| 1. |
- Andreassen, Björn, et al.
(författare)
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Development of a center for advanced tumour imaging and light ion, photon and electron therapy at Karolinska University Hospital.
- 2007
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Ingår i: Gantry Workshop 2007, Verein AUSTRON in the frame of the Interreg IIIA Project.
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Konferensbidrag (populärvet., debatt m.m.)abstract
- This presentation briefly covers the ongoing development of a therapy center with multiple simultaneous radiation modalities at Karolinska university hospital. The hearth of the facility will most likely be a superconducting cyclotron capable of delivering around 400 MeV/u carbon ions simultaneously to two separate excentric gantries who service four treatment rooms each. A number of different stable ions will be available ranging from hydrogen to oxygen but also PET emitting C11 ions and possibly B8 the lightest existing PET emitter. Several treatment rooms will also be equipped for narrow scanned high energy photon and electron beam treatments and a light ion research facility for physics and biology studies will be set up on two separate beamlines. The centre will include an advanced PET-CT and MRSI based diagnostic centre on the same floor and close to both the ion treatment facility and the high energy photon and electron facility. By docking the stereotactic treatment coach both to the treatment units and before and after the treatment to the diagnostic PET-CT units, iso dose delivery can be rapidly examined by imaging the radiation induced C11 and O15 activity produced during the treatment.
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| 2. |
- Andreassen, Björn, 1975-, et al.
(författare)
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Development of an efficient scanning and purging magnet system for IMRT with narrow high energy photon beams
- 2009
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 612:1, s. 201-208
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Tidskriftsartikel (refereegranskat)abstract
- Due to the clinical advantages of Intensity Modulated Radiation Therapy (IMRT) high flexibility and accuracy in intensity modulated dose delivery is desirable to really maximize treatment outcome. Although it is possible to deliver IMRT by using broad beams in combination with dynamic multileaf collimation the process is rather time consuming and inefficient. By using narrow scanned high energy photon beams the treatment outcome can be improved, the treatment time reduced and accurate 3D in vivo dose delivery monitoring is possible by PET-CT based dose delivery imaging of photo nuclear reactions in human tissues. Narrow photon beams can be produced by directing a low emittance high energy electron beam on a thin target, and then cleaning the therapeutic photon beam from transmitted high energy electrons, and photon generated charged leptons, with a dedicated purging magnet placed directly downstream of the target. To have an effective scanning and purging magnet system the purging magnet should be placed immediately after the bremsstrahlung target to deflect the transmitted electrons to an efficient electron stopper. In the static electron stopper the electrons should be safely collected independent of the desired direction of the therapeutic scanned photon beam. The SID (Source to Isocentre Distance) should preferably be short while retaining the ability to scan over a large area on the patient and consequently there are severe requirements both on the strength and the geometry of the scanning and purging magnets. In the present study an efficient magnet configuration with a purging and scanning magnet assembly is developed for electron energies in the 50-75 MeV range and a SID of 75 cm. For a bremsstrahlung target of 3mm Be these electron energies produce a photon beam of 25-17 mm FWHM (Full Width Half Maximum) at a SID of 75 cm. The magnet system was examined both in terms of the efficiency in scanning the narrow bremsstrahlung beam and the deflection of transmitted and photon generated electrons. The simulations show that its is possible to have a scan area on the patient of up to 43 x 40 cm2 for an incident electron energy of 50 MeV and 28 x 40 cm2 at 75 MeV, while at the same time adequately deflecting the transmitted electron beam.
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| 3. |
- Andreassen, Björn, 1975-
(författare)
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Development of improved radiation therapy techniques using narrow scanned photon beams
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis is focused on the development and application of narrow scanned high energy photon beam for radiation therapy. The introduction of physically and biologically optimized intensity modulated radiation therapy (IMRT) requires a flexible and accurate dose delivery method to maximize the treatment outcome. Narrow scanned photon beams is a fast option for IMRT since it is not dependent on mechanically moving heavy collimator leafs and largely independent of the complexity of the desired dose distribution. Scanned photon beams can be produced by scanning an electron beam of low emittance, incident on a thin bremsstrahlung target of low atomic number. The large fraction of high energy electrons that are transmitted through the target has to be removed by a strong purging magnet. In the thesis a strong purging magnet, coupled with a magnetic scanning magnet, is presented for an intrinsic electron energy of 50 - 75 MeV and a source to isocenter distance of 75 cm. The available scan area at isocenter can be as large as 43 x 40 cm2 for an incident electron energy of 50 MeV and 28 x 40 cm2 at 75 MeV. By modifying the existing treatment head of the racetrack microtron MM50, it was possible to experimentally produce relevant dose distributions with interesting properties from 50 MV scanned narrow photon beams while deflecting the transmitted electrons onto a simplified electron stopper. The deflection of the transmitted electrons was studied both experimentally and by the Monte Carlo method. With high energy photons, treatment verification is possible through PET-CT imaging of the positron annihilations induced by photonuclear reactions in the patient. Narrow scanned high energy photon beams is the ideal beam quality since the activation efficiency and the effective photon energy will be more uniform than the filtered photon beam from a full range bremsstrahlung target. The induced 11C activity 50 MV by scanned narrow photon beams was measured using PET-CT imaging and compared with Monte Carlo simulations. The combination of fast flexible dose delivery with treatment verification using PET-CT imaging makes narrow high energy scanned photon beams a very interesting treatment modality for biologically optimized adaptive radiation therapy.
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| 4. |
- Andreassen, Björn, et al.
(författare)
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Fast IMRT with narrow high energy scanned photon beams
- 2011
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405. ; 38:8, s. 4774-4784
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Since the first publications on intensity modulated radiation therapy (IMRT) in the early 1980s almost all efforts have been focused on fairly time consuming dynamic or segmental multileaf collimation. With narrow fast scanned photon beams, the flexibility and accuracy in beam shaping increases, not least in combination with fast penumbra trimming multileaf collimators. Previously, experiments have been performed with full range targets, generating a broad bremsstrahlung beam, in combination with multileaf collimators or material compensators. In the present publication, the first measurements with fast narrow high energy (50 MV) scanned photon beams are presented indicating an interesting performance increase even though some of the hardware used were suboptimal. Methods: Inverse therapy planning was used to calculate optimal scanning patterns to generate dose distributions with interesting properties for fast IMRT. To fully utilize the dose distributional advantages with scanned beams, it is necessary to use narrow high energy beams from a thin bremsstrahlung target and a powerful purging magnet capable of deflecting the transmitted electron beam away from the generated photons onto a dedicated electron collector. During the present measurements the scanning system, purging magnet, and electron collimator in the treatment head of the MM50 racetrack accelerator was used with 3-6 mm thick bremsstrahlung targets of beryllium. The dose distributions were measured with diodes in water and with EDR2 film in PMMA. Monte Carlo simulations with GEANT4 were used to study the influence of the electrons transmitted through the target on the photon pencil beam kernel. Results: The full width at half-maximum (FWHM) of the scanned photon beam was 34 mm measured at isocenter, below 9.5 cm of water, 1 m from the 3 mm Be bremsstrahlung target. To generate a homogeneous dose distribution in a 10 x 10 cm(2) field, the authors used a spot matrix of 100 equal intensity beam spots resulting in a uniformity of collimated 80%-20% penumbra of 9 mm at a primary electron energy of 50 MeV. For the more complex cardioid shaped dose distribution, they used 270 spots, which at a pulse repetition frequency of 200 Hz is completed every 1.36 s. Conclusions: The present measurements indicate that the use of narrow scanned photon beams is a flexible and fast method to deliver advanced intensity modulated beams. Fast scanned photon IMRT should, therefore, be a very interesting modality in the delivery of biologically optimized radiation therapy with the possibility for in vivo treatment verification with PET-CT imaging.
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| 5. |
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| 6. |
- Beaumont, Robin N, et al.
(författare)
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Genome-wide association study of placental weight identifies distinct and shared genetic influences between placental and fetal growth.
- 2023
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Ingår i: Nature genetics. - 1546-1718 .- 1061-4036. ; 55:11, s. 1807-19
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Tidskriftsartikel (refereegranskat)abstract
- A well-functioning placenta is essential for fetal and maternal health throughout pregnancy. Using placental weight as a proxy for placental growth, we report genome-wide association analyses in the fetal (n=65,405), maternal (n=61,228) and paternal (n=52,392) genomes, yielding 40 independent association signals. Twenty-six signals are classified as fetal, four maternal and three fetal and maternal. A maternal parent-of-origin effect is seen near KCNQ1. Genetic correlation and colocalization analyses reveal overlap with birth weight genetics, but 12 loci are classified as predominantly or only affecting placental weight, with connections to placental development and morphology, and transport of antibodies and amino acids. Mendelian randomization analyses indicate that fetal genetically mediated higher placental weight is causally associated with preeclampsia risk and shorter gestational duration. Moreover, these analyses support the role of fetal insulin in regulating placental weight, providing a key link between fetal and placental growth.
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| 7. |
- Brahme, Anders, et al.
(författare)
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Application of Geant4 in the development of new radiation therapy treatment methods
- 2006
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Ingår i: Proceedings of the 9th Conference, Astroparticle, Particle and Space Physics, Detectors and Medical Physics Applications. - 5 Toh Tuck Link, singapore : World Scientific Publishing Co. Pte. Ltd.. - 9812567984 ; , s. 451-461
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Konferensbidrag (refereegranskat)abstract
- There is a very fast development of new radiation treatment methods today, from advanced use of intensity modulated photon and electron beams to light ion therapy with narrow scanned beam based treatment units. Accurate radiation transport calculations are a key requisite for these developments where Geant4 is a very useful Monte Carlo code for accurate design of new treatment units. Today we cannot only image the tumor by PET-CT imaging before the treatment but also determine the tumor sensitivity to radiation and even measure in vivo the delivered absorbed dose in three dimensions in the patient. With such methods accurate Monte Carlo calculations will make radiation therapy an almost exact science where the curative doses can be calculated based on patient individual response data. In the present study results from the application of Geant4 are discussed and the comparisons between Geant4 and experimental and other Monte Carlo data are presented.
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| 8. |
- Eid, Jarle, et al.
(författare)
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Developing local crisis leadership : A research and training agenda
- 2023
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Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 14
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Forskningsöversikt (refereegranskat)abstract
- The crisis triggered by Covid-19 has exposed the interdependencies of modern society and sparked interest in local response to protracted and complex crisis situations. There has been a growing awareness and interest in the key roles of political and professional stakeholders, their emotional regulation and how they influence team performance and outcomes in dealing with uncertainty and complex crisis situations. While cognitive and behavioral aspects of crisis leadership are well researched, less is understood about how one can mitigate negative emotions, instill trust, or restore public faith and support of security forces and emergency response teams during crises. In addressing this gap, we propose a simplified conceptual roadmap for research and training of local crisis leadership. In this, we emphasize complex problem solving, team interaction, team context and technology and team training design. These four factors represent significant barriers if neglected. On the other side, they may be considerable force multipliers when better understood and managed. We suggest how seven research and training questions could be linked to the four conceptual factors and guide an evidence-based approach to develop local crisis leadership.
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| 9. |
- Gurholt, Tiril P., et al.
(författare)
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Intracranial and subcortical volumes in adolescents with early‐onset psychosis : A multisite mega‐analysis from the ENIGMA consortium
- 2020
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Ingår i: Human Brain Mapping. - Stockholm : Wiley. - 1065-9471 .- 1097-0193. ; 43:1, s. 373-384
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Tidskriftsartikel (refereegranskat)abstract
- Early-onset psychosis disorders are serious mental disorders arising before the age of 18 years. Here, we investigate the largest neuroimaging dataset, to date, of patients with early-onset psychosis and healthy controls for differences in intracranial and subcortical brain volumes. The sample included 263 patients with early-onset psychosis (mean age: 16.4 ± 1.4 years, mean illness duration: 1.5 ± 1.4 years, 39.2% female) and 359 healthy controls (mean age: 15.9 ± 1.7 years, 45.4% female) with magnetic resonance imaging data, pooled from 11 clinical cohorts. Patients were diagnosed with early-onset schizophrenia (n = 183), affective psychosis (n = 39), or other psychotic disorders (n = 41). We used linear mixed-effects models to investigate differences in intracranial and subcortical volumes across the patient sample, diagnostic subgroup and antipsychotic medication, relative to controls. We observed significantly lower intracranial (Cohen's d = −0.39) and hippocampal (d = −0.25) volumes, and higher caudate (d = 0.25) and pallidum (d = 0.24) volumes in patients relative to controls. Intracranial volume was lower in both early-onset schizophrenia (d = −0.34) and affective psychosis (d = −0.42), and early-onset schizophrenia showed lower hippocampal (d = −0.24) and higher pallidum (d = 0.29) volumes. Patients who were currently treated with antipsychotic medication (n = 193) had significantly lower intracranial volume (d = −0.42). The findings demonstrate a similar pattern of brain alterations in early-onset psychosis as previously reported in adult psychosis, but with notably low intracranial volume. The low intracranial volume suggests disrupted neurodevelopment in adolescent early-onset psychosis.
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| 10. |
- Holmberg, Rickard, et al.
(författare)
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Development of Methods for the Design of Electron Collection Systems for Scanned Thin-target Bremsstrahlung IMRT
- 2007
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Ingår i: 9th Biennial ESTRO Meeting on Physics and Radiation Technology for Clinical Radiotherapy, 8-13 Spetember, Barcelona, Spain.
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Purpose: Driven by the need for more accurate and cost-effective therapeutic methods, IMRT is rapidly being deployed at radiation therapy departments. An effecient way of conducting IMRT is by using narrow scanned photon beams, produced from thin bremsstrahlung production targets. Thereby the photon penumbra and pencil beam half width are minimized, while the mean photon energy in the beam is increased, thus enhancing the quality of PET-CT dosimetry. This approach, however, imposes the additional problem of deflecting and stopping an intense stream of high-energy transmitted electrons. In this work, methods for resolving this problem was developed and applied to different treatment unit configurations.Materials/Method: To optimize the geometrical shape of the electron collector together with the scanning and purging magnetic fields, a composite framework, including CAD (Solid Edge 3D), electromagnetic field simulation (Opera 3D) and Monte Carlo simulation (GEANT4), has been set up. Codes have been developed to integrate the geometry from the CAD software as well as the magnetic fields from the electromagnetic design software in the Monte Carlo simulation, so that all three components have one common description of the physical device investigated. Additionally, software has been developed to enable the results from the Monte Carlo simulation to be directly fed back into the CAD model, permitting the use of analytical models for the electron collector shape as a function of transmitted electron fluence from the target. A major consideration in the choice of GEANT4 as the Monte Carlo simulation software was the ability to simulate all relevant kinds of produced radiation in the electron collector.Results: The integration of the geometries and the magnetic fields in the different software applications has been thouroughly verified by several means. For example, tracking a 50 MeV electron through the magnetic fields independently in GEANT4 and Opera 3D gives a maximum disagreementof about 500 nm - well within the expected numerical accuracy. The leakage radiation from a number of different collector designs is evaluated and compared to the ICRP 33 recommendations.Conclusions: A framework integrating CAD, FEM simulations and Monte Carlo transport was developed. The framework, which is more generelly applicable, was here applied to the modelling and simulation of electron collectors for scanned, narrow photon beam IMRT. Relevant physical quantities, including leakage radiation, was computed and evaluated.
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