Development of the proton CT system based on Low Gain Avalanche Detectors

The project aims at conceptual design and full simulation of proton Computer Tomography (pCT) apparatus based on use of Low Gain Avalanche Detectors (LGAD). The pCT exploits the measurement of proton trajectory through the investigated volume and measurement of the exiting proton energy to reconstruct the most likely path (MLP) of the proton in the investigated volume. These paths are used to reconstruct the image. Such process significantly eases the proton irradiations as not only a more accurate image is obtained at given dose, but also opens possibility for better treatment control and imposes less stress to the patient. The main advantage of using the LGADs is the fact that unlike current pre-clinical prototypes doesn’t use “calorimeter”/”range finder” to determine the energy of the exiting protons, but determines the energy of the protons from the time-of-flight between two detector layers. The offers a significant simplification as a single detector technology can be used and having a spatial and timing information from all three detector layers opens a possibility to improved MLP reconstruction algorithms, which may offer another advantage over present prototypes.

We plan to setup a full GEANT4 simulation to simulate the operation of such pCT to study improved MLP reconstruction algorithms and benchmark the performance against conventional designs. Moreover, the simulation will be used to verify the measurements using LGAD prototype sensors. Prototype detectors developed for particle physics will be tested and evaluated with adequately fast electronics and compared to the simulation. The laboratory setup will be constructed with 3 layers of LGAD sensors mounted on the boards with fast electronics. A full motorized positioning of the planes and construction of phantoms will allow the measurements of most likely path of 90Sr electrons in the thin water phantom. The setup will be versatile and will be used also in the proton test beam where more complex phantoms will be used and most important properties of the system verified with simulations. The main focus will be determining the energy resolution of protons, geometrical positioning of sensor planes and ways that LGAD based system can be used in clinical studies. The first tests will be conducted with the sensors and electronics that are already at our hands. The results obtained from tests and simulations will steer the design and geometry of further prototype sensors.