No abstract

Proton therapy is a precise forms of radiation therapy that makes use of high energy proton compared to the conventional, more commonly used and less precise x-ray and electron beams. On the other hand, to fully exploit the proton therapy advantages, very accurate quality controls of the treatments are required. These are mainly related to the dose calculations and treatment planning. Actually dose calculations are routinely performed on the basis of X-Ray computed tomography while a big improvement could be obtained with the direct use of protons as the imaging system.In this work we report the results of Monte Carlo simulations for the study of an imaging system based on the use of high energy protons: the proton Computed Tomography (pCT). The main limitation of the pCT and the current adopted technical solutions, based on the use of the Most Likely Path (MLP) approximation are illustrated. Simulation results are compared with experimental data obtained with a first prototype of pCT system tested with 200 MeV proton beams available at the Loma Linda University Medical Center (LLUMC) (CA).

We report the results of a beam experiment to develop proton Computed Tomography (pCT). The setup consists of telescopes of silicon strip detectors at the entrance and exit of a phantom to predict the path of the proton within the phantom and of a crystal calorimeter to measure the proton energy loss with high precision. The energy loss permits calculating the integrated proton stopping power along each proton path from which the electron density distribution can be reconstructed. We describe the 2D-image reconstruction of a lowcontrast phantom, derive the relationship between contrast, pixel size, and dose, and study the spatial resolution achievable with this setup .

A novel position-and energy-sensitive particle detector for radiobiological application is described. The aim is to support research in radiation response of biological systems, for example in the induction of mutations in C. elegans, where precise knowledge of location and intensity of the radiation is crucial to understand radiation sensitivity of individual cells. The "Particle Tracking Silicon Microscope" (PTSM) consists of a silicon strip detector in direct contact with radiobiological samples (e.g., C. elegans), such that the location and intensity of particle radiation can be controlled at the 10 m scale. The readout is performed with low-noise readout electronics, which allows the determination of the particle's position from the hit strip address and its energy from the specific energy loss. In our implementation, the energy loss is measured through the time-over-threshold (TOT). The noise rate at acceptable thresholds is so low that the single particles can be detected with 100% efficiency. The performance of the front-end ASIC is described, and the results of initial environmental tests are reported. These include placing biological samples and saline solutions in direct contact with the silicon detectors.Index Terms-Biomedical applications of radiation, silicon radiation detectors.

Proton therapy is a precise form of radiation therapy and thus it requires accurate quality control of patients treatment. Protons may be more suitable than conventional x rays for this task since the relative electron density distribution can be measured directly with proton Computed Tomography (pCT). However, proton CT has its own limitation. The main limit is that of spatial resolution limited by Multiple Coulomb Scattering of proton inside the body of patient. In order to improve spatial resolution we need to determine the most likely path of single proton inside the body. In this work we realized a set of Monte Carlo simulations for the calculation of the most likely path.