Study of proton computed tomography using GEANT4 simulation

Feasibility of a proton computed tomography has been studied using a GEANT4-based simulation. The geometry contains an elliptic water phantom and a plane detector. The water phantom comprises two disks for artificial organs which represent a dense bone and a inflated lung, respectively. The diameter of the water phantom was 300 mm in long side and 260 mm in short side. The diameters of artificial organs were equally 30 mm. The water phantom was scanned with 250 MeV mono energetic protons by rotating the water phantom from 0 degree to 360 degree in 1 degree increments. The simulated results were analyzed as the projected profiles from the energy losses of protons and the initial beam positions where the residual energy was obtained from the plane detector. The image was then reconstructed with the simple back projection method. The both artificial organs were distinguishable in the reconstructed image by using penetrating tracks of which lateral displacements are less than 1 mm. The relation between density and stopping power are discussed using the reconstructed image.