Cutting edge research in the treatment of tumours has oriented itself towards hadron therapy, one of the most effective external radiotherapy techniques, that uses a charged particle beam (protons and carbon ions) with energy comprised between 70 and 400 AMeV. In spatial terms, this means that such beams make it possible to release precisely the required dose to control the cancerous mass while at the same time leaving the surrounding healthy tissue almost totally untouched. If the maximum advantage is to be made of the potential of these beams, this property must be accompanied by information on the stopping power of the particles used for radio-therapy treatments.
The direct use of this information, rather than that from X-ray tomography, leads to a more accurate evaluation of the distribution of the dose. The radiographies transmitted can then be used to verify the positioning of the patient and, therefore, the availability of very accurate systems of imaging is of fundamental importance. We propose to develop new detection systems for the tracking with the aim of developing in the direction of real-time, large detection areas with high spatial and time resolutions, having extremely important therapeutic applications. In details, a large-area structure is proposed, up to 40 x 40 sq cm, consisting in a ribbon of scintillating fibres positioned in the classic bi-dimensional scheme but extracting their information in an original, absolutely innovative way, using a reduced number of electronics channels that can reveal the crossing position of the particles with a very accurate spatial resolution. The choice of the photo-sensor to use for converting the optical signal coming from the fibres into electrical signals will be carried out by optimization, which means that various light detection technologies must be studied and characterised. Information regarding the energy released in this interaction will be also extracted in real-time from the same tracker. The entire system will be planned on a modular basis so that, with the necessary modifications it can be adapted for other different applications (PET, Security/Safety, static and dynamic material analyses, Nuclear scattering, the aerospace field).
The aim is to take advantage of new detection techniques to develop an imaging system for charged particles based on the consolidated principle of measuring the residual range. The objectives for such a system are large dimensions (up to 40x40 sq cm), high spatial resolution (up to approximately 100 micron) and high time resolution (up to 1.5 ns) and the capacity to acquire complex images at a rate of 30 MHz which are exceptionally important in clinical and oncology therapies.
We have applied to patent this idea and the application is going through. In order to attain the objectives and make the correct choices, accurate simulations of the detector and each constituent part of it, as well as a precise characterization of the various types of fibres and scintillators available on the market have been carried out and are still on course. Studies have been carried out regarding fibre manipulation techniques and the optical connection of the latter to photo-sensors. A more detailed task has been also necessary in order to simplify the construction and mechanical assembly of this delicate set of devices. The prototypes developed have been accurately tested using radioactive sources and particle beams that are available next door in the Laboratori Nazionali del Sud (LNS) of the Istituto Nazionale di Fisica Nucleare (INFN). The test results will be used to optimize the final detector.