2nd QGP International Research Center Seminar

by Dieter Rohrich (Department of Physics & Technology-University of Bergen)

Friday May 8, 2026, 2:00 PM → 3:30 PM Asia/Tokyo

University of Tsukuba, Natural Science Building B, Room 114

Title: Proton CT – quasi-online dose plan verification and online dose delivery monitoring

Abstract: A novel imaging modality using protons promises to improve the precision of cancer treatment in particle therapy. Being able to position the so-called Bragg peak accurately inside the tumor is a major advantage of using charged particles, but incomplete knowledge about a crucial tissue property, the stopping power, limits its precision. A proton/helium-CT scanner provides direct, quasi-online information regarding the stopping power and has the potential to reduce range uncertainties significantly. For a proton-CT scan the particles – typically protons or alpha particles - need to be energetic enough to traverse the patient completely. The trajectory of every outgoing proton, as well as the residual energy/range, is measured; protons impinging from different directions provide a 3D-map of the relative stopping power. A (clinical) prototype of a pCT-scanner is being constructed at the University of Bergen.  A complete CT reconstruction of a simulated anthropomorphic paediatric head phantom shows that a spatial resolution of 1-2 mm and a Water-Equivalent-Thickness (WET) precision of 1-2 mm can be achieved, sufficient for proton therapy treatment planning. During treatment, a shower of secondary particles is emitted into the forward region and thus into the acceptance of the pCT apparatus. Simulation studies with the head phantom show that by analysing the size and shape of the shower, the Bragg-peak inside the phantom can be localized with a sub-millimeter precision in real-time. Beam tests have confirmed this strong correlation between proton beam range and forward neutrons and gammas. 

pCT_Tsukuba_2026.pdf