[Show abstract][Hide abstract] ABSTRACT: The Monte Carlo particle transport code SHIELD-HIT12A is designed to simulate therapeutic beams for cancer radiotherapy with fast ions. SHIELD-HIT12A allows creation of antiproton beam kernels for the treatment planning system TRiP98, but first it must be benchmarked against experimental data. An experimental depth dose curve obtained by the AD-4/ACE collaboration was compared with an earlier version of SHIELD-HIT, but since then inelastic annihilation cross sections for antiprotons have been updated and a more detailed geometric model of the AD-4/ACE experiment was applied.
Full-text · Article · Mar 2015 · Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
[Show abstract][Hide abstract] ABSTRACT: The Aarhus positron beam line is utilised to measure the positronium formation fraction from porous silica thin films created by the Glancing Angle Deposition technique. The highest formation fraction found from these studies in a backscattering geometry is (57.7 +/- 1.0)% in good agreement with other measurements. In transmission mode, the maximum positronium output is found to be (12.5 +/- 0.5)%. These are the first measurements of positronium formation in transmission of a porous silica thin film, a starting point for future attempts to optimise the positronium formation in transmission.
No preview · Article · May 2014 · The European Physical Journal D
[Show abstract][Hide abstract] ABSTRACT: We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron. With the present setup it is possible to control the separation of the foils on a μm scale and hence measure interference effects caused by the macroscopic dimensions of the formation length. Several theoretical groups have predicted this effect using different methods. Our observations have a preference for the modified theory by Blankenbecler but disagree with the results of Baier and Katkov.
No preview · Article · Feb 2012 · Physical Review Letters
[Show abstract][Hide abstract] ABSTRACT: Experimental and theoretical progress in the field of antiproton-impact-induced ionization of atoms and molecules is reviewed. We describe the techniques used to measure ionization cross sections and give an overview of the experimental results supplemented by tables of all existing data. An attempt is made to discuss the multitude of theoretical approaches and models of the last 10–15 years in terms of a few categories which characterize their level of sophistication. This sets the stage for in-depth comparisons of experimental and theoretical results and a critical evaluation of the present status of our understanding of antiproton impact ionization. The related issues of energy loss measurements and antiproton therapy are briefly described and directions for possible future work are pointed out as well.
No preview · Article · May 2011 · Journal of Physics B Atomic Molecular and Optical Physics
[Show abstract][Hide abstract] ABSTRACT: During the last two decades, we have obtained experimental data for a broad impact energy range (3 keV – 20 MeV) of the total cross sections for single and multiple ionization in collisions between antiprotons and a number of atoms and molecules, as well as cross sections for fragmentation of those molecules. In this paper we discuss the experimental progress which was necessary for this achievement and present and discuss some of the data obtained.
No preview · Article · Dec 2009 · Journal of Physics Conference Series
[Show abstract][Hide abstract] ABSTRACT: Radiotherapy of cancer carries a perceived risk of inducing secondary cancer and other damage due to dose delivered to normal tissue. While expectedly small, this risk must be carefully analysed for all modalities. Especially in the use of exotic particles like pions and antiprotons, which annihilate and produce a mixed radiation field when interacting with normal matter nuclei, the biological effective dose far out of field needs to be considered in evaluating this approach. We describe first biological measurements to address the concern that medium and long range annihilation products may produce a significant background dose and reverse any benefits of higher biological dose in the target area.
Using the Antiproton Decelerator (AD) at CERN (Conseil Européen pour la Recherche Nucléaire) we irradiated V-79 Chinese Hamster cells embedded in gelatine using an antiproton beam with fluence ranging from 4.5 x 10(8) to 4.5 x 10(9) particles, and evaluated the biological effect on cells located distal to the Bragg peak using clonogenic survival and the COMET assay.
Both methods show a substantial biological effect on the cells in the entrance channel and the Bragg Peak area, but any damage is reduced to levels well below the effect in the entrance channel 15 mm distal to the Bragg peak for even the highest particle fluence used.
The annihilation radiation generated by antiprotons stopping in biological targets causes an increase of the penumbra of the beam but the effect rapidly decreases with distance from the target volume. No major increase in the biological effect is found in the far field outside of the primary beam.
No preview · Article · Dec 2009 · International Journal of Radiation Biology
[Show abstract][Hide abstract] ABSTRACT: We have measured the depth-dose curve of 126 MeV antiprotons in a water phantom using ionization chambers. Since the antiproton beam provided by CERN has a pulsed structure and possibly carries a high-LET component from the antiproton annihilation, it is necessary to correct the acquired charge for ion recombination effects. The results are compared with Monte Carlo calculations and were found to be in good agreement. Based on this agreement we calculate the antiproton depth-dose curve for antiprotons and compare it with that for protons and find a doubling of the physical dose in the peak region for antiprotons.
Full-text · Article · Mar 2008 · Physics in Medicine and Biology
[Show abstract][Hide abstract] ABSTRACT: Antiprotons are interesting as a possible future modality in radiation therapy for the following reasons: When fast antiprotons penetrate matter, protons and antiprotons have near identical stopping powers and exhibit equal radiobiology well before the Bragg-peak. But when the antiprotons come to rest at the Bragg-peak, they annihilate, releasing almost 2 GeV per antiproton-proton annihilation. Most of this energy is carried away by energetic pions, but the Bragg-peak of the antiprotons is still locally augmented with approximately 20-30 MeV per antiproton. Apart from the gain in physical dose, an increased relative biological effect also has been observed, which can be explained by the fact that some of the secondary particles from the antiproton annihilation exhibit high-LET properties. Finally, the weakly interacting energetic pions, which are leaving the target volume, may provide a real time feedback on the exact location of the annihilation peak. We have performed dosimetry experiments and investigated the radiobiological properties using the antiproton beam available at CERN, Geneva. Dosimetry experiments were carried out with ionization chambers, alanine pellets and radiochromic film. Radiobiological experiments were done with V79 WNRE Chinese hamster cells. The radiobiological experiments were repeated with protons and carbon ions at TRIUMF and GSI, respectively, for comparison. Several Monte Carlo particle transport codes were investigated and compared with our experimental data obtained at CERN. The code that matched our data best was used to generate a set of depth dose data at several energies, including secondary particle-energy spectra. This can be used as base data for a treatment planning software such as TRiP. Our findings from the CERN experiments indicate that the biological effect of antiprotons in the plateau region may be reduced by a factor of 4 for the same biological target dose in a spread-out Bragg-peak, when comparing with protons. The extension of TRiP to handle antiproton beams is currently in progress. This will enable us to perform planning studies, where the potential clinical consequences can be examined, and compared to those of other beam modalities such as protons, carbon ions, or IMRT photons.
Full-text · Article · Feb 2008 · Radiotherapy and Oncology
[Show abstract][Hide abstract] ABSTRACT: Radiotherapy is one of the most important means we have for the treatment of localised tumours. It is therefore essential to optimize the technique, and a lot of effort goes into this endeavour. Since the proposal by Wilson in 1946 [R.R. Wilson, Radiology use of fast protons, Radiology 47 (1946) 487.] that proton beams might be better than photon beams at inactivating cancer cells, hadron therapy has been developed in parallel with photon therapy and a substantial knowledge has been gained on the effects of pions, protons and heavy ions (mostly carbon ions). Here we discuss the recent measurements by the CERN ACE collaboration of the biological effects of antiprotons, and argue that these particles very likely are the optimal agents for radiotherapy.
No preview · Article · Feb 2008 · Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
[Show abstract][Hide abstract] ABSTRACT: Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first ever measurements of the biological effectiveness of antiprotons.
V79 cells were suspended in a semi-solid matrix and irradiated with 46.7MeV antiprotons, 48MeV protons, or (60)Co gamma-rays. Clonogenic survival was determined as a function of depth along the particle beams. Dose and particle fluence response relationships were constructed from data in the plateau and Bragg peak regions of the beams and used to assess the biological effectiveness.
Due to uncertainties in antiproton dosimetry we defined a new term, called the biologically effective dose ratio (BEDR), which compares the response in a minimally spread out Bragg peak (SOBP) to that in the plateau as a function of particle fluence. This value was approximately 3.75 times larger for antiprotons than for protons. This increase arises due to the increased dose deposited in the Bragg peak by annihilation and because this dose has a higher relative biological effectiveness (RBE).
We have produced the first measurements of the biological consequences of antiproton irradiation. These data substantiate theoretical predictions of the biological effects of antiproton annihilation within the Bragg peak, and suggest antiprotons warrant further investigation.
Full-text · Article · Jan 2007 · Radiotherapy and Oncology
[Show abstract][Hide abstract] ABSTRACT: In the light of recent progress in the study of the biological potential of antiproton tumour treatment it is important to be able to characterize the neutron intensity arising from antiproton annihilation using simple, compact and reliable detectors. The intensity of fast neutrons from antiproton annihilation on polystyrene has been measured with bubble detectors and a multiplicity has been derived as well as an estimated neutron equivalent dose. Additionally the sensitivity of bubble detectors towards protons was measured.
Mixed radiation field
Full-text · Article · Sep 2006 · Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
[Show abstract][Hide abstract] ABSTRACT: Abstract. Starting in 2003 the AD-4/ACE collaboration has studied the biological effects of
antiprotons annihilating in a human tissue like material on live V-79 Chinese Hamster cells. The
main goal of the work is to prove the efficacy of antiprotons for cancer therapy. In this report we
discuss a critical point to be considered carefully for all particle beam radiation therapies,
namely the loss of primary particles from the beam on the way to a tumor seated some distance
below the surface.
Full-text · Article · Oct 2005 · AIP Conference Proceedings
[Show abstract][Hide abstract] ABSTRACT: A merged-beam set-up for absolute measurements of photoionization cross-sections of ions is described. The facility is capable of recording cross-sections as low as 10−19 cm2 and has been used to study a large number of singly- and multiply-charged, atomic and molecular, positive and negative ions. It is based on a synchrotron radiation beam line fitted with an undulator at the storage ring ASTRID and a low-energy (∼2 keV) ion beam line. Photons in the energy range 15–200 eV are merged co-linearly with the target ions over a distance of 50 cm, and the absolute photoionization cross-section is determined from the resulting photoion yield with a typical accuracy of 10%. Different types of ion sources are available, thus permitting a large number of positive and negative, atomic and molecular, singly- and multiply-charged ions to be investigated. Emphasis is put on accurate determination of the absolute cross-sections, requiring calibration of photodiode and particle detectors together with measurements of the photon–ion overlap.
No preview · Article · Jun 2005 · Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
[Show abstract][Hide abstract] ABSTRACT: A new experiment, AD-4/ACE (antiproton cell experiment), has been approved by the CERN Research Board. The experiment is scheduled to begin taking data in June and continue through the 2003 run cycle. The experiment is designed to determine whether or not the densely ionizing particles emanating from the annihilation of antiprotons produce an increase in “biological dose” in the vicinity of the narrow Bragg peak for antiprotons compared to protons. This experiment is the first direct measurement of the biological effects of antiproton annihilation. The background, description, and status of the experiment are given.
Full-text · Article · Jul 2004 · Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
[Show abstract][Hide abstract] ABSTRACT: Summary Our experimental proposal to study the biological effect of antiprotons was approved by the SPSC in January of 2003 for beam time in the run cycle of 2003. So far during the summer of 2003 AD-4 has received 10 shifts of beam in three independent blocks of time. These shifts were used to perform an initial experiment to establish the correct dose range for meaningful biological exposures, to develop and enhance our dosimetry capabilities, and to perform the first full biological sample irradiation. This document describes these experiments in detail and highlights the problems, challenges, and achievements of our collaboration during this time. We also comment on the upcoming final run time for this year and present an outlook for the future, detailing a program for a possible continuation in 2004.