[1] German Res Ctr Environm Hlth, Helmholtz Zentrum Munchen, Inst Radiat Protect, D-85764 Neuherberg, Germany
[2] Lund Univ, Malmo Univ Hosp, SE-21100 Malmo, Sweden
[3] Univ Milan, Dept Phys, I-20122 Milan, Italy
[4] Jozef Stefan Inst, Expt Particle Phys Dept, SI-1001 Ljubljana, Slovenia
[5] CSIC, Inst Fis Corpuscular, E-46071 Valencia, Spain
[6] Scivis Wissensch Bildverarbeitung GmbH, D-37085 Gottingen, Germany
[7] Univ Michigan, Dept Radiol, Ann Arbor, MI 48109 USA