FAST MAPPING OF VOLUMETRIC DENSITY DATA ONTO A TWO-DIMENSIONAL SCREEN

A method and system for constructing from volumetric CT or MRI scan data of a patient region, a virtual two-dimensional fluoroscopic image of the patient region as seen from a selected point in space are disclosed. In practicing the method, a plurality of rays are constructed between a selected view point and each of a plurality of points in an XY array, where at least some of the rays pass through the patient target region, the points in the XY array correspond to the XY array of pixels in a display screen, and each pixel in the display screen includes multiple N-bit registers for receiving digital-scale values for each of multiple colors. For each pixel element, a sum of all M-bit density values associated with voxels along a ray extending from the selected point to the associated pixel element is calculated. The summing is carried out by distributing the M bits in the voxel density values among the multiple N-bit registers of that pixel, such that such that one or more bit positions of each M-bit value is assigned to a selected register. The image constructed of gray-scale values representing the summed M-bit density values at each pixel in the screen is displayed to the user.