1. A non-transitory program storage device readable by a machine, the device tangibly embodying a program of instructions executable by the machine for imaging a three-dimensional (3D) volume defined by a data set of voxels, the instructions being executable to implement: creating a three-dimensional (3D) sampling probe, wherein the 3D sampling probe is a sub-volume of the 3D volume; processing only the data set of voxels that intersect the 3D sampling probe; drawing only an image of at least a portion of one of the 3D sampling probe and the 3D volume, the image comprising an intersection of the 3D sampling probe and the 3D volume; and repeating the drawing step responsive to movement of the 3D sampling probe within the 3D volume so that as the 3D sampling probe moves through the 3D volume, the image of the 3D sampling probe is redrawn sufficiently fast to be perceived in real-time as the 3D sampling probe is moved