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  • 1.
    Dangtip, Somsak
    et al.
    Department of Neutron Research, Uppsala University, Sweden.
    Söderberg, Jonas
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Description of the Medley Code: Monte Carlo Simulation of the Medley Setup1998Report (Other academic)
    Abstract [en]

    Neutron-induced charged-particle production, i.e., reactions like (n,xp), (n,xd), (n,xt), (n,x3He) and (n,xa), yields a large - and relatively poorly known - contribution to the dose delivered in fast-neutron cancer therapy. At the The Svedberg Laboratory (TSL) in Uppsala, a project is underway to measure these cross sections with a precision required for clinical use.

    For this purpose, an experimental facility, MEDLEY, is under commissioning. It consists of eight detector telescopes, each being a Si-Si-CsI detector combination. This general design has been selected because it provides reasonable performance over the very wide dynamic range required to detect particles ranging from 5 MeV a particles to 100 MeV protons. A general problem in this kind of experiments is to characterize the response of the detection system. The MEDLEY code has been developed for this purpose.

    Experimental studies of these kinds of charged-particle reactions show specific features. Some of these need to be optimized by means of, for instance, computer codes, prior to the measurement if good data are to be achieved.

    Basically, charged particles loose energy along their paths by interactions with the electrons of the material. Particles with low energy or with high specific energy loss are easily absorbed. Systems, which use thick charged-particle production targets to gain desirable count rate, can then detect only charged particles with enough energy to escape the target. Thus, using a thick target results in a degraded energy resolution, and particle losses. Thin targets are required to provide better resolution, but at the cost of low count rates.

    Registration of the entire energy of the particles reaching the detection system is also an ultimate goal. However, charged particles can interact with detection materials via nuclear reactions, which could result in other species of particles. From the detection point of view, the primary particles are lost and replaced by new types of particles, which may behave differently from their predecessors.

    It is well known that charged particles traveling in a medium are deflected by many small-angle scatterings. This so-called multiple scattering can be described with a statistical distribution. The fluctuations in energy loss per step, called energy-loss straggling, are modeled in the same way, i.e., assuming a statistical behavior.

    To get an acceptable neutron beam intensity, a rather thick neutron production target (2-8 mm) is required. This causes an energy spread of the incident neutron beam. In our case, the spread after a 4 mm thick 7Li target for neutron production is of the order of about 2 MeV.

    To analyze the data and determine the true double-differential cross sections, the above mentioned effects have to be taken into consideration. We have therefore developed a Monte Carlo code, MEDLEY, in FORTRAN language, to simulate the experimental setup taking all relevant physical characteristics into account. In the MEDLEY code, particles, chosen from a given distribution, are followed through the detection system. The particle distribution is obtained by applying a stripping method to the measured spectrum supplied by a user. When the result from the MEDLEY code is in good agreement with the experimental data, the true double-differential cross sections is obtained. If needed, the correction procedure can be iterated. This iteration is performed until the above condition is satisfied.

    This report presents the features included in the code, and some results. We compare ourresults with those from others where available.

  • 2.
    Grindborg, J.-E.
    et al.
    Swedish Radiation Protection Authority, Stockholm, Sweden.
    Lillhok, J.E.
    Lillhök, J.E., Swedish Radiation Protection Authority, Stockholm, Sweden.
    Lindborg, L.
    Swedish Radiation Protection Authority, Stockholm, Sweden.
    Gudowska, I.
    Medical Radiation Physics, Karolinska Institutet, Stockholm University, Stockholm, Sweden.
    Söderberg, Jonas
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiation Physics .
    Carlsson, Görel
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Thematic Studies.
    Nikjoo, H.
    NASA Johnson Space Center, Houston, TX, United States.
    Nanodosimetric measurements and calculations in a neutron therapy beam2007In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 126, no 1-4, p. 463-466Article in journal (Refereed)
    Abstract [en]

    A comparison of calculated and measured values of the dose mean lineal energy (yD) for the former neutron therapy beam at Louvain-la-Neuve is reported. The measurements were made with wall-less tissue-equivalent proportional counters using the variance-covariance method and simulating spheres with diameters between 10 nm and 15 µm. The calculated yD-values were obtained from simulated energy distributions of neutrons and charged particles inside an A-150 phantom and from published yD-values for mono-energetic ions. The energy distributions of charged particles up to oxygen were determined with the SHIELD-HIT code using an MCNPX simulated neutron spectrum as an input. The mono-energetic ion yD-values in the range 3-100 nm were taken from track-structure simulations in water vapour done with PITS/KURBUC. The large influence on the dose mean lineal energy from the light ion (A > 4) absorbed dose fraction, may explain an observed difference between experiment and calculation. The latter being larger than earlier reported result. Below 50 nm, the experimental values increase while the calculated decrease. © The Author 2007. Published by Oxford University Press. All rights reserved.

  • 3. Lillhök, Jan Erik
    et al.
    Grindborg, Jan-Erik
    Lindborg, Lennart
    Gudowska, Irena
    Alm-Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Söderberg, Jonas
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics.
    Kopec, M
    Medin, Joakim
    Nanodosimetry in a clinical neutron therapy beam using the variance-covariance method and Monte Carlo simulations2007In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 52, no 16, p. 4953-4966Article in journal (Refereed)
    Abstract [en]

    Nanodosimetric single-event distributions or their mean values may contribute to a better understanding of how radiation induced biological damages are produced. They may also provide means for radiation quality characterization in therapy beams. Experimental nanodosimetry is however technically challenging and Monte Carlo simulations are valuable as a complementary tool for such investigations. The dose-mean lineal energy was determined in a therapeutic p(65)+Be neutron beam and in a 60Co γ beam using low-pressure gas detectors and the variance-covariance method. The neutron beam was simulated using the condensed history Monte Carlo codes MCNPX and SHIELD-HIT. The dose-mean lineal energy was calculated using the simulated dose and fluence spectra together with published data from track-structure simulations. A comparison between simulated and measured results revealed some systematic differences and different dependencies on the simulated object size. The results show that both experimental and theoretical approaches are needed for an accurate dosimetry in the nanometer region. In line with previously reported results, the dose-mean lineal energy determined at 10 nm was shown to be related to clinical RBE values in the neutron beam and in a simulated 175 MeV proton beam as well. © 2007 IOP Publishing Ltd.

  • 4. Somsak, Dangtip
    et al.
    Atac, A
    Bergenwall, B
    Blomgren, J
    Elmgren, K
    Johansson, C
    Klug, J
    Olsson, Nils
    Alm Carlsson, Gudrun
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Söderberg, Jonas
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Facility for measurements of nuclear cross sections for fast neutron cancer therapy2000In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 452, no 3, p. 484-504Article in journal (Refereed)
    Abstract [en]

    A facility for measurements of neutron-induced double-differential light-ion production cross-sections, for application within, e.g., fast neutron cancer therapy, is described. The central detection elements are three-detector telescopes consisting of two silicon detectors and a CsI crystal. Use of ?E-?E-E techniques allows good particle identification for p, d, t, 3He and alpha particles over an energy range from a few MeV up to 100 MeV. Active plastic scintillator collimators are used to define the telescope solid angle. Measurements can be performed using up to eight telescopes at 20░ intervals simultaneously, thus covering a wide angular range. The performance of the equipment is illustrated using experimental data taken with a carbon target at En = 95 MeV. Distortions of the measured charged-particle spectra due to energy and particle losses in the target are corrected using a newly developed computer code. Results from such correction calculations are presented.

  • 5.
    Stenström, Mats
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Olander, Birger
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Söderberg, Jonas
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Sandborg, Michael
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Absorbed dose aspects on in vivo microtomography on small experimental animals2001In: Journal of Bone and Mineral Research, ISSN 0884-0431, E-ISSN 1523-4681Article in journal (Refereed)
  • 6.
    Söderberg, Jonas
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Dosimetry and radiation quality in fast-neutron radiation therapy: A study of radiation quality and basic dosimetric properties of fast-neutrons for external beam radiotherapy and problems associated with corrections of measured charged particle cross-sections2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The dosimetric properties of fast-neutron beams with energies ≤80 MeV were explored using Monte Carlo techniques. Taking into account transport of all relevant types of released charged particles (electrons, protons, deuterons, tritons, 3He and α particles) pencil-beam dose distributions were derived and used to calculate absorbed dose distributions. Broad-beam depth doses in phantoms of different materials were calculated and compared and the scaling factors required for converting absorbed dose in one material to absorbed dose in another derived. The scaling factors were in good agreement with available published data and show that water is a good substitute for soft tissue even at neutron energies as high as 80 MeV. The inherent penumbra and the fraction of absorbed dose due to photon interactions were also studied, and found to be consistent with measured values reported in the literature.

    Treatment planning in fast-neutron therapy is commonly performed using dose calculation algorithms designed for photon beam therapy. When applied to neutron beams, these algorithms have limitations arising from the physical models used. Monte Carlo derived neutron pencil-beam kernels were parameterized and implemented in the photon dose calculation algorithms of the TMS (MDS Nordion) treatment planning system. It was shown that these algorithms yield good results in homogeneous water media. However, the method used to calculate heterogeneity corrections in the photon dose calculation algorithm did not yield correct results for neutron beams in heterogeneous media.

    To achieve results with adequate accuracy using Monte Carlo simulations, fundamental cross-section data are needed. Neutron cross-sections are still not sufficiently well known. At the The Svedberg Laboratory in Uppsala, Sweden, an experimental facility has been designed to measure neutron-induced charged-particle production cross-sections for (n,xp), (n,xd), (n,xt), (n,x3He) and (n,xα) reactions at neutron energies up to 100 MeV. Depending on neutron energy, these generated particles account for up to 90% of the absorbed dose. In experimental determination of the cross-sections, measured data have to be corrected for the energies lost by the charged particles before leaving the target in which they were generated. To correct for the energy-losses, a computational code (CRAWL) was developed. It uses a stripping method. With the limitation of reduced energy resolution, spectra derived using CRAWL compares well with those derived using other methods.

    In fast-neutron therapy, the relative biological effectiveness (RBE) varies from 1.5 to 5, depending on neutron energy, dose level and biological end-point. LET and other physical quantities, developed within the field of microdosimetry over the past couple of decades, have been used to describe RBE variations between different fast-neutron beams as well as within a neutron irradiated body. In this work, a Monte Carlo code (SHIELD-HIT) capable of transporting all charged particles contributing to absorbed dose, was used to calculate energy-differential charged particle spectra. Using these spectra, values of the RBE related quantities LD, γD, γ* and R were derived and studied as function of neutron energy, phantom material and position in a phantom. Reasonable agreement with measured data in the literature was found and indicates that the quantities may be used to predict RBE variations in an arbitrary fast-neutron beam.

    List of papers
    1. Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods
    Open this publication in new window or tab >>Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods
    2002 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 195, no 3-4, p. 426-434Article in journal (Refereed) Published
    Abstract [en]

    The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x3He) and (n, xα) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.

    Keywords
    Neutron, Cross-section, Charged particle, Energy-loss corrections
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14359 (URN)10.1016/S0168-583X(02)01090-X (DOI)000178915500023 ()
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2017-12-13
    2. Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study
    Open this publication in new window or tab >>Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study
    2000 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 45, no 10, p. 2987-3007Article in journal (Refereed) Published
    Abstract [en]

    Neutron pencil-beam absorbed dose distributions in phantoms of bone, ICRU soft tissue, muscle, adipose and the tissue substitutes water, A-150 (plastic) and PMMA (acrylic) have been calculated using the Monte Carlo code FLUKA in the energy range 0.5 to 80 MeV. For neutrons of energies ≤20 MeV, the results were compared to those obtained using the Monte Carlo code MCNP4B. Broad-beam depth doses and lateral dose distributions were derived. Broad-beam dose distributions in various materials were compared using two kinds of scaling factor: a depth-scaling factor and a dose-scaling factor. Build-up factors due to scattered neutrons and photons were derived and the appropriate choice of phantom material for determining dose distributions in soft tissue examined. Water was found to be a good substitute for soft tissue even at neutron energies as high as 80 MeV. The relative absorbed doses due to photons ranged from 2% to 15% for neutron energies 10-80 MeV depending on phantom material and depth. For neutron energies below 10 MeV the depth dose distributions derived with MCNP4B and FLUKA differed significantly, the difference being probably due to the use of multigroup transport of low energy (<19.6 MeV) neutrons in FLUKA. Agreement improved with increasing neutron energies up to 20 MeV. At energies >20 MeV, MCNP4B fails to describe dose build-up at the phantom interface and penumbra at the edge of the beam because it does not transport secondary charged particles. The penumbra width, defined as the distance between the 80% and 20% iso-dose levels at 5 cm depth and for a 10×10 cm2 field, was between 0.9 mm and 7.2 mm for neutron energies 10-80 MeV.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14360 (URN)10.1088/0031-9155/45/10/317 (DOI)000089865300017 ()
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2017-12-13
    3. Monte Carlo evaluation of a photon pencil kernel algorithm applied to fast neutron therapy treatment planning
    Open this publication in new window or tab >>Monte Carlo evaluation of a photon pencil kernel algorithm applied to fast neutron therapy treatment planning
    2003 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 48, no 20, p. 3327-3344Article in journal (Refereed) Published
    Abstract [en]

    When dedicated software is lacking, treatment planning for fast neutron therapy is sometimes performed using dose calculation algorithms designed for photon beam therapy. In this work Monte Carlo derived neutron pencil kernels in water were parametrized using the photon dose algorithm implemented in the Nucletron TMS (treatment management system) treatment planning system. A rectangular fast-neutron fluence spectrum with energies 0–40 MeV (resembling a polyethylene filtered p(41)+ Be spectrum) was used. Central axis depth doses and lateral dose distributions were calculated and compared with the corresponding dose distributions from Monte Carlo calculations for homogeneous water and heterogeneous slab phantoms. All absorbed doses were normalized to the reference dose at 10 cm depth for a field of radius 5.6 cm in a 30 × 40 × 20 cm3 water test phantom. Agreement to within 7% was found in both the lateral and the depth dose distributions. The deviations could be explained as due to differences in size between the test phantom and that used in deriving the pencil kernel (radius 200 cm, thickness 50 cm). In the heterogeneous phantom, the TMS, with a directly applied neutron pencil kernel, and Monte Carlo calculated absorbed doses agree approximately for muscle but show large deviations for media such as adipose or bone. For the latter media, agreement was substantially improved by correcting the absorbed doses calculated in TMS with the neutron kerma factor ratio and the stopping power ratio between tissue and water. The multipurpose Monte Carlo code FLUKA was used both in calculating the pencil kernel and in direct calculations of absorbed dose in the phantom.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14361 (URN)10.1088/0031-9155/48/20/005 (DOI)
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2015-03-20
    4. RBE related quantities in fast-neutron therapy beams derived using Monte Carlo calculated charged particle spectra
    Open this publication in new window or tab >>RBE related quantities in fast-neutron therapy beams derived using Monte Carlo calculated charged particle spectra
    Show others...
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:liu:diva-14362 (URN)
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2010-01-13
  • 7.
    Söderberg, Jonas
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Fast Neutron Absorbed Dose Distribution Characteristics int he Energy Range 10–80 MeV1998Report (Other academic)
    Abstract [en]

    The most widely used non-conventional technique for radiation therapy today is fast neutron therapy. Because the neutrons are uncharged, they do not ionize themselves, but liberate secondary, densely ionizing charged particles like protons and a-particles by nuclear reactions in the tissue. In a typical modern neutron therapy facility, a proton beam of about 70 MeV is incident on a thick beryllium target which gives a penetration of the neutron beam which is similar to that obtained with modern megavoltage x-ray therapy facilities.

    In neutron dosimetry, the measurements are often difficult to assess due to the LET dependence of the detector response. In a neutron radiation field, the LET spans over 4 decades as seen in figure 1. The corrections necessary can therefore be large. For this reason, Monte Carlo calculations are a good complement to measurements and make it possible to evaluate the measurements to a higher degree of accuracy. Furthermore, in measurements the spatial resolution is determined by the detector size. Using Monte Carlo, however, it is possible to study high dose gradients as well.

    Due to lack of good cross-section data [1], the optimization possibilities and accuracy in fast neutron therapy are not satisfactory. Therefore, fast neutron therapy cannot compete fairly with other modalities of radiation therapy. In radiation therapy, the aim is to deliver absorbed doses to the tumour within 3.5%. At the same time the neutron kerma factors in carbon have an uncertainty of about 10-15%. Work is now underway in Uppsala, at the The Svedberg Laboratory, to get improved double differential cross-section data for fast neutrons on carbon, nitrogen and oxygen since these are the most common elements in the body. The accuracy in the hydrogen data is already at an acceptable level.

    In the AAPM report no. 7, TE-liquid is suggested as the reference phantom material while the European protocol uses water. Later, it was suggested that water should be the reference phantom material also for the AAPM protocol and in 1989 the ICRU issued a unified protocol. Since the objective of absorbed dose measurements is the absorbed dose to tissue, the following materials are used in this work; water, TE-liquid, standard soft tissue and adipose tissue. The energies presently used in fast neutron therapy are up to about 70 MeV. So in order to test the suitability of water as a reference material for fast neutrons, the energies used are 10, 15, 20, 40, 60 and 80 MeV.

    One problem with the neutron therapy beams is that large penumbra effects reduce the physical selectivity of the beam, i.e., it is more difficult, compared to in megavolt photon beams, to concentrate absorbed doses to the tumour volume while sparing healthy tissues. This is mainly due to the thermalization of the neutrons and the secondary gamma radiation released in neutron capture processes. One aim of this work is therefore to explore how the penumbra effects vary with neutron energy, testing the hypotheses that the penumbra decreases as the neutron energy increases.

    The main aim of this work is to use Monte Carlo techniques to evaluate the penumbra effect due to the transport of secondary particles released by the neutrons in the phantom. Pencil beam data are derived, i.e., the neutron source is assumed to be a point source and the SSD (Source-Skin-Distance) to be infinite. The pencil beam results are integrated to yield results for finite beam areas. Furthermore, the absorbed dose due to photons and their secondary particles will be derived separately and compared to the total absorbed dose as a function of depth. At the reference point, at 5-cm depth, the contribution to kerma rom the different neutron reaction channels will be evaluated by scoring values for the neutron fluence and applying partial cross-section data. Since the codes used are FLUKA and MCNP, a comparison of the results from the codes is made at the energies where both codes are valid, i.e., 10, 15 and 20 MeV.

  • 8.
    Söderberg, Jonas
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Fast neutron dosimetry: a study of basic dosimetric properties of fast-neutrons for external beam radiotherapy and problems associated with corrections of measured charged particle cross-sections2001Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Basic dosimetric properties of fast-neutron beams with energies ≤80 MeV were explored using Monte Carlo techniques. Elementary pencil-beam dose distributions taking into account transport of all relevant types of released charged particles (protons, deuterons, tritons, 3He and a particles) were calculated and used to derive several absorbed dose distributions. Broad-beam depth doses in phantoms of different materials were compared and scaling factors calculated to convert absorbed dose in one material to absorbed dose in another. The scaling factors were in good agreement with available published data and show that water is a good substitute for soft tissue even at neutron energies as high as 80 Me V. The inherent penumbra and fraction of absorbed dose due to photons were also studied, and found to be consistent with published values.

    Treatment planning in fast-neutron therapy is commonly performed using dose calculation algorithms designed for photon beam therapy. These algorithms have limitations in the physical models when applied to neutron beams. Monte Carlo derived neutron pencil-beam kernels were parameterized and implemented into the photon dose calculation algorithms of the TMS (MDS Nordion) treatment planning system. It was shown that these algorithms yield good results in homogeneous water media. However, the heterogeneity correction method of the photon dose calculation algorithm failed to calculate correct results in heterogeneous media for neutron beams.

    Fundamental cross-section data are needed when calculating absorbed doses. To achieve results with adequate accuracy, neutron cross-sections are still not sufficiently well known. At the The Svedberg Laboratory in Uppsala, Sweden, an experimental facility has been designed to measure neutron-induced charged-particle production cross-sections for (n,xp), (n,xd), (n,xt), (n,x3He) and (n,xα) reactions at neutron energies up to 100 MeV. In order to derive the energy distributions of charged particles generated inside the production target, the measured data have to be corrected for the energy lost by the particles in the target. In this work a code (CRAWL) was developed for the reconstruction of the true spectrum. It uses a stripping method. With the limitation of reduced energy resolution, results using CRAWL compare well with those of other methods.

    List of papers
    1. Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study
    Open this publication in new window or tab >>Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study
    2000 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 45, no 10, p. 2987-3007Article in journal (Refereed) Published
    Abstract [en]

    Neutron pencil-beam absorbed dose distributions in phantoms of bone, ICRU soft tissue, muscle, adipose and the tissue substitutes water, A-150 (plastic) and PMMA (acrylic) have been calculated using the Monte Carlo code FLUKA in the energy range 0.5 to 80 MeV. For neutrons of energies ≤20 MeV, the results were compared to those obtained using the Monte Carlo code MCNP4B. Broad-beam depth doses and lateral dose distributions were derived. Broad-beam dose distributions in various materials were compared using two kinds of scaling factor: a depth-scaling factor and a dose-scaling factor. Build-up factors due to scattered neutrons and photons were derived and the appropriate choice of phantom material for determining dose distributions in soft tissue examined. Water was found to be a good substitute for soft tissue even at neutron energies as high as 80 MeV. The relative absorbed doses due to photons ranged from 2% to 15% for neutron energies 10-80 MeV depending on phantom material and depth. For neutron energies below 10 MeV the depth dose distributions derived with MCNP4B and FLUKA differed significantly, the difference being probably due to the use of multigroup transport of low energy (<19.6 MeV) neutrons in FLUKA. Agreement improved with increasing neutron energies up to 20 MeV. At energies >20 MeV, MCNP4B fails to describe dose build-up at the phantom interface and penumbra at the edge of the beam because it does not transport secondary charged particles. The penumbra width, defined as the distance between the 80% and 20% iso-dose levels at 5 cm depth and for a 10×10 cm2 field, was between 0.9 mm and 7.2 mm for neutron energies 10-80 MeV.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14360 (URN)10.1088/0031-9155/45/10/317 (DOI)000089865300017 ()
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2017-12-13
    2. Evaluation of a photon dose calculation algorithm applied to fast-neutron therapy treatment planning using a neutron pencil-beam kernel
    Open this publication in new window or tab >>Evaluation of a photon dose calculation algorithm applied to fast-neutron therapy treatment planning using a neutron pencil-beam kernel
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Treatment planning in fast-neutron therapy is commonly performed using conventional treatment planning systems designed for photon beam therapy. In this work Monte Carlo derived neutron pencil-beam kernels in water were parameterised using an algorithm developed for photon beams and implemented in the TMS photon dose treatment planning system. A rectangular fast-neutron fluence spectrum with energies 0-40 Me V was used. Central axis depth doses and lateral dose distributions were calculated by the dose planning system and compared with corresponding dose distributions using direct Monte Carlo calculations in homogeneous water phantom and heterogeneous phantoms. Good agreement was found in both lateral and depth dose distributions in a homogeneous water phantom. However, considerable deviations were obtained between absorbed doses calculated by the dose planning system and the Monte Carlo calculated absorbed doses in heterogeneous media. The multipurpose Monte Carlo code FLUKA was used both for the calculation of the pencil-beam kernel and in the direct calculations of absorbed dose in the phantom.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-95604 (URN)
    Available from: 2013-07-10 Created: 2013-07-10 Last updated: 2013-07-10
    3. Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods
    Open this publication in new window or tab >>Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods
    2002 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 195, no 3-4, p. 426-434Article in journal (Refereed) Published
    Abstract [en]

    The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x3He) and (n, xα) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.

    Keywords
    Neutron, Cross-section, Charged particle, Energy-loss corrections
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-14359 (URN)10.1016/S0168-583X(02)01090-X (DOI)000178915500023 ()
    Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2017-12-13
  • 9.
    Söderberg, Jonas
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV: a Monte Carlo study2000In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 45, no 10, p. 2987-3007Article in journal (Refereed)
    Abstract [en]

    Neutron pencil-beam absorbed dose distributions in phantoms of bone, ICRU soft tissue, muscle, adipose and the tissue substitutes water, A-150 (plastic) and PMMA (acrylic) have been calculated using the Monte Carlo code FLUKA in the energy range 0.5 to 80 MeV. For neutrons of energies ≤20 MeV, the results were compared to those obtained using the Monte Carlo code MCNP4B. Broad-beam depth doses and lateral dose distributions were derived. Broad-beam dose distributions in various materials were compared using two kinds of scaling factor: a depth-scaling factor and a dose-scaling factor. Build-up factors due to scattered neutrons and photons were derived and the appropriate choice of phantom material for determining dose distributions in soft tissue examined. Water was found to be a good substitute for soft tissue even at neutron energies as high as 80 MeV. The relative absorbed doses due to photons ranged from 2% to 15% for neutron energies 10-80 MeV depending on phantom material and depth. For neutron energies below 10 MeV the depth dose distributions derived with MCNP4B and FLUKA differed significantly, the difference being probably due to the use of multigroup transport of low energy (<19.6 MeV) neutrons in FLUKA. Agreement improved with increasing neutron energies up to 20 MeV. At energies >20 MeV, MCNP4B fails to describe dose build-up at the phantom interface and penumbra at the edge of the beam because it does not transport secondary charged particles. The penumbra width, defined as the distance between the 80% and 20% iso-dose levels at 5 cm depth and for a 10×10 cm2 field, was between 0.9 mm and 7.2 mm for neutron energies 10-80 MeV.

  • 10.
    Söderberg, Jonas
    et al.
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medicine and Health Sciences, Radiation Physics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Ahnesjö, Anders
    Nucletron Scandinavia AB, Uppsala, Sweden.
    Monte Carlo evaluation of a photon pencil kernel algorithm applied to fast neutron therapy treatment planning2003In: Physics in Medicine and Biology, ISSN 0031-9155, Vol. 48, no 20, p. 3327-3344Article in journal (Refereed)
    Abstract [en]

    When dedicated software is lacking, treatment planning for fast neutron therapy is sometimes performed using dose calculation algorithms designed for photon beam therapy. In this work Monte Carlo derived neutron pencil kernels in water were parametrized using the photon dose algorithm implemented in the Nucletron TMS (treatment management system) treatment planning system. A rectangular fast-neutron fluence spectrum with energies 0–40 MeV (resembling a polyethylene filtered p(41)+ Be spectrum) was used. Central axis depth doses and lateral dose distributions were calculated and compared with the corresponding dose distributions from Monte Carlo calculations for homogeneous water and heterogeneous slab phantoms. All absorbed doses were normalized to the reference dose at 10 cm depth for a field of radius 5.6 cm in a 30 × 40 × 20 cm3 water test phantom. Agreement to within 7% was found in both the lateral and the depth dose distributions. The deviations could be explained as due to differences in size between the test phantom and that used in deriving the pencil kernel (radius 200 cm, thickness 50 cm). In the heterogeneous phantom, the TMS, with a directly applied neutron pencil kernel, and Monte Carlo calculated absorbed doses agree approximately for muscle but show large deviations for media such as adipose or bone. For the latter media, agreement was substantially improved by correcting the absorbed doses calculated in TMS with the neutron kerma factor ratio and the stopping power ratio between tissue and water. The multipurpose Monte Carlo code FLUKA was used both in calculating the pencil kernel and in direct calculations of absorbed dose in the phantom.

  • 11.
    Söderberg, Jonas
    et al.
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Faculty of Health Sciences.
    Dangtip, Somsak
    Department of Neutron Research, Uppsala University, Uppsala, Sweden.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Olsson, Nils
    Department of Neutron Research, Uppsala University, Uppsala, Sweden.
    Correction of measured charged-particle spectra for energy losses in the target: A comparison of three methods2002In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 195, no 3-4, p. 426-434Article in journal (Refereed)
    Abstract [en]

    The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x3He) and (n, xα) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.

  • 12.
    Söderberg, Jonas
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics.
    Pettersson, Håkan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Katastrofer orsakade av joniserande strålning2002In: Katastrofmedicin / [ed] Sten Lennquist, Linköping: Linköpings universitet , 2002, 2, p. 303-318Chapter in book (Other academic)
    Abstract [sv]

    Denna bok beskriver hur man ska hantera den svåra uppgiften att bedriva sjukvård på effektivast möjliga sätt i alla de olika typer av situationer där det akuta vårdbehovet överstiger vad som kan klaras med tillgängliga resurser. Den täcker hela omhändertagandekedjan från skadeområdet till definitiv behandling på sjukhus. Denna nya upplaga av Katastrofmedicin är en helt ny bok, utökad till innehållet och uppdaterad mot bakgrund av den omfattande utveckling som präglat detta ämnesområde sedan föregående upplaga.

    Katastrofmedicin kan användas som både läromedel vid utbildning på alla nivåer och som en lättillgänglig handbok och vänder sig till såväl personal i prehospital vård som till läkare och sjuksköterskor på sjukhusens akutmottagningar och inom berörda specialiteter.

1 - 12 of 12
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