Gamma-ray computed tomography system with a double-sided strip detector

We have developed a gamma-ray computed tomography system using a CdTe double-sided strip detector. Owing to a 250 mu m fine strip pitch and high energy resolution with photon-counting capability, the system provides highly accurate images, with which the materials and their distribu-tions inside the target can be determined according to the photon transmittances. We evaluated the key performance of the system, conducting transmission measurements for Al, Cu, and Pb plates and also for Al, Fe, Cu, and Pb rod-phantoms, both using X-rays (-30 keV) and gamma-rays (-80 keV) from a 133Ba source. The measured transmittances agreed well with the calculated values from simulations. We successfully reconstructed the three-dimensional structure of the rod-phantom and distinguished the elements inside the phantom. Compared with the simulated photon transmit-tances, we found that material identification based on tomographic images obtained with the system is efficient as long as the target object does not contain thick high-Z elements.