1. International Tomography Center, Novosibirsk 630090, Russia
2. Novosibirsk State University, Novosibirsk 630090, Russia
3. NVision-Imaging Technologies, Ulm 89081, Germany
4. Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany
5. Helmholtz-Institut, GSI Helmholtzzentrum für Schwerionenforschung, 55128 Mainz, Germany
6. Department of Physics, University of California, Berkeley, California 94720, USA