Design and prototyping of HTS magnets for medical gantry applications (GaToroid)

Design and prototyping of HTS magnets for medical gantry applications (GaToroid)

GaToroid is an innovative gantry design based upon a toroidal magnet concept, which eliminates the need to rotate the structure. The gantry comprises a set of discrete superconducting coils constituting the toroidal magnet, and a bending device at the entrance of the structure. 

By selecting the impinging angle of beams with different momentum values, it is possible to reach different spots (if beams have same entry point) or to get a focusing effect (if beams enter the magnet from different angles).   

GaToroid is meant to be lightweight: if used with proton beams, the structure would have an outer diameter of about 3.2m, for a total weight estimated around 12 tons. For carbon ion beams, the outer diameter would be of the order of 5m, for a total weight of around 50 tons. This represents a substantial weight reduction compared to conventional gantries, which weights around 100 tons for protons and over 350 tons for carbon ions.

Since this system works in steady state with no rotation, it can fully exploit the potential of superconductors, having no limitations by current or system’s movement.

In 2017 funding for a PhD student for 3 years was granted. The aim was to investigate alternative geometries for magnetic gantries, especially fixed configurations, and develop HTS-based design that may reduce volume, weight and cost by a significant factor (target 3 to 5 times) with respect to existing normal- and superconducting realizations. A scaled single coil demonstrator will then be designed, manufactured and tested. 

GaToroid is still a concept that must be further validated before an actual implementation can be considered. Scoping studies (supported by the MA budget at the level of a PhD student and by ATTRACT funding) are on-going for an initial, compact version. Clinical validation is being pursued for a cost-optimized version for ion therapy at CNAO. The proposed project pursues the technical validation of a specific coil design for ion therapy in LTS (Nb-Ti) by building a demonstrator with scaled dimensions (approximately 1:5) and operating parameters (approximately 1/2 current, identical field). The demonstrator will be tested in liquid helium and the magnetic field in the coil gap will be mapped.

In 2019 additional funding for this Nb-Ti GaToroid Demonstrator was granted.