Preliminary Risk Analysis of a Superconducting Gantry for Hadron Therapyv

Hadron therapy offers one of the most advanced options for cancer treatment. If compared with conventional photon radiotherapy, its advantage resides in the properties of hadrons, as protons and heavier ions, to treat deep-seated tumors with precise dose deposition, while sparing the surrounding healthy tissues. An effective implementation of hadron therapy is the use of a beamline rotating around the patient, namely a gantry. A gantry irradiates the tumor from different angles with advantages with respect to fixed beamlines. The use of the gantry in combination with heavy ions such as carbon allows for even superior treatment capabilities. At present, this solution is a considerable engineering challenge, because of the size, weight, and cost of the magnets, as well as of the overall infrastructure. In the context of the European project HITRIplus, several research institutes and clinical centers are studying and developing a compact and affordable gantry for hadron therapy with carbon ions by using superconducting magnets. The superconducting technology allows for a significant reduction in magnet size and weight with respect to normal-conducting magnets. Nonetheless, it suffers from the risk of quenching, i.e. the loss of the superconductive state, with potential damage to beamline components and consequent treatment disruption. This paper presents the results of a preliminary risk analysis of the superconducting gantry technology aiming to define design requirements for mitigating the risks and limiting their consequences by adopting several risk controls measures. An additional goal of the paper is to identify and address the design trade-offs that concern patient safety and operability. Finally, superconducting and normal-conducting gantry technologies are compared with the intent of summarizing benefits and risks.

Keywords: Risk analysis, Safety, Medical devices, Particle therapy accelerators technology.