arXiv subjects

Simona Giordanengo

Publications and source records attributed to Simona Giordanengo.

7 recordsLinked to original sources

arXiv2026

Prompt Gamma Timing for range verification with carbon ion irradiation: first experimental measurements and comparison with Geant4 Monte Carlo simulations

Prompt Gamma Timing (PGT) is a promising technique for in vivo range verification in particle therapy, exploiting the time-of-flight between primary particles and prompt gamma rays emitted by nuclear interactions. PGT distribution is highly sensitive to beam energy and target density, which, under controlled detector positioning, enables real-time monitoring of particle range, detection of morphological changes, and support for adaptive treatment strategies. This study investigates for the first time the application of PGT in carbon ion therapy. Measurements were performed using a dedicated detection system composed of a silicon strip sensor for primary ion timing and a LaBr3(Ce) read out by a SiPM for secondary radiation. Carbon ion beams with energies of 166.41, 268.86, and 398.84 MeV/u irradiated a homogeneous 30.0 cm PMMA target at CNAO. The secondary radiation detector was positioned at four off-beam positions to assess the robustness of the PGT technique. Simulations based on Geant4 were conducted for all configurations to evaluate agreement and predictive capability. A bin-by-bin comparison of experimental and simulated PGT intensities demonstrated strong agreement within the 95% confidence interval, with no incompatible bins at 166.41 MeV/u, at most 1% at 268.86 MeV/u, and up to 8% at 398.84 MeV/u, depending on detector position. Photons were identified as the dominant contribution to the detected signals, particularly for detector positions upstream with respect to the primary particle beam, minimizing signal contamination from neutrons and charged fragments. The validated experimental-simulation framework confirms the capability of the proposed PGT system to resolve energy-dependent differences and highlights its potential for detecting clinically relevant changes in the particle beam range, supporting further development toward real-time monitoring in carbon ion therapy.

physics.med-ph↗

arXiv2025

Stopping power monitoring during proton therapy by means of prompt gamma timing: first experimental results with a homogeneous phantom

Proton therapy's full potential is limited by uncertainties that prevent optimal dose distribution. Monitoring techniques can reduce these uncertainties and enable adaptive treatment planning. Spatiotemporal Emission Reconstruction from Prompt-Gamma Timing (SER-PGT) is a promising method that provides insights into both particle range and stopping power, whose calculation would normally require knowledge about patient tissue properties that cannot be directly measured. We present the first experimental results using a 226.9 MeV synchrotron-proton beam impinging on a homogeneous phantom at a sub-clinical intensity (2 - 4 x 10^7 pps). SER-PGT uses data from a multi-detector setup: a thin and segmented Low Gain Avalanche Diode for proton detection and Lanthanum Bromide-based crystals for photon detection. The estimated stopping power profile showed an 8% +- 3% average error compared to NIST PSTAR values, and 2% +- 2% deviation relative to water at 100 MeV. Range assessment in a phantom with a 4 cm air-gap successfully identified the range shift with a 3 mm standard deviation. These results demonstrate the feasibility of using SER-PGT to recover both range and stopping power information through particle kinematics and PGT measurements.

physics.med-ph↗

arXiv2024

Characterization of a modified clinical linear accelerator for ultra-high dose rate electron beam delivery

Irradiations at Ultra High Dose Rate (UHDR) regimes, exceeding 40 Gy/s in single fractions lasting less than 200 ms, have shown an equivalent antitumor effect compared to conventional radio-therapy with reduced harm to normal tissues. This work details the hardware and software modi-fications implemented to deliver 10 MeV UHDR electron beams with a Linear Accelerator Elekta SL 18 MV and the beam characteristics obtained. GafChromic EBT XD films and an Advanced Markus chamber were used for the dosimetry characterization, while a silicon sensor assessed the machine's beam pulses stability and repeatability. Dose per pulse, average dose rate and instantaneous dose rate in the pulse were evaluated for four experimental settings, varying the source-to-surface dis-tance and the beam collimation, i.e. with and without the use of a cylindrical applicator. Results showed dose per pulse from 0.6 Gy to a few tens of Gy and average dose rate up to 300 Gy/s. The obtained results demonstrate the possibility to perform in-vitro radiobiology experiments and test of new technologies for beam monitoring and dosimetry at the upgraded LINAC, thus contributing to the electron UHDR research field.

physics.med-ph↗

arXiv2023

Variation of the relative biological effectiveness with fractionation in proton therapy: analysis of prostate cancer response

Purpose: To present a methodology to analyze the variation of RBE with fractionation from clinical data of tumor control probability (TCP) and to apply it to study the response of prostate cancer to proton therapy. M&M: We analyzed the dependence of the RBE on the dose per fraction by using the LQ model and the Poisson TCP formalism. Clinical TCPs for prostate cancer treated with photon and proton therapy for conventional fractionation (2 Gy(RBE)x37 fractions), moderate hypofractionation (3 Gy(RBE)x20 fractions) and hypofractionation (7.25 Gy(RBE)x5 fractions) were obtained from the literature and analyzed. Results: The theoretical analysis showed three distinct regions with RBE monotonically decreasing, increasing or staying constant with the dose per fraction, depending on the change of ({\alpha}, \{beta}) values between photon and proton irradiation (the equilibrium point being at({\alpha}_p/\{beta}_p)=({\alpha}_X/\{beta}_X)({\alpha}_X/{\alpha}_p)). An analysis of the clinical data showed RBE values that decline with increasing dose per fraction: for low risk RBE=1.124, 1.119, and 1.102 for 1.82 Gy, 2.73 Gy and 6.59 Gy per fraction (physical proton doses), respectively; for intermediate risk RBE=1.119, and 1.102 for 1.82 Gy, and 6.59 Gy per fraction (physical proton doses), respectively. These values are nonetheless very close to the nominal 1.1 value. Conclusions: We presented a methodology to analyze the RBE for different fractionations, and we used it to study clinical data for prostate cancer. The analysis shows a monotonically decreasing RBE with increasing dose per fraction, which is expected from the LQ formalism and the changes in ({\alpha}, \{beta}) between photon and proton irradiation. However, the calculations in this study have to be considered with care as they may be biased by limitations in the modeling and/or by the clinical data set used for the analysis.

physics.med-ph↗

arXiv2022

A Compensated Design of the LGAD Gain Layer

In this contribution, we present an innovative design of the Low-Gain Avalanche Diode (LGAD) gain layer, the p$^+$ implant responsible for the local and controlled signal multiplication. In the standard LGAD design, the gain layer is obtained by implanting $\sim$ 5E16/cm$^3$ atoms of an acceptor material, typically Boron or Gallium, in the region below the n$^{++}$ electrode. In our design, we aim at designing a gain layer resulting from the overlap of a p$^+$ and an n$^+$ implants: the difference between acceptor and donor doping will result in an effective concentration of about 5E16/cm$^3$, similar to standard LGADs. At present, the gain mechanism of LGAD sensors under irradiation is maintained up to a fluence of $\sim$ 1-2E15/cm$^2$, and then it is lost due to the acceptor removal mechanism. The new design will be more resilient to radiation, as both acceptor and donor atoms will undergo removal with irradiation, but their difference will maintain constant. The compensated design will empower the 4D tracking ability typical of the LGAD sensors well above 1E16/cm$^2$.

physics.ins-det↗

arXiv2022

The CNAO Dose Delivery System for modulated scanning ion beam radiotherapy

This paper describes the dose delivery system used at the Centro Nazionale di Adroterapia Oncologica (CNAO) for ion beam modulated scanning radiotherapy. CNAO Foundation, INFN and University of Torino have developed and commissioned a Dose Delivery System (DDS) to monitor and guide ion beams accelerated by a synchrotron and to distribute the dose with a 3D scanning technique. The target volume, segmented in several layers orthogonally to the beam direction, is irradiated by thousands of pencil beams which must be steered and held to the prescribed positions until the prescribed number of particles has been delivered. At CNAO, these operations are performed by the DDS. The main components of this system are 2 independent beam monitoring detectors (BOX1 and BOX2), interfaced with 2 control systems performing real-time control, and connected to the scanning magnets and the beam chopper. As a reaction to any potential hazard, a DDS interlock signal is sent to the Patient Interlock System which immediately stops the irradiation. The tasks and operations performed by the DDS are described following the data flow from the Treatment Planning System through the end of the treatment delivery. The ability of the DDS to guarantee a safe and accurate treatment was validated during the commissioning phase by means of checks of the charge collection efficiency, gain uniformity of the chambers and 2D dose distribution homogeneity and stability. A high level of reliability and robustness has been proven by 3 years of system activity. The DDS described in this paper is one among the few worldwide existing systems to operate ion beam for modulated scanning radiotherapy. It has proven to guide and control the therapeutic pencil beams with accuracy and stability showing dose deviations lower than the acceptance threshold of 5% and 2.5% respectively during daily Quality Assurance measurements.

physics.med-ph↗

arXiv2018

Dose Delivery Concept and Instrumentation

Radiation therapy aims to deliver the prescribed amount of dose to a tumour at the same time as sparing the surrounding tissues as much as possible. In charged particle therapy, delivering the prescribed dose is equivalent to delivering the prescribed number of ions of a given energy at each position of the irradiation field. The accurate delivery is committed to a dose delivery (DD) system that shapes, guides and controls the beam before the patient entrance. Most of the early DD systems provided uniform lateral dose profiles by using different devices, mainly patient-specific, placed in the beam line to shape the three-dimensional final target dose. More recently, systems that provide highly conformal dose distributions using thousands of narrow beams at well-defined energy were developed which feature advanced scanning magnets and real-time beam monitors, without patient-specific hardware. This lecture will cover the general dose delivery concept as well as the different DD instrumentations depending mainly on the beam delivery technique and on the particle and accelerator types. Some characteristic worldwide DD and beam monitor systems will be mentioned.

physics.med-ph↗