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- dos Santos Matias, Lucilio, et al.
(författare)
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Characterization of the radiation field surrounding the Leksell Gamma Knife® and shielding applications
- 2023
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Ingår i: Applied Radiation and Isotopes. - 0969-8043 .- 1872-9800. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to improve the characterization and modeling of the radiation field surrounding the Leksell Gamma Knife®-PerfexionTM. The improved characterization of the radiation field enables more accurate shielding calculations to be performed for the areas adjacent to the treatment room. With the aid of a high-purity germanium detector and a satellite dose rate meter, ?-ray spectra and ambient dose equivalent H*(10) data were acquired at various locations in the field of a Leksell Gamma Knife unit in a treatment room at Karolinska University Hospital, Sweden. These measurements were used to validate the results of the PEGASOS Monte Carlo simulation system with a PENELOPE kernel. The levels of the radiation that passes through the shielding of the machine (leakage radiation) are shown to be much lower than what is suggested by various bodies, e.g. the National Council on Radiation Protection and Measurements, to be used when calculating radiation shielding barriers. The results clearly indicate that Monte Carlo simulations may be used in structural shielding design calculations for γ? rays from the Leksell Gamma Knife.
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- dos Santos Matias, Lucílio, 1980-, et al.
(författare)
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Drawbacks of the current NCRP models on shielding calculations : Development of a new methodology for the Gamma Knife®
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Most practical guidelines for design of shielding against photon radiotherapy equipment may be retrieved from the National Council on Radiation Protection and Measurements (NCRP) report 151. The NCRP report No. 151 formalism describes structural shielding design techniques for megavoltage x- and gamma-ray radiotherapy facilities with the aim to limit radiation exposures to members of the public, employees, and the environment to an acceptable level. The implemetaion of NCRP report No. 151 recommendations may be straightforward for linear accelerators and conventional Co-60 machines which have singular source of radiation in contrast to the Leksell Gamma Knife, which has a complex multisource configuration. To harness the full potential of the NCRP 151 methodology, complementary transmission measurements may be required. In the NCRP report No. 151 the primary barriers are designed to attenuate photons emanating directly from the treatment unit while secondary barriers are calculated to shield radiation leakage and scattered photons by the patient and objects inside the treatment room. Here it is assumed that a primary radiation barrier should at the same time shield against secondary radiation. In this work the gamma-ray spectra in the vicinity of the Elekta Leksell Gamma Knife-Perfexion were acquired using a High Purity Germanium detector. It has been observed that the proportion of high energetic photons is lower in comparison with photons with low energy. This corroborates with the fact that the Leksell Gamma Knife has been designed in order to prevent any primary radiation from exiting the unit without impinging on an internal interceptor shield during all states of the machine. Therefore, the need to adapt the NCRP methodology for the Gamma Knife appeared to be justified.
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| 4. |
- Erni, W., et al.
(författare)
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Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
- 2013
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
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Tidskriftsartikel (refereegranskat)abstract
- This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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- Marcks von Wurtemberg, Klas, et al.
(författare)
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The response of lead-tungstate scintillators (PWO) to photons with energies in the range 13 MeV-64 MeV
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 679, s. 36-43
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Tidskriftsartikel (refereegranskat)abstract
- The response of a matrix of 25 lead tungstate (PWO) scintillator detectors, operated at -25 degrees C, to photons in the range 13 MeV-64 MeV has been measured at the tagged-photon facility at MAX-lab, Lund. The tapered PWO crystals, each with a length of 200 mm and a cross-section of 24.4 x 24.4 mm(2) in the front end, read out by 19 mm photomultiplier tubes, were arranged in a 5 x 5 matrix. The response was measured for photons directed towards the centre of the central crystal as well as for photons directed towards the corner of the central crystal, where four crystals meet. The obtained energy resolution surpasses what has been published so far and is close to the limit given by Poisson statistics and escaped energy. For photons directed towards the centre(corner) of the central crystal the relative energy resolution, defined as (FWHM/2.35)/E-gamma, decreases from 7.3%(11.0%) at E-gamma = 13 MeV to 3.3%(3.6%) at E-gamma = 64 MeV. The reconstructed point of impact of a photon in this energy range is determined with an uncertainty (one standard deviation) of 7.3 +/- 0.1 mm.
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