Clinical prototype of a proton CT based on a tracking calorimeter

In recent decades there has been a worldwide increase in the number of cancer patients treated with proton and carbon radiation therapy. Norway is presently constructing two regional particle therapy facilities, with the aim of clinical startup within the next three years. Particle therapy as of today is performed with the delivery of pre-calculated dose plans for each patient. The applied dose plans are based on X-ray computed tomography (CT) images. CT images reflect the patient's anatomy in an excellent manner; however, they yield a limited basis for the calculation of the energy deposition of ions in the patient's body. Here lies the benefit of the proposed proton CT: its data will considerably improve the dose planning, position verification and dose deposition verification. The project will allow to explore the full potential of ion therapy and bring the concept of proton radiography and pCT into the clinical domain. The proposed novel clinical pCT-prototype combines a tracker and a calorimeter in a single compact device. The key components, Monolithic Active Pixel Sensors (MAPS), have been thoroughly characterized in proton and Helium beams. The mechanical structure and the cooling system has been assembled. The readout electronics has been designed and prototypes have been tested. All sensors have been produced and tested and the assembly of the scanner is ongoing. A full reconstruction chain, from the detector response to the 3D tomography has been established and was successfully tested with simulated data.

In the recent decades there has been a worldwide increase in the number of cancer patients treated with proton and carbon radiation therapy. Norway is presently planning 3-4 regional particle therapy facilities, with the aim of clinical startup within the next 5-6 years. Particle therapy as of today is performed with the delivery of pre-calculated dose plans for each patient. The applied dose plans are based on x-ray computed tomography (CT) images. CT images reflect the patient's anatomy in an excellent manner; however, they yield a limited basis for the calculation of the energy deposition of ions in the patient's body. For dose planning, position verification and dose deposition verification purposes it is important to develop imaging based on proton CT data. The project will allow to explore the full potential of ion therapy and bring the concept of proton radiography and pCT into the medical domain. We propose to develop a novel clinical pCT-prototype combining a tracker and a calorimeter in a single compact device. The pCT prototype will be a three-dimensional tracker consisting almost solely of many silicon sensor layers, enhanced with some absorber material to improve the capability of range measurements of somewhat higher energy particles. Unlike previous attempts to implement a pCT by using multiple detectors, our instrument will be a single device performing tracking, particle identification and energy/range measurements simultaneously. Because of the extremely large number of cells the device will be able to cope with a large amount of particles simultaneously, thus providing a breakthrough in rate capabilities. In addition, by using the same granularity throughout, the problem of matching track and energy measurements is non-existent.