Ricerc@Sapienza

Proton and carbon ion beams are used in the clinical practice for external radiotherapy treatments
achieving, for selected indications, promising and superior clinical results with respect to x-ray based
radiotherapy. Other ions, like 4 He have recently been considered as projectiles in particle therapy centres
and might represent a good compromise between the linear energy transfer and the radiobiological
effectiveness of 12 Cion and proton beams, allowing improved tumour control probability and
minimising normal tissue complication probability. All the currently used p, 4 He and 12 C ion beams
allow achieving sharp dose gradients on the boundary of the target volume, however the accurate dose
delivery is sensitive to the patient positioning and to anatomical variations with respect to photon
therapy. This requires beam range and/or dose release measurement during patient irradiation and
therefore the development of dedicated monitoring techniques. All the proposed methods make use of
the secondary radiation created by the beam interaction with the patient and, in particular, in the case of
12 C ion beams are also able to exploit the significant charged radiation component.
Measurements performed to characterise the charged secondary radiation created by 12 C and 4He
particle therapy beams are reported. Charged secondary yields, energy spectra and emission
profiles produced in a poly-methyl methacrylate (PMMA) target by 4 He and 12 C beams of different
therapeutic energies were measured at 60 ° and 90 ° with respect to the primary beam direction. The
secondary yield of protons produced along the primary beam path in a PMMA target was obtained.
The energy spectra of charged secondaries were obtained from time-of-flight information, whereas
the emission profiles were reconstructed exploiting tracking detector information. The obtained
measurements are in agreement with results reported in the literature and suggests the feasibility
of range monitoring based on charged secondary particle detection: the implications for particle
therapy monitoring applications are also discusse