| 1. |
- Adrian, Gabriel, et al.
(author)
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The FLASH effect depends on oxygen concentration
- 2019
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In: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 93:1106
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Recent in vivo results have shown prominent tissue sparing effect of radiotherapy with ultra-high dose rates (FLASH) compared to conventional dose rates (CONV). Oxygen depletion has been proposed as the underlying mechanism, but in vitro data to support this have been lacking. The aim of the current study was to compare FLASH to CONV irradiation under different oxygen concentrations in vitro. METHODS: Prostate cancer cells were irradiated at different oxygen concentrations (relative partial pressure ranging between 1.6 and 20%) with a 10 MeV electron beam at a dose rate of either 600 Gy/s (FLASH) or 14 Gy/min (CONV), using a modified clinical linear accelerator. We evaluated the surviving fraction of cells using clonogenic assays after irradiation with doses ranging from 0 to 25 Gy. RESULTS: Under normoxic conditions, no differences between FLASH and CONV irradiation were found. For hypoxic cells (1.6%), the radiation response was similar up to a dose of about 5-10 Gy, above which increased survival was shown for FLASH compared to CONV irradiation. The increased survival was shown to be significant at 18 Gy, and the effect was shown to depend on oxygen concentration. CONCLUSION: The in vitro FLASH effect depends on oxygen concentration. Further studies to characterize and optimize the use of FLASH in order to widen the therapeutic window are indicated. ADVANCES IN KNOWLEDGE: This paper shows in vitro evidence for the role of oxygen concentration underlying the difference between FLASH and CONV irradiation.
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| 2. |
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| 3. |
- Aznar, MC, et al.
(author)
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Real-time optical-fibre luminescence dosimetry for radiotherapy: physical characteristics and applications in photon beams
- 2004
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In: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 49:9, s. 1655-1669
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Journal article (peer-reviewed)abstract
- A new optical-fibre radiation dosimeter system, based on radioluminescence and optically stimulated luminescence from carbon-doped aluminium oxide, was developed and tested in clinical photon beams. This prototype offers several features, such as a small detector (1 x 1 x 2 mm), high sensitivity, real-time read-out and the ability to measure both dose rate and absorbed dose. The measurements describing reproducibility and output dependence on dose rate, field size and energy all had standard deviations smaller than 1%. The signal variation with the angle of incidence was smaller than 2% (1 SD). Measurements performed in clinical situations suggest the potential of using this real-time system for in vivo dosimetry in radiotherapy.
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| 4. |
- Baldoc, C, et al.
(author)
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Dose resolution in radiotherapy polymer gel dosimetry: effect of echo spacing in MRI pulse sequence
- 2001
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In: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 46:2, s. 449-460
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Journal article (peer-reviewed)abstract
- In polymer gel dosimetry using magnetic resonance imaging, the uncertainty in absorbed dose is dependent on the experimental determination of T2. The concept of dose resolution (Dpdelta) of polymer gel dosimeters is developed and applied to the uncertainty in dose related to the uncertainty in T2 from a range of T4 encountered in polymer gel dosimetry. Dpdelta is defined as the minimal separation between two absorbed doses such that they may be distinguished with a given level of confidence, p. The minimum detectable dose (MDD) is Dpdelta as the dose approaches zero. Dpdelta and the minimum detectable dose both give a quantifiable indication of the likely practical limitations and usefulness of the dosimeter. Dpdelta of a polyacrylamide polymer gel dosimeter is presented for customized 32-echo and standard multiple-spin-echo sequences on a clinical MRI scanner. In evaluating uncertainties in T2, a parameter of particular significance in the pulse sequence is the echo spacing (ES). For optimal results, ES should be selected to minimize Dpdelta over a range of doses of interest in polymer gel dosimetry.
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| 5. |
- Bjoreland, Anders, et al.
(author)
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Liquid ionization chamber calibrated gel dosimetry in conformal stereotactic radiotherapy of brain lesions
- 2008
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In: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 47:6, s. 1099-1109
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Journal article (peer-reviewed)abstract
- Hypofractionated conformal stereotactic radiotherapy (HCSRT) is an established method of treating brain lesions such as arteriovenous malformations (AVMs) and brain metastases. The aim of this study was to investigate the reliability of treatment plans in the terms of dose distribution and absorbed dose for HCSRT. Methods and materials. Treatment plans for three different clinical intracerebral targets, AVMs, were transferred to a CT study of a spherical water filled phantom simulating the human head and recalculated for the phantom geometry using a standard treatment planning system utilizing a pencil beam algorithm for dose calculation. The calculated absorbed dose, relative three dimensional (3D) dose distribution and dose conformity were investigated using gel dosimetry normalized to liquid ionization chamber (LIC) measurements. Results. The measured absorbed dose to the dose reference point was found to be within 2% of the calculated dose for all three targets. The measured dose distribution was found to be within 3% and 2 mm of the calculated dose for more than 93% of all points in the target volume for all three targets. Conclusions. The results show that the investigated standard treatment planning system can correctly predict the absorbed dose and dose distribution in different types of intracerebral targets and that the treatment can be delivered according to the plan.
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| 6. |
- Bäck-Pettersson, Siv, 1946, et al.
(author)
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FOU-kompetensförsörjningsprogram för sjuksköterskor i Fyrbodal
- 2012
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Reports (other academic/artistic)abstract
- Sammanfattning Betydelsen av FoU-kompetensförsörjningsprogrammet som varit en medveten och strategisk satsning inom FoU-området kan sammanfattas på följande sätt: Deltagarnas behållning och föreskriven akademisk utveckling har haft en närmast hundraprocentig måluppfyllelse och gett kliniskt verksamma sjuksköterskor en bra start på sin akademiska karriär. Programmet illustrerar ett effektivt sätt att stimulera sjuksköterskors livslånga lärande genom att bygga upp förmågan att genomföra och tillämpa omvårdnadsforskning i klinisk praktik. Programmet har också bidragit till utvecklingen av kompetenta handledare för studenter under utbildning. Flertalet av deltagarna har utvecklat både en önskan om och kompetens för att ta på sig ledande uppdrag såväl inom den egna verksamheten som i gränsöverskridande projekt både inom Fyrbodal och nationellt. Programmet har medverkat till att bryta revirtänkande och kan bidra till en mer öppen och gränsöverskridande kultur inom Fyrbodalområdets hälso- och sjukvård. Det har även medverkat till att deltagarna skaffat sig en helhetssyn på och förståelse för olika vårdverksamheter. Programmets design kan användas för att utveckla såväl professionell som vetenskaplig kompetens och kan med fördel användas inom andra yrkesgrupper med medellång vårdutbildning, eller för en tvärprofessionell grupp.
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| 7. |
- Bäck-Pettersson, Siv, 1946, et al.
(author)
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Nurses´Experiences of participation in a research and development programme
- 2013
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In: Journal of Clinical Nursing. - : Wiley. - 0962-1067 .- 1365-2702. ; 22:7-8, s. 1103-1111
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Journal article (peer-reviewed)abstract
- Aims and objectives. To describe clinical nurses’ experience of participating in a Research and Development (R&D) programme and its influence on their research interest and ability to conduct and apply nursing research. Background. To stimulate nurses’ research interest and to overcome barriers for building research capacity in nursing, there is a need for sustainable research programmes. A two-year programme was designed for nurses, to take part in both an academic education for master and research seminars and workshops to conduct a research project from idea to publication. Design. A qualitative approach using using focus group interviews. Methods. Registered nurses (n = 12) with a bachelor’s degree in nursing, participated. Data were collected in focus group interviews, after one year and when the programme ended. Content analysis was used to analyse the data. Results. The findings consist of two themes: being a traveller in the world of nursing research, which included three categories, and experiencing professional growth as a result of nursing research training, in both cases focusing on the experience of students involved in a cohesive programme which included four categories: discovering new dimensions of clinical nursing practice; selected and confirmed; supported by professional others; development of professional self-concept. Conclusions. To support early career researchers, there is a need for strong leadership, an organisational and supportive infrastructure underpinning research capability building in nurses. In this context, research strategies, programmes and collaboration between leaders of academia and clinical institutions appear to be essential. Relevance to clinical practice. The R&D programme illustrates an effective way of stimulating nurses’ lifelong learning by building the capacity to conduct and apply nursing research in clinical practice. The structure of the programme can be used as a model in other contexts.
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| 8. |
- Bäck, Sven, et al.
(author)
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Ferrous sulphate gel dosimetry and MRI for proton beam dose measurements
- 1999
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In: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 44:8, s. 1983-1996
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Journal article (peer-reviewed)abstract
- Ferrous sulphate gel dosimetry has the potential for measurement of absorbed dose distributions in proton therapy. The chemical properties of the gel are altered according to the radiation dose and these changes can be evaluated in three dimensions using MRI. The purpose of this work was to investigate the properties of a ferrous gel used with clinical proton beams. The gel was irradiated with both monoenergetic and range-modulated proton beams. It was then evaluated using MRI. The depth dose by means of the 1/T1 distribution was studied and compared with data from a plane-parallel plate ionization chamber. 1/T1 was shown to be proportional to the dose at a mean proton energy of approximately 90 MeV. The dose response was no different from that obtained using photon beams. However, on normalization at the entrance, the relative 1/T1 at the Bragg peak was 15-20% lower than the corresponding ionization chamber data for the monoenergetic proton beam. Better agreement was found for the modulated beam, but with significant differences close to the distal edge of the 1/T1 distribution. The change in sensitivity with depth was explained by means of a linear energy transfer dependence. This property was further studied using Monte Carlo methods.
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| 9. |
- Bäck, Sven
(author)
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Implementation of MRI gel dosimetry in radiation therapy
- 1998
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Doctoral thesis (other academic/artistic)abstract
- Gel dosimetry was used together with magnetic resonance imaging (MRI) to measure three-dimensional absorbed dose distributions in radiation therapy. Two different dosimeters were studied: ferrous- and monomer gel, based on the principles of radiation-induced oxidation and polymerisation, respectively. Single clinical electron and photon beams were evaluated and gel dose distributions were mainly within 2% of conventional detector results. The ferrous-gel was also used for clinical proton beams. A decrease in signal per absorbed dose was found close to the end of the range of the protons (15-20%). This effect was explained as a linear energy transfer dependence, further supported with Monte Carlo simulations. A method for analysing and comparing data from treatment planning system (TPS) and gel measurements was developed. The method enables a new pixel by pixel evaluation, isodose comparison and dose volume histogram verification. Two standard clinical radiation therapy procedures were examined using the developed TPS verification method. The treatment regimes included several beams of different radiation qualities. The TPS calculated data were in very good agreement with the dose distribution measured by the ferrous-gel. However, in a beam abutment region, larger dose difference was found. Beam adjustment errors and a minor TPS underestimation of the lateral scatter contribution outside the primary electron beam may explain the discrepancy. The overall uncertainty in the ferrous-gel dose determination was considerably reduced using an optimised MRI acquisition protocol and a new MRI scanner. The relative dose uncertainty was found to be better than 3.3% for all dose levels (95% confidence level). Using the method developed for comparing measured gel data with calculated treatment plans, the gel dosimetry method was proven to be a useful tool for radiation treatment planning verification.
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| 10. |
- Bäck, Sven, et al.
(author)
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Improvements in absorbed dose measurements for external radiation therapy using ferrous dosimeter gel and MR imaging (FeMRI)
- 1998
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In: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 43, s. 261-
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Journal article (peer-reviewed)abstract
- A ferrous gel, based on ferrous (Fe) sulphate and agarose, was used with a clinical magnetic resonance imaging (MRI) scanner to obtain relative dose distribution data from therapeutic photon and electron beams. The FeMRI gel was scanned using a new MRI acquisition protocol optimized for T1 measurements. Thorough comparisons with silicon semiconductor detector and ionization chamber measurements, as well as with Monte Carlo calculations, were performed in order to quantify the improvements obtained using FeMRI for dose estimations. Most of the relative doses measured with FeMRI were within 2% of the doses measured with other methods. The larger discrepancies (2-4%) found at shallow depths are discussed. The uncertainty in relative dose measurements using FeMRI was significantly improved compared with previously reported results (5-10%, one standard deviation, 1 SD), and is today between 1.6% and 3.3% (depending on dose level, 2 SD). This corresponds to an improvement in the minimum detectable dose (3 SD above background) from approximately 2 Gy to better than 0.6 Gy. The results obtained in this study emphasize the importance of obtaining basic FeMRI dose data before the method is extended to complicated treatment regimes.
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