General purpose graphics processing unit speedup of integral relative electron density calculation for proton computed tomography

Currently proton dose calculations rely on X-ray computed tomography (CT), which limits their accuracy due to the physical interaction differences of protons and X-rays. To gain the maximum benefit from proton therapy, proton computed tomography (pCT) offers the opportunity to more accurately plan proton doses and to verify the correct proton beam delivery in the treatment position. A vital step in the reconstruction of a pCT image is the calculation of the integral relative electron densities, which must be known for each of the proton histories. This paper will focus on the hardware acceleration of the integral relative electron density calculation. The integral relative electron density requires the incoming and outgoing energies of the protons being tracked, which is given by the detectors.