Particle therapy beam monitoring with HV-CMOS sensors

Radiotherapy is an important pillar in the therapy of cancers and is prescribed to ~50% of cancer patients. Standard radiotherapy uses photon radiation whereas particle therapy uses high energy protons and carbon ions to destroy tumor cells in the body of patients. To achieve local tumor control a well-controlled particle beam in terms of position and dose is of utmost importance for the success of the therapy and the patient’s health. The beam control system requires precise and fast measurement of the dose and beam position which must be provided by the beam monitors. Currently, these are gas-filled detectors.

Looking at particle detectors in modern particle physics experiments we find solid-state devices, such as high-voltage complementary metal oxide semiconductor (HV-CMOS) sensors, are ubiquitous. They offer much better time and spatial resolution, which could be highly beneficial for use in a beam monitoring system for particle therapy. As ion beam therapy guided by magnetic resonance imaging (MR-guided) is being developed these days, HV-CMOS sensors shall be tested in the presence of magnetic fields. HV-CMOS sensors are thin (<150 μm) monolithic devices, which offer high spatial resolution and detection efficiency for ionizing particles as well as customizable on-chip data processing (like clustering, particle counting, signal charge integration, etc). Within this proposed project we want to explore the feasibility to apply this technology to the precise and fast monitoring of a therapeutic particle beam.

The two partners complement each other in an ideal way: the team from the Heidelberg Ion beam Therapy center (HIT) contributes the know-how on the beam delivery system and patient treatment, while the team from the Institute for Data Processing and Electronics (IPE) at KIT has proven expertise in delivering detector systems for extreme environments. HV-CMOS sensors have been pioneered by one of the PMs (I. Peric) and are being designed and developed at the KIT ASIC and Detector Lab (ADL) associated to the IPE.

Within this project an optimized test sensor will be designed and tested in beam at HIT. After successful evaluation of the pixel design a larger demonstrator sensor will be developed, which also includes the investigation of multi-sensor interconnection techniques to cover the required large area of 25 cm x 25 cm.

During this project we will also derive concepts for proper housing and mounting of the sensor as well as for a DAQ system capable to process and provide the required data for the therapy control system. These sensor developments and conceptual studies of the auxiliary systems will allow us to better quantify the budgetary needs and further development steps towards a prototype system for clinical use.

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