The MONDO Tracker: Characterisation and Study of Secondary Ultrafast Neutrons Production in Carbon Ion Radiotherapy

M Toppi ,Patrizia De Maria,Marco Magi,Leonardo Gasparini,Micol De Simoni,Enrico Manuzzato,Matteo Perenzoni,Luca Parmesan,Yunsheng Dong,R Mirabelli ,V Patera ,A Schiavi ,I Mattei ,S Muraro ,S.m Valle ,G Franciosini ,G Traini ,A Sarti ,M Fischetti ,G Battistoni ,A Sciubba ,Alessandro Bochetti ,M Marafini

doi:10.3389/fphy.2020.567990

Abstract

Secondary neutrons produced in Particle Therapy (PT) treatments are responsible for the delivery of a large fraction of the out-of-target dose as they feebly interact with the patient body. To properly account for their contribution to the total dose delivered to the patient, a high precision experimental characterisation of their production energy and angular distributions is eagerly needed. The experimental challenge posed by the detection and tracking of such neutrons will be addressed by the MONDO tracker: a compact scintillating fibres detector exploiting single and double elastic scattering interactions allowing for a complete neutron four momentum reconstruction. To achieve a high detection efficiency while matching the fibres (squared, 250 $\mu$m side) high granularity, a single photon sensitive readout has been developed using the CMOS based SPAD technology. The readout sensor, with pixels of $125\times250 \micro\meter^2$ size, will be organised in tiles covering the full detector surface and will implement an auto-trigger strategy to identify the events of interest. The expected detector performance in the context of neutron component characterisation in PT treatments delivered using carbon ions has been evaluated using a Monte Carlo simulation accounting for the detector response and the neutrons production spectra.

Highlights

Particle therapy (PT) is a modern technique of solid tumor treatment that exploits the energy deposit of charged light ion beams, highly localised in the target region defined as “Bragg-Peak,” to preserve the healthy tissues
We present the evaluation of the expected performance using a detailed MC simulation of the neutrons production during a carbon ion particle therapy (PT) treatment
The potential of the MONDO tracker in characterising the neutrons produced in a PT treatment with carbon ions has been explored using neutrons from a point-like source placed 20 cm from the detector face, according to the energy spectrum of neutrons produced in PT conditions

Summary

Introduction

Particle therapy (PT) is a modern technique of solid tumor treatment that exploits the energy deposit of charged light ion beams, highly localised in the target region defined as “Bragg-Peak,” to preserve the healthy tissues. The MONDO Tracker Characterisation secondary neutrons can deposit an absolute nonnegligible energy in and out of field even far away from the target volume (voxel) as they are weakly interacting with the patient’s body [1 2]. Their contribution has to be taken into account with the highest possible precision when performing the treatment plan optimisation and evaluating the dose absorbed by the organs at risk. To this aim, a high precision experimental characterisation of the secondary neutron spectra and fluxes is eagerly needed. Tracking the primary neutrons produced by the PT beam interactions with the patient tissues, which have energies of hundreds of MeV, is extremely challenging from the experimental point of view

Methods

Results

Conclusion