The H2I2 proposal aims at designing an innovative integrated imaging system that could disrupt the field of particle therapy by providing a lightweight, cost effective, and highly performant solution to the major challenges in precise delivery of the dose to the patient.

Particle therapy is an advanced form of radiation therapy, which uses beams of protons or heavier ions to treat tumours. Its intrinsic advantage lies in the characteristic dose deposition of ions as a function of the depth of tissue traversed: while X-rays lose energy slowly and mainly exponentially as they penetrate tissue, hadrons deposit almost all of their energy in a sharp peak – the Bragg peak – at the very end of their path. As a consequence, the dose delivered to the cancer tissue can be maximised while at the same time preserving the surrounding healthy tissues.

Exploiting the full potential of particle therapy requires absolute control of the dose delivered to the patient: unfortunately, all the main components required to optimally implement particle therapy – beam delivery, beam monitoring and range monitoring – suffer from important limitations that prevent a real-time verification of the compliance between the treatment planning and delivery. H2I2 will not only design a high-precision in vivo imaging system, which is currently unavailable in any particle therapy centre, but will also fully integrate it in the beam delivery and dramatically reduce the footprint and complexity of the treatment room.

This ambitious goal will be reached by a clever combination of innovative concepts and novel technologies, well beyond the state of the art:

– beam delivery obtained with a completely new approach based on a static toroidal gantry;
– beam monitoring obtained with high timing resolution pixelated silicon detectors;
– online range monitoring with a PET/prompt gamma hybrid detector;
– an insert that will complete the functionality by implementing a proton Computed Tomography for pre-treatment fast position verification.

The proposed concept is highly innovative, as it would design for the first time ever a fully integrated delivery and monitoring system. From the point of view of the performance, it would allow:

– highly flexible and fast beam delivery, with a static gantry much lighter and smaller than the existing ones, subjected to no restrictions on beam timing, beam energy or positioning precision associated to its movement;
– beam monitoring with single particle counting capability for fast measurement of beam fluence and position;
– online range monitoring by means of a 3D measurement of the beam-induced activity distribution and of the prompt gamma emission profile, with the goal of an overall range precision of about 1mm obtained within 1 minute of the treatment delivery start.

The project endpoint will be an optimised design of the integrated system, with a reliable assessment of its expected performance obtained through Monte Carlo simulations. Such design could be the starting point for the construction and commissioning of a prototype system, based on the innovative combination of consolidated and novel imaging techniques, that would allow the implementation of
adaptive particle therapy protocols, by remarkably increasing the control on the treatment planning vs. delivery compliance.