Purpose:
This paper describes the system for the dose delivery currently used at the Centro Nazionale di Adroterapia Oncologica (CNAO) for ion beam modulated scanning radiotherapy.
Methods:
CNAO ...Foundation, Istituto Nazionale di Fisica Nucleare and University of Torino have designed, built, and commissioned a dose delivery system (DDS) to monitor and guide ion beams accelerated by a dedicated synchrotron and to distribute the dose with a full 3D scanning technique. Protons and carbon ions are provided for a wide range of energies in order to cover a sizable span of treatment depths. 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. For the CNAO beam lines, these operations are performed by the DDS. The main components of this system are two independent beam monitoring detectors, called BOX1 and BOX2, interfaced with two control systems performing the tasks of real‐time fast and slow control, and connected to the scanning magnets and the beam chopper. As a reaction to any condition leading to a potential hazard, a DDS interlock signal is sent to the patient interlock system which immediately stops the irradiation. The essential 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.
Results:
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 three years of system activity needing rarely more than regular maintenance and working with 100% uptime. Four identical and independent DDS devices have been tested showing comparable performances and are presently in use on the CNAO beam lines for clinical activity.
Conclusions:
The dose delivery system described in this paper is one among the few worldwide existing systems to operate ion beam for modulated scanning radiotherapy. At the time of writing, it has been used to treat more than 350 patients and it has proven to guide and control the therapeutic pencil beams reaching performances well above clinical requirements. In particular, in terms of dose accuracy and stability, daily quality assurance measurements have shown dose deviations always lower than the acceptance threshold of 5% and 2.5%, respectively.
The calculation algorithm of a modern treatment planning system for ion-beam radiotherapy should ideally be able to deal with different ion species (e.g. protons and carbon ions), to provide relative ...biological effectiveness (RBE) evaluations and to describe different beam lines. In this work we propose a new approach for ion irradiation outcomes computations, the beamlet superposition (BS) model, which satisfies these requirements. This model applies and extends the concepts of previous fluence-weighted pencil-beam algorithms to quantities of radiobiological interest other than dose, i.e. RBE- and LET-related quantities. It describes an ion beam through a beam-line specific, weighted superposition of universal beamlets. The universal physical and radiobiological irradiation effect of the beamlets on a representative set of water-like tissues is evaluated once, coupling the per-track information derived from FLUKA Monte Carlo simulations with the radiobiological effectiveness provided by the microdosimetric kinetic model and the local effect model. Thanks to an extension of the superposition concept, the beamlet irradiation action superposition is applicable for the evaluation of dose, RBE and LET distributions. The weight function for the beamlets superposition is derived from the beam phase space density at the patient entrance. A general beam model commissioning procedure is proposed, which has successfully been tested on the CNAO beam line. The BS model provides the evaluation of different irradiation quantities for different ions, the adaptability permitted by weight functions and the evaluation speed of analitical approaches. Benchmarking plans in simple geometries and clinical plans are shown to demonstrate the model capabilities.
Ultra-fast silicon detectors Sadrozinski, H. F.-W.; Ely, S.; Fadeyev, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2013, Letnik:
730
Journal Article
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We propose to develop a fast, thin silicon sensor with gain capable to concurrently measure with high precision the space (∼10μm) and time (∼10ps) coordinates of a particle. This will open up new ...application of silicon detector systems in many fields. Our analysis of detector properties indicates that it is possible to improve the timing characteristics of silicon-based tracking sensors, which already have sufficient position resolution, to achieve four-dimensional high-precision measurements. The basic sensor characteristics and the expected performance are listed, the wide field of applications are mentioned and the required R&D topics are discussed.
•We are proposing thin pixel silicon sensors with 10's of picoseconds time resolution.•Fast charge collection is coupled with internal charge multiplication.•The truly 4-D sensors will revolutionize imaging and particle counting in many applications.
The ELIMED transport and dosimetry beamline for laser-driven ion beams Romano, F.; Schillaci, F.; Cirrone, G.A.P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2016, Letnik:
829
Journal Article
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A growing interest of the scientific community towards multidisciplinary applications of laser-driven beams has led to the development of several projects aiming to demonstrate the possible use of ...these beams for therapeutic purposes. Nevertheless, laser-accelerated particles differ from the conventional beams typically used for multiscipilinary and medical applications, due to the wide energy spread, the angular divergence and the extremely intense pulses. The peculiarities of optically accelerated beams led to develop new strategies and advanced techniques for transport, diagnostics and dosimetry of the accelerated particles. In this framework, the realization of the ELIMED (ELI-Beamlines MEDical and multidisciplinary applications) beamline, developed by INFN-LNS (Catania, Italy) and that will be installed in 2017 as a part of the ELIMAIA beamline at the ELI-Beamlines (Extreme Light Infrastructure Beamlines) facility in Prague, has the aim to investigate the feasibility of using laser-driven ion beams for multidisciplinary applications. In this contribution, an overview of the beamline along with a detailed description of the main transport elements as well as the detectors composing the final section of the beamline will be presented.
The relative biological effectiveness (RBE) concept is commonly used in treatment planning for ion beam therapy. Whether models based on in vitro/in vivo RBE data can be used to predict human ...response to treatments is an open issue. In this work an alternative method, based on an effective radiobiological parameterization directly derived from clinical data, is presented. The method has been applied to the analysis of prostate cancer trials with protons and carbon ions.Prostate cancer trials with proton and carbon ion beams reporting 5 year-local control (LC5) and grade 2 (G2) or higher genitourinary toxicity rates (TOX) were selected from literature to test the method. Treatment simulations were performed on a representative subset of patients to produce dose and linear energy transfer distribution, which were used as explicative physical variables for the radiobiological modelling. Two models were taken into consideration: the microdosimetric kinetic model (MKM) and a linear model (LM). The radiobiological parameters of the LM and MKM were obtained by coupling them with the tumor control probability and normal tissue complication probability models to fit the LC5 and TOX data through likelihood maximization. The model ranking was based on the Akaike information criterion.Results showed large confidence intervals due to the limited variety of available treatment schedules. RBE values, such as RBE = 1.1 for protons in the treated volume, were derived as a by-product of the method, showing a consistency with current approaches. Carbon ion RBE values were also derived, showing lower values than those assumed for the original treatment planning in the target region, whereas higher values were found in the bladder. Most importantly, this work shows the possibility to infer the radiobiological parametrization for proton and carbon ion treatment directly from clinical data.
The Gigatracker, the silicon beam tracker for the NA62 experiment at CERN Federici, L.; Aglieri Rinella, G.; Alvarez Feito, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958
Journal Article
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The Gigatracker is the NA62 beam tracker. It is made of three 63.1mm×29.3mm stations of 300μm×300μm hybrid silicon pixel detectors installed in vacuum (∼10−6mbar). The beam particles, flowing at ...750MHz, are traced in 4-dimensions by mean of time-stamping pixels with a design resolution of 200ps. This performance has to be maintained despite the beam irradiation amounting to a yearly fluence of 2×10141MeVneq∕cm2. The detector material minimization is paramount, as the detector faces the full beam. The station material budget is reduced to 0.5%X0 by using (HEP world first) micro-channels cooling. We will describe the detector design and performances during the NA62 runs.
The Gigatracker detector of the NA62 experiment at CERN SPS Federici, L.; Aglieri Rinella, G.; Alvarez Feito, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
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The NA62 experiment at the CERN SPS is a fixed target experiment designed to measure the branching ratio of the ultra-rare Kaon decay K+→π+νν̄. The experiment uses an high-momentum K+ decay in-flight ...technique to increase the rejection power of the main background: K+→π+π0.
The Gigatracker is a hybrid silicon pixel detector, exposed to a 750 MHz high-energy charged hadron beam, built to give an accurate measurement of K+ momentum and direction together with an high precision measurement of the beam particle arrival time (115 ps RMS resolution per plane). It comprises three stations placed right before the K+ decay region and inserted around two achromats. The detector works in vacuum (∼10−6mbar) at about −10°C.
Each station is made of a 200μm thick silicon sensor readout by 10 TDCPix, custom 100μm thick ASICs, and cooled by an innovative double circuit silicon micro-channel cooling system. All these parts are designed to minimize the total material budget which, in the final detector, amounts to less than 1.5% X0 for the three stations.
In order to sustain the high rate of incoming particles, each TDCPix, operating in a self triggered mode, is equipped with four 3.2 Gb/s serializers sending data to the detector DAQ system based on a read-out card per TDCPix chip sending trigger-matched hits to 6 PC servers. I will describe the whole detector and present some of the results from data collected during the 2016 NA62 runs.
A new hadron-therapy facility implementing an active beam scanning technique has been developed at the Italian National Center of Oncological Hadron-therapy (CNAO). This paper presents the design and ...the characterization of the beam monitor detectors developed for the on-line monitoring and control of the dose delivered during a treatment at CNAO. The detectors are based on five parallel-plate transmission ionization chambers with either a single large electrode or electrodes segmented in 128 strips (strip chambers) and 32×32pixels (pixel chamber). The detectors are arranged in two independent boxes with an active area larger than 200×200mm2 and a total water equivalent thickness along the beam path of about 0.9mm. A custom front-end chip with 64 channels converts the integrated ionization channels without dead-time.
The detectors were tested at the clinical proton beam facility of the Paul Scherrer Institut (PSI) which implements a spot scanning technique, each spot being characterized by a predefined number of protons delivered with a pencil beam in a specified point of the irradiation field. The short-term instability was measured by delivering several identical spots in a time interval of few tenths of seconds and is found to be lower than 0.3%. The non-uniformity, measured by delivering sequences of spots in different points of the detector surface, results to be lower than 1% in the single electrode chambers and lower than 1.5% in the strip and pixel chambers, reducing to less than 0.5% and 1% in the restricted 100×100mm2 central area of the detector.
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