1. A method for determining speed-of-sound factors in ultrasound images of a body, comprising: capturing at least two ultrasound images of an internal body region from different directions; registering the at least two ultrasound images with respect to a corresponding region in a body reference model; comparing the registrations of each of the at least two ultrasound images with a registration of at least one other ultrasound image captured from a different direction, or with another reference registration; and determining the speed-of-sound factor for each individual ultrasound direction from the comparison of reference model point distances for a particular registered structure.