Proton computed tomography (pCT) is an imaging modality beingdeveloped to support targeted dose delivery in proton therapy. It aimsto accurately map the distribution of relative stopping power in theimaged body. Because protons traverse material in non-linear paths,pCT requires individual proton processing and image reconstructionbecomes a time-consuming process. We discuss the transformation ofimage reconstruction techniques from single CPU/GPU implementations tocreate a hybrid multi-CPU/GPU approach. We demonstrate a reduction ofcomputation time from almost 7 hours down to 53 seconds.