Medical Physics: development of tools for radiotherapy
The group is active since 1992 in the development of hardware and software tools for radio- and particle-therapy, with the goal of bringing into clinical environment and transferring to industry the know-how acquired in fundamental physics research. Hardware development began with design and construction of parallel plate ionization chambers segmented in strips and pixels for particle therapy, leading to the construction of the Dose Delivery System (DDS) of the National Centre of Oncological Hadrontherapy (CNAO, Pavia).
During a two year project named RIDOS (Real-time Ion DOse planning and delivery System) a new system has been developed, able to interface a GPU-based forward-dose calculation with the CNAO DDS and with a patient-motion tracking system to perform online dose verification for scanned ion beam therapy.
At present, the group is involved in the MoVeIT INFN project and the research activities are focused on Ultra-Fast Silicon Detectors (UFSD) and VLSI microelectronics to develop two prototypes of new beam monitor for radiobiological applications at three irradiation facilities in Italy: CATANA (Catania), CNAO and TIFPA (Trento).
The first prototype consists of a 3x3 cm2 detector based on 50 μm thick UFSDs, segmented in strips and designed to count individual protons at current clinical rate, thanks to the development of a dedicated front-end electronics.
UFSDs have been selected because of their large signal-to-noise ratio and fast collection time in small thicknesses (1 ns in 50 µm). Such a device allows the direct count of number of particles going through the sensitive area, improving the indirect count obtained through measurement of ionization charge, as routinely performed in conventional beam monitors based on parallel plate ionization chambers. The second prototype is intended to measure the beam energy with time-of-flight techniques, using a telescope of two UFSD sensors segmented in a minimum number of pads. The clinical requirements need to achieve an energy resolution corresponding to a range error less than 1 mm for the wide energy range in use (60-250 MeV proton beam).
Dedicated readout electronics is under test and development for the particle counter. The new VLSI chip, named ABACUS, was designed to be able to read the UFSD signals, which are very short (1-2 ns), and is based on a scheme where the preamplifier is followed by a discriminator with a threshold which could be set. Out of the discriminator, the pulses are sent to an FPGA which implements pulse counting and also pile up corrections algorithms. The requirements are extremely demanding because the front-end input charge is expected to be between 3 fC and 140 fC, the pulses frequency between 2 MHz and 200 MHz. Two different ASICs have been designed and manufactured: one based on Charge sensistive amplifier the other one on Transimpedence amplifier. ABACUS will be the heart of the TERA10 chip, that will read-out the UFSDs in the final system.
Prodotti della ricerca
RIDOS: A new system for online computation of the delivered dose distributions in scanning ion beam therapy - Physica Medica 60 (2019) 139
Dose detectors, sensors and their applications, Special Issue Medical Physics 45 (11), (2018)
Innovative thin silicon detectors for monitoring of therapeutic proton beams: Preliminary beam tests, Journal of Instrumentation 12, (2017) 12, C12056
Review of technologies and procedures of clinical dosimetry for scanned ion beam radiotherapy, Physica Medica 43 (2017) 79-99
Design and characterization of a 64 channels ASIC front-end electronics for high-flux particle beam detectors, Nuclear Instruments and Methods in Physics Research A 867 (2017)1-6
The CNAO Dose Delivery System for ion pencil beam scanning radiotherapy, Medical Physics 42, 1 (2015) 263
Design optimization of ultra-fast silicon detectors, Nuclear Instruments and Methods in Physics Research A 796, (2015) 141-148
A simple method to increase the current range of the TERA chip in charged particle therapy applications, Nuclear Instruments and Methods in Physics Research A 798, (2015) 107-110