1. A method for implementing and monitoring a thermal ablation procedure comprising: conducting a thermal ablation procedure by directing high intensity focused ultrasound at an ultrasound focus having an elongated focus shape encompassing tissue to be ablated in a subject; for an image composed of voxels representing a region of the subject encompassing said ultrasound focus, setting, in a computer, a cuboid shape of each of said voxels, as adapted voxels, dependent on said focus shape; and in said computer, generating said image of said region of the subject by composing said image of said adapted voxels, and including a representation of said ultrasound focus, with said cuboid shape, in said image composed of said adapted voxels.