Showing papers by "Silvia Muraro published in 2018"

Secondary radiation measurements for particle therapy applications: charged particles produced by 4He and 12C ion beams in a PMMA target at large angle.

Abstract: Proton and carbon ion beams are used in the clinical practice for external radiotherapy treatments achieving, for selected indications, promising and superior clinical results with respect to x-ray based radiotherapy. Other ions, like [Formula: see text] have recently been considered as projectiles in particle therapy centres and might represent a good compromise between the linear energy transfer and the radiobiological effectiveness of [Formula: see text] ion and proton beams, allowing improved tumour control probability and minimising normal tissue complication probability. All the currently used p, [Formula: see text] and [Formula: see text] ion beams allow achieving sharp dose gradients on the boundary of the target volume, however the accurate dose delivery is sensitive to the patient positioning and to anatomical variations with respect to photon therapy. This requires beam range and/or dose release measurement during patient irradiation and therefore the development of dedicated monitoring techniques. All the proposed methods make use of the secondary radiation created by the beam interaction with the patient and, in particular, in the case of [Formula: see text] ion beams are also able to exploit the significant charged radiation component. Measurements performed to characterise the charged secondary radiation created by [Formula: see text] and [Formula: see text] particle therapy beams are reported. Charged secondary yields, energy spectra and emission profiles produced in a poly-methyl methacrylate (PMMA) target by [Formula: see text] and [Formula: see text] beams of different therapeutic energies were measured at 60° and 90° with respect to the primary beam direction. The secondary yield of protons produced along the primary beam path in a PMMA target was obtained. The energy spectra of charged secondaries were obtained from time-of-flight information, whereas the emission profiles were reconstructed exploiting tracking detector information. The obtained measurements are in agreement with results reported in the literature and suggests the feasibility of range monitoring based on charged secondary particle detection: the implications for particle therapy monitoring applications are also discussed.

Analysis of time-profiles with in-beam PET monitoring in charged particle therapy

Abstract: Background: Treatment verification with PET imaging in charged particle therapy is conventionally done by comparing measurements of spatial distributions with Monte Carlo (MC) predictions. However, decay curves can provide additional independent information about the treatment and the irradiated tissue. Most studies performed so far focus on long time intervals. Here we investigate the reliability of MC predictions of space and time (decay rate) profiles shortly after irradiation, and we show how the decay rates can give an indication about the elements of which the phantom is made up. Methods and Materials: Various phantoms were irradiated in clinical and near-clinical conditions at the Cyclotron Centre of the Bronowice proton therapy centre. PET data were acquired with a planar 16x16 cm$^2$ PET system. MC simulations of particle interactions and photon propagation in the phantoms were performed using the FLUKA code. The analysis included a comparison between experimental data and MC simulations of space and time profiles, as well as a fitting procedure to obtain the various isotope contributions in the phantoms. Results and conclusions: There was a good agreement between data and MC predictions in 1-dimensional space and decay rate distributions. The fractions of $^{11}$C, $^{15}$O and $^{10}$C that were obtained by fitting the decay rates with multiple simple exponentials generally agreed well with the MC expectations. We found a small excess of $^{10}$C in data compared to what was predicted in MC, which was clear especially in the PE phantom.

Scintillating Fiber Devices for Particle Therapy Applications

Abstract: Particle therapy (PT) is a radiation therapy technique in which solid tumors are treated with charged ions and exploits the achievable highly localized dose delivery, allowing to spare healthy tissues and organs at risk. The development of a range monitoring technique to be used online, during the treatment, capable to reach millimetric precision is considered one of the important steps toward an optimization of the PT efficacy and of the treatment quality. To this aim, charged secondary particles produced in the nuclear interactions between the beam particles and the patient tissues can be exploited. Besides charged secondaries, neutrons are also produced in nuclear interactions. The secondary neutron component might cause an undesired and not negligible dose deposition far away from the tumor region, enhancing the risk of secondary malignant neoplasms that can develop even years after the treatment. An accurate neutron characterization (flux, energy and emission profile) is, hence, needed for a better evaluation of long-term complications. In this contribution, two tracker detectors, both based on scintillating fibers, are presented. The first one, named dose profiler (DP), is planned to be used as a beam range monitor in PT treatments with heavy ion beams, exploiting the charged secondary fragments production. The DP is currently under development within the Innovative Solutions for In-Beam DosimEtry in Hadrontherapy project. The second one is dedicated to the measurement of the fast and ultrafast neutron component produced in PT treatments, in the framework of the monitor for neutron dose in hadrontherapy project. Results of the first calibration tests performed at the Trento Protontherapy Center and at Centro Nazionale di Adroterapia Oncologica (Italy) are reported, as well as simulation studies.

In-room performance evaluation of a novel online charged secondary particles monitor of light ions PT treatments

Abstract: The advantages of using C, He and O ions as therapeutical beam particles in Particle Therapy is related to their enhanced Relative Biological Effectiveness and Oxygen Enhancement Ratio, resulting in an improved efficacy in damaging the cancerous cells. However, an accurate on-line control of the dose release spatial distribution is required to spare the healthy tissues surrounding the tumor area, preventing undesired damages caused by, for example, morphological changes occurred in the patient during the treatment with respect to the initial CT scan. This monitor technology is currently missing in clinical practice, and several studies are being performed to develop beam range verification systems exploiting the detection of the emitted secondary radiation. Charged secondary particles, produced by the projectile fragmentation in the collisions with the patient tissues, represent an interesting chance for C, He and O treatments since they are also emitted at large angles with respect to the beam direction and can be detected with high efficiency in a nearly background free environment. The Dose Profiler detector is a scintillating fibre tracker that allows an online charged fragments reconstruction and backtracking. The construction and preliminary tests performed on the DP, carried out using the Carbon ions beam of the CNAO treatment centre using an anthropomorphic phantom as a target, will be reviewed in this contribution.