Proton imaging can be seen as a powerful technique for on-line monitoring of ion range during carbon ion therapy irradiation. The protons detection technique uses, as three-dimensional tracking ...system, a set of CMOS sensor planes. A simulation toolkit based on GEANT4 and ROOT is presented including detector response and reconstruction algorithm.
Time resolution measurements were performed using four digital timing algorithms and a pair of truncated-cone shaped, 38-mm diameter LaBr(Ce) fast-timing scintillator detectors. The best resolution ...FWHM=143(3) ps was found for transitions from a 60Co source when fitting the rising part of sampled waveforms with a cubic polynomial and applying a leading-edge threshold. An average-pulse autocovariance function performed slightly worse 155(3) ps, but was found to be better than digital constant-fraction 178(4) ps and leading-edge 177(4) ps algorithms. Use of a 152Eu source allowed the performance of the four algorithms to be tested across a range of -ray energies with the LaBr(Ce) detectors. Here the autocovariance algorithm performed best. Changing the sampling speed showed minimal degradation in the time resolution at 20 GS/s, though at 4 GS/s the resolutions were 30–60% worse. These results show that at sampling speeds of 20 or 40 GS/s the time resolutions obtained are close to those reported for analogue pulse-processing electronics. Compared to other works, using slower sampling speeds but higher vertical resolution, slightly worse performance was obtained.
Diamond is a very promising material for various applications, and understanding its basic properties is key for the development of future devices. In particular, the low-field mobility of holes has ...never been measured below ∼80 K in ultra-pure diamond. In order to measure this mobility, we developed an innovative Time of Flight electron Beam Induced Current (ToF-eBIC) technique. A 1 ns pulsed electron beam was made to impact the diamond semiconductor, inducing charge carrier creation and motion through the 546 µm thick bulk diamond, under the influence of an applied electric field. The resulting signal was analysed using the transient time technique. Thus, the velocity of electrons and holes was assessed as a function of the temperature from 13 to 300 K and as a function of the electric field with values ranging from 1.5 to 9200 V/cm. A low-field mobility value of 1.03 ± 0.05 × 10 6 cm 2 V −1 s −1 was measured for holes at 13 K, demonstrating that diamond is a suitable material to transport charge carriers in a ballistic regime at a scale of ten micrometers.
Le diamant est un matériau très prometteur pour diverses applications, et la compréhension de ses propriétés de base est essentielle pour le développement de futurs dispositifs. En particulier, la mobilité des trous à bas champ n'a jamais été mesurée en dessous de ∼80 K dans le diamant ultra-pur. Afin de mesurer cette mobilité, nous avons développé une technique innovante de courant induit par faisceau d'électrons à temps de vol (ToF-eBIC). Un faisceau d'électrons pulsé de 1 ns a été envoyé sur le semi-conducteur en diamant, induisant la création et le déplacement de porteurs de charge à travers le diamant massif de 546 µm d'épaisseur, sous l'influence d'un champ électrique appliqué. Le signal résultant a été analysé à l'aide de la technique du temps transitoire. Ainsi, la vitesse des électrons et des trous a été évaluée en fonction de la température de 13 à 300 K et en fonction du champ électrique avec des valeurs allant de 1,5 à 9200 V/cm. Une mobilité à faible champ de 1,03 ± 0,05 × 10 6 cm 2 V -1 s -1 a été mesurée pour les trous à 13 K, démontrant que le diamant est un matériau approprié pour transporter des porteurs de charge dans un régime balistique à une échelle de dix micromètres.
In an experiment with relativistic highly charged ions (β=v/c=0.56) channeled through a silicon crystal the resonant coherent excitation of the 2s1/2-2p3/2 transition in 191 MeV/u Li-like uranium ...ions was observed. The resonant condition was identified by measuring the x-ray emission as a function of the ion incidence angle with respect to the 110 crystal axis in the (220) plane. The position and the width of the resonance where determined from the dependence of the x-ray yield from the 2p3/2-2s1/2 decay on the angular orientation of the crystal.
A new kind of positron sources for future linear colliders, where the converter is an aligned tungsten crystal, oriented on the 〈111〉-axis, has been studied at CERN in the WA103 experiment with ...tertiary electron beams from the SPS. In such sources the photons resulting from channeling radiation and coherent bremsstrahlung create the e+e− pairs.
Electron beams, of 6 and 10GeV, were impinging on different kinds of targets: a 4mm thick crystal, a 8mm thick crystal and a compound target made of 4mm crystal followed by 4mm amorphous disk. An amorphous tungsten target 20mm thick was also used for the sake of comparison with the 8mm crystal and to check the ability of the detection system to provide the correct track reconstruction. The charged particles coming out from the target were detected in a drift chamber immersed partially in a magnetic field. The reconstruction of the particle trajectories provided the energy and angular spectrum of the positrons in a rather wide energy range (up to 150MeV) and angular domain (up to 30°). The experimental approach presented in this article provides a full description of this kind of source. A presentation of the measured positron distribution in momentum space (longitudinal versus transverse) is given to allow an easy determination of the available yield for a given momentum acceptance. Results on photons, measured downstream of the positron detector, are also presented. A significant enhancement of photon and positron production is clearly observed. This enhancement, for a 10GeV incident beam, is of 4 for the 4mm thick crystal and larger than 2 for the 8mm thick crystal. Another important result concerns the validation of the simulations for the crystals, for which a quite good agreement was met between the simulations and the experiment, for positrons as well as for photons. These results are presented after a short presentation of the experimental setup and of the track reconstruction procedure.
A thin germanium crystal has been irradiated at GANIL by Pb beams of 29
MeV/A (charge state
Q
in
=
56 and 72) and of 5.6
MeV/A (
Q
in
=
28). The induced ion emission from the sample entrance surface ...was studied, impact per impact, as a function of
Q
in, velocity
v
in
and energy loss Δ
E in the crystal. The Pb ions transmitted through the crystal were analyzed in charge (
Q
out) and energy using the SPEG spectrometer. The emitted ionized species were detected and analyzed in mass by a time-Of-flight multianode detector (LAG). Channeling was used to select peculiar Δ
E values in Ge and hence peculiar Pb ion trajectories close to the emitting entrance surface. The experiment was performed in standard vacuum. No Ge emission was found. The dominating emitted species are H
+ and hydrocarbon ions originating from the contamination layer on top of the crystal. The mean value 〈
M〉 of the number of detected species per incoming Pb ion (multiplicity) varies as (
Q
in/
v
in
)
p
, with
p values in agreement with previous results. We have clearly observed an influence of the energy deposition Δ
E in Ge on the emission from the top contamination layer. When selecting increasing values of Δ
E, we observed a rather slow increase of 〈
M〉. On the contrary, the probabilities of high multiplicity values, which are essentially connected to fragmentation after emission, strongly increase with Δ
E.
In this first inaugural joint ESTRO‐AAPM session we will attempt to provide some answers to the problems encountered in the clinical application of particle therapy.
Indeed the main advantage is that ...the physical properties of ion beams offer high ballistic accuracy for tightly conformal irradiation of the tumour volume, with excellent sparing of surrounding healthy tissue and critical organs, This also its Achilles' heel calling for an increasing role of imaging to ensure safe application of the intended dose to the targeted area during the entire course of fractionated therapy.
We have three distinguished speakers addressing possible solutions.
Katia Parodi (Ludwig Maximilians University, Munich, Germany)
To date, Positron Emission Tomography (PET) is the only technique which has been already clinically investigated for in‐vivo visualization of the beam range during or shortly after ion beam delivery. The method exploits the transient amount of β2‐activity induced in nuclear interactions between the primary beam and the irradiated tissue, depending on the ion beam species, the tissue elemental composition and physiological properties (in terms of biological clearance), as well as the time course of irradiation and imaging. This contribution will review initial results, ongoing methodological developments and remaining challenges related to the clinical usage of viable but often suboptimal instrumentation and workflows of PET‐based treatment verification. Moreover, it will present and discuss promising new detector developments towards next‐generation dedicated PET scanners relying on full‐ring or dual‐head designs for in‐beam quasi real‐time imaging.
Denis Dauvergne (Institut de Physique Nucleaire de Lyon, Lyon, France) Prompt gamma radiation monitoring of hadron therapy presents the advantage of real time capability to measure the ion range. Both simulations and experiments show that millimetric verification of the range can be achieved at the pencil beam scale for active proton beam delivery in homogenous targets. The development of gamma cameras, that has been studied by several groups worldwide over the last years, now reaches – for some of them – the stage of being applicable in clinical conditions, with real size prototypes and count rate capability matching the therapeutic beam intensities. We will review the different concepts of gamma cameras, the advantages and limitations of this method, and the main challenges that should still be overcome before the widespread of prompt gamma quality assurance for proton and hadrontherapy.
Jon Kruse (Mayo Clinic, Rochester, MN, USA)
Treatment simulation images for proton therapy are used to determine proton stopping power and range in the patient. This talk will discuss the careful control of CT numbers and conversion of CT number to stopping power required in proton therapy. Imaging for treatment guidance of proton therapy also presents unique challenges which will be addressed. Among them are the enhanced relationship between internal anatomy changes and dosimetry, the need for imaging to support adaptive planning protocols, and high operational efficiency.
Learning Objectives:
1.To learn about the possibilities of using activation products to determine the range of particle beams in a patient treatment setting
2.To be informed on an alternative methodology using prompt gamma detectors
3.To understand the impact of the accuracy of the knowledge of the patient information with respect to the delivered treatment.
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