band regions, each horizontal band region corresponding to a separate one of said discrete depth positions and fully encompassing its corresponding depth position, each horizontal band region spanning a plurality of sequential depth positions; (c) progressing, one discrete depth position at a time, along said input ultrasound image, and at each, current, depth position executing the following steps: (i) defining a plurality of potential boundary lines within the current horizontal band region that corresponds to the current depth position, each of the defined potential boundary lines traversing a common point within the current horizontal band at a different angle relative to the horizontal; (ii) defining a candidate band region corresponding to each potential boundary line following the trajectory of its corresponding boundary line and encompassing its corresponding boundary line; (iii) determining an intensity value for each potential boundary line based at least in part on the intensity of pixels within its corresponding candidate boundary region; (iv) recording the potential boundary line of highest intensity value as the candidate line for the current depth position; (d) collecting the intensity values of candidate lines recorded at the different depth positions into an intensity-depth histogram; (e) identifying as said candidate inter-tissue boundary lines the candidate lines that substantially correspond to peaks in said intensity-depth histogram.