Quantitative proton tomography: preliminary experiments.

An attempt has been made to see whether energetic protons (158 MeV) could be used instead of X-rays in computerized axial tomography to detect density differences of the order of those at which commercial X-ray tomographs cease to be useful. A circularly symmetrical phantom consisting of Lucite and sugar solutions was used, and density differences of 0-5% were reconstructed with reasonable accuracy from data obtained with very simple equipment. Discontinuities in either density or chemical composition, or both, seem to cause artifacts in the reconstruction. These may be related to the West-Sherwood effect.