Speaker
Description
The secondary neutrons produced in Particle Therapy treatments can travel along the path inside the patient and contribute with additional dose in-and out-of-field. This unwanted dose increases the risk of developing secondary cancers: late insurgences are particularly crucial in paediatric patients where the closeness of the organs and the recurrence onset strongly impacts the life expectation and quality [1].
A precise measurements of neutron flux, spectra and angular distributions is eagerly needed so to predict the normal tissue toxicity in the target region and the risk of late complications in the whole body.
Nowadays, no existing detector is able to separate efficiently the secondary neutrons from the ternary neutral component generated in the iterative interactions of fragmentation products with the treatment room (walls, nozzle, etc…) and the patient itself.
MONDO is a tracker tailored for the ultra-fast neutron detection in the [20-400] MeV energy range [2]. The detector, based on the reconstruction of the recoil protons produced in two consecutive (n,p) elastic scattering interactions (DES events), is a matrix of thin scintillating fibers (~250 µm side), arranged in layers orthogonally oriented, for a total size of 16x16x20 cm$^3$.
An innovative silicon SPAD based sensor with integrated electronics has been designed for the detector readout (SBAM sensor [3]) in collaboration with Fondazione Bruno Kessler. The MONDO performance has been evaluated by means of a Monte Carlo simulation developed in FLUKA: a detection efficiency of 10$^{-2}$ -10$^{-3}$ is expected for single and double elastic scattering respectively. The achievable relative energy resolution for the reconstructed neutrons is ~8% and the expected back-pointing resolution is < 1 cm (for a neutron source placed at 20 cm from the detector).
The MONDO detector, its expected performance and the readout calibration results with a matrix prototype will be presented.
[1] W. Newhauser and M. Durante, “Assessing the risk of second malignancies after modern radiotherapy” Nat. Rev. Cancer. 11 (2011) 438
[2] M. Marafini et al., “MONDO: a neutron tracker for Particle Therapy secondary emission characterization” Phys. Med. Biol. 62 (2017)
[3] R. Mirabelli et al., “The MONDO detector prototype development and test: steps towards a SPAD-CMOS based integrated readout (SBAM sensor)” Trans. on Nucl. Science 65 (2018)
