| 1. |
- Palmqvist, Charlotte, et al.
(författare)
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Sexuellt beteende hos daghemsbarn
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet är att studera daghemsbarns sexualitet i åldrarna 2 - 5 år. I en stor stad valdes 11 daghem ut slumpmässigt bland över 100 st. I fas I intervjuades en slumpmässigt vald personal på varje daghem för att utröna vilka sexuella beteenden som förekommer och hur de bemöts. I fas II skattade ytterligare två slumpvis valda personer från varje daghem vanligheten för respektive ålder och kön gällande de beteenden som framkom i den första fasen. Sammanlagt deltog därmed 33 personal. I den explorativa fasen framkom nio beteenden: pratsexualitet, onani, samlagsrörelser, tar på personalen-intim beröring, förälskelse mellan pojke och flicka, jaga-lek, leka sexuella lekar, teckningar och visa sitt kön för andra. För några beteenden fanns en tendens till ökning med åldern och några ökade inte.
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| 2. |
- Carlsson, Per, 1951-, et al.
(författare)
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An evaluation of prostate cancer screening using a decision analytic model
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- As early prostate cancer is often asymptomatic, the disease is often not diagnosed until it has reached an advanced, incurable stage. However, if diagnosed when it is still confined to the prostate, prostate caner is potentially curable. At present, there are no completed prospective evaluations or other scientific evidence to suggest that prostate cancer mortality is reduced or that quality of life is increased either by curative treatment or by screening programmes. However, the potential effects of a screening programme can be modelled using decision analytic computer software.The aim of this project was to develop a model for comparing the expected quality-adjusted life expectancy for a group of men subjected to a programme of screening for prostate cancer to that of a control group with conventional case-finding, given limited empirical data on the effectiveness of both strategies.Due to limitations of existing data, the analysis was developed during the early stages of evaluating a prostate cancer screening programme. We wish to illustrate how an analytic tool such as this model can be used in the future.The model was functionally separated into two parts. The first part, the observation submodel, covers the first 6 years of the programme and classifies the screened population into different quality of life states, based on observed outcomes. The second part, the simulation submodel, predicts quality adjusted life-years for healthy participants and for prostate cancer patients who receiving curative treatment or expectant management. Data for the model were obtained from a pilot programme on screening for prostate cancer in which a randomly selected population sample has been screened by digital rectal examination in Norrköping Sweden in 1987 and 1990. The outcome evaluated in the model was quality-adjusted life expectancy for individuals in the cohort invited to the screening programme, compared to results for population controls.While the preliminary results identify some health benefits associated with screening, more accurate empirical data for a number of key variables could improve the evaluation. One feature of this model is that it combines solid, empirical data from the observation submodel with simulated results. When better empirical data on the actual consequences of different strategies are available, they can easily be analysed by using this model.
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| 3. |
- Carlsson, Sten
(författare)
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Liquid Scintillation Counting
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In liquid scintillation counting (LSC) we use the process of luminescense to detect ionising radiation emit$ed from a radionuclide. Luminescense is emission of visible light of nonthermal origin. 1t was early found that certain organic molecules have luminescent properties and such molecules are used in LSC. Today LSC is the mostwidespread method to detect pure beta-ernitters like tritium and carbon-14. 1t has unique properties in its efficient counting geometry, deteetability and the lack of any window which the betaparticles have to penetrate. These properties are achieved by solving the sample to measure in a scintillation cocktail composed of an organic solvent and a solute (scintillator). Even if LSC is a weil established measurement technique, the user can run into problems and abasic knowledge of the deteetor and its different components is of fundamental importance in a correct use of the technique. The alm of this presentation is to provide the user with some of this fundamental knowledge.
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| 4. |
- Lamm, Inger-Lena, et al.
(författare)
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Modulationsöverföringsfunktionen (MTF) : De matematiska grunderna med exempel
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vid överföring av information kan man karakterisera ett överföringssystem på olika sätt. Man kan t.ex. ange hur en signal förstärks, hur den förvr~ngs (distorderas), hur mycket brus systemet innehåller etc. Ett bildgivande system kan i princip karakteriseras av ett objekt som ger en insignal till en detektor vars utsignal antagligen innehåller signal + brus. För att beskriva hur utsignalen ser ut i jämförelse med insignalen används flera begrepp som: Punktspridningsfunktionen (PSF) Linjespridningsfunktionen (LSF) Halvvärdesbredden (FWHM) Inom bildöverförande system använder man sig av begreppet MTF (MTF= Modulation Transfer Eunction) . Vi skall i det följande gå igenom grunderna för MTF och även ge exempel på hur man beräknar MTF. Genom att införa Fourier-transformen kan man lättare beräkna MTF och vi kommer därför att beskriva denna. För mätning av MTF för olika system inom röntgendiagnostiken hänvisas-till litteraturen.
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| 5. |
- Lund, Eva, et al.
(författare)
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Experimental determination of the angular dependence of the directional dose equivalent, H’(d), for ISO “narrow” X ray fields and 137Cs γ-rays measured in a PMMA sphere and a PMMA slab phantom
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- For the purpose of calibrating individual dosimeters in X-ray fields conversion factors from air kerma free in air to dose equivalent at a specified depth in a phantom have been calculated among others by Grosswendt (1991, 1992). By means of Monte Carlo calculations the angular dependence factor for photon beams of oblique incidence is also studied for different phantom shapes and compositions as well as for different X-ray qualities. However, till now there has been a lack of experimental verification of the angular dependence factors. In this investigation the conversion factor from air kerma to Hp(10) has been determined for the following X-ray qualities: 40 kV, 80 kV, and 295 kV, ISO "narrow" spectra and for 137Cs γ-rays using thermoluminescent (TL) dosimeters. The angular dependence factor H'(10,α)/H'(10,0o) has also been experimentally determined for the same X-ray and γ -ray qualities and for different angles between 0o and 180o. The conversion factors are found to be in good agreement with the calculated ones for the PMMA sphere phantom, while some minor discrepancies are found between the experimental and calculated angular dependence factors for the 30x30x15cm3 PMMA slab phantom. The difference in angular dependence obtained for the slab and the sphere is discussed as well as the possibility to underestimate the personal dose equivalent, Hp(10), compared to effective dose, E.
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| 6. |
- Sandborg, Michael, et al.
(författare)
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The choice of anti-scatter grids in diagnostic radiology : the optimization of image quality and absorbed dose
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A Monte Carlo model is developed to study and optimise the design of antiscatter grids in diagnostic radiology. The imaging chain including X-ray energy spectra, phantom (representing the patient), grid and image receptor is simulated. Image quality is quantified in terms of contrast (conventionai screen-film imaging) and signal-to-noise ratio, SNR (digital imaging) and the radiation detriment to the patient (risk) by the mean absorbed dose in the phantom. The advantages of using fibre instead of aluminium for grid interspaces and covers are quantified. Compared to aluminium grids, the absorbed dose is reduced by 10-50%, contrast is improved by 0-10% and SNR by 10-40% (digital radiography). The advantages are larger at low tube potentials and for grids with high ratio and low strip density. Commercial grids, with different interspace materials, strip density, strip width and grid ratio, are compared in paediatric, lumbar spine and chest examinations. The differences in dose increase and contrast improvement factors obtained with these grids are mainly due to the use of different materials in the grid interspaces, but the strip design is also important. In a global optimisation of grid design and tube potential at fixed contrast, it is found that grids of different strip density and ratio all can have good performances provided that they are used with appropriate strip width and tube potential. In the paediatric examination, low ratio grids need thinner strips than used today to be optimal. A small air gap could alternatively be used. In examinations with more scatter (adult AP), present commercial grids are optimal (r=12-16, d=30-50µm). In the lateral view (even more scatter), grids with ratios larger than 16 are optimal provided the grid can be accurately aligned in the beam. The optimization is performed with grids with fibre interspaces and covers since low atomic number materials should preferably be used for materials between the patient and the receptor. Optimal grids with aluminium for these components have lower grid ratio and higher strip densities than optimal fibre grids.
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