MC-GPU is a Monte Carlo simulation code that can generate synthetic radio-graphic images and computed tomography (CT) scans of realistic models of the humananatomy using the computational power of commodity Graphics Processing Unit (GPU)cards. The code implements a massively multi-threaded Monte Carlo simulation algo-rithm for the transport of x rays in a voxelized geometry. The x ray interaction modelsand material properties have been adapted from PENELOPE 2006 ...