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Motivationen med studien var den alldeles för höga stråldosen som används vid CTundersökningar. I de allra flesta fallen anpassas man inte rörströmmen efter patientens storlek och därmed får smalare patienter en onödigt hög stråldos. Målet var att reducera stråldosen till patienter som undersöks med datortomografi utan att minska på bildkvalité, genom att anpassa rörströmmen efter patientens stoIn this study we have investigated the possibilities of dose reduction in CT at a constant level of image quality by adjustment of the tube current to the phantom size. The motivation with the study is the high radiation doses to the patients and the increasing frequency of CT examinations and the variety of examinations in CT, and that the same tube current is used for different patient sizes. Ac

Funktionell magnetresonanstomografi (fMRI) är en teknik som gör det möjligt att kartlägga aktivering inom olika delar av hjärnan. Genom att samla in bilddata då patienten är i vila, och sedan jämföra dessa med data insamlade medan patienten är aktiv (t.ex. utför fingerrörelser), kan en bild skapas som visar var i hjärnan aktivering har skett. Dessa bilder kan t.ex. användas för att bedöma om det äFunctional MRI (fMRI) is a technique for determining which parts of the brain are activated when a subject experiences some type of physical sensation or performs an activity. This technique has during the past several years become a very useful tool for understanding functions of the nervous system, and the development of clinical applications is rapidly progressing. However, fMRI is not straight

Effects of flow are a fundamental part of magnetic resonance imaging (MRI). Since almost every part of the body contains some kind of flow, the effects are seen in generally all MR images. The presence of flow in an image slice may be a vast source of artefacts but the effects of flow can also be used for diagnostic purposes, for example in magnetic resonance angiography (MRA). In MRA, flow effect

Diffusionsviktad magnetiskresonanstomografi (MRT) är en metod där vi med hjälp av magnetfält kan märka in vattenmolekyler och följa de slumpmässiga rörelser som alla molekyler uppvisar. Den slumpmässiga rörelsen uppstår p.g.a. termisk energi (värmeenergi) och varierar med temperaturen och ämnet som omger molekylerna. Tensoranalys är ett matematiskt verktyg för att skapa modeller för hur den omgivaDiffusion weighted magnetic resonance imaging (MRI) is a modality that offers the possibility to measure molecular motion such as water self-diffusion which is in the order of 10-9 m2/s. The basic formalism has been known since the middle of the 20:th century, it is however, only during the last decade that it has been used for imaging. Through tensor analysis of diffusion weighted images, acquire

Up to recently mobile gamma spectrometry has mostly been performed with NaI(Tl)-based detector systems. However lately the interest of using HPGe(High Purity Germanium)-based systems have increased and one has realised that the excellent energy resolution of HPGe-detectors, in combination with the possibility to manufacture larger crystals than before, is an advantage not only when performing in s

A patient positioning system for Boron Neutron Capture Therapy (BNCT) for treatment of brain tumours was designed, and its accuracy was evaluated. The system will be used at the BNCT facility under construction at Studsvik, Sweden. Recent studies have shown that the accuracy in the patient positioning procedure in BNCT is of more significance than generally perceived in the past. Therefore one obj

Idag behandlas många former av cancer med joniserande strålning från linjäracceleratorer. Målet med behandlingen är att sterilisera cancercellerna med så liten påverkan som möjligt på den friska vävnaden. För att uppnå detta är det viktigt att ha en så bra bestämning som möjligt av den absorberade dosen till tumör- och normalvävnad. För detta ändamål används idag tredimensionella dosplaneringssystA Monte Carlo generated linear accelerator is implemented into a pencil beam based treatment planning system (TPS) to study the possibility to verify the TPS with a Monte Carlo method. The implemented accelerator is then used to study two inhomogeneous lung geometries; lungslab and mediastinium. Advantages of a Monte Carlo method over conventional measurements are that accelerator output variation

Diffusion is a molecular phenomenon and can be described as the process by which matter is transported from one part of a system to another as a result of random molecular motion. The diffusion coefficient is then a quantity that describes the mobility of the molecules in a media. In recent years, methods have been developed to image the diffusion of water in human tissue using magnetic resonance

"At searching for lost point sources, it is important to use an optimal search strategy and an optimal methodology for spectrum data analysis. The purpose of this work is to evaluate a simple on-line method for locating lost point sources in the environment with carborne gamma spectrometry and study different strategies for detector geometries and speed of the car. The scope of this thesis

The characterization of the incident photon beam is usually divided into its dependence on collimator setting (head-scatter factor) and off-axis position (primary off-axis ratio). These parameters are normally measured "in air" with a build-up cap, thick enough to generate full dose build-up at the depth of dose maximum. In order to prevent any influence from contaminating electrons, it

In this report the characteristics of the electron applicator system for an Elekta SLi Plus linear accelerator have been studied. The investigation will serve as a basis for a new applicator design that will give less radiation leakage. The present applicator system does not fully comply with the recommendations of the International Electrotechnical Commission (IEC) Standards recording radiation l

Yttrium-90 is a pure β-emitting radionuclide with a high energy (Emax = 2.28 MeV) and a short half-life (T½ = 64.1 h). It has shown to be a promising isotope to use in radio-immunotherapy. In the absence of direct photon emission scintillation camera imaging can be obtained by acquiring events from bremsstrahlung photons created at or near the decay site of the radionuclide. It is, however, not ev

I dag får en stor del av alla cancerpatienter strålbehandling. Den joniserade strålningen har mycket hög energi och ambitionen är att slå ut hela tumören samtidigt som man skonar den omgivande friska vävnaden i största möjliga mån. Efter bestrålning reparerar cellerna sig till stor del. Eftersom friska celler reparerar sig i högre utsträckning än tumörceller, delar man upp behandlingen i flera beh"Purpose: To find the optimal correction strategy to decrease the set-up errors for pelvic patients at the Department of Radiation Physics at the Finsen Centre, Copenhagen University Hospital. Materials and methods: Using electronic portal imaging devise (EPID), 765 portal images from 17 patients, treated for bladder-, rectum-, anus- or gynecologic-carcinoma were aquired. The patients had th

Idag behandlas cancer med bl.a. strålbehandling, tyvärr ger denna många gånger biverkningar. Detta beror på att strålningen inte bara skadar cancerceller utan även friska celler, eftersom strålningen måste passera frisk vävnad för att nå in till cancertumören. Det har nyligen utvecklats en ny strålbehandlingsteknik som kan minska strålningen till frisk vävnad samtidigt som tumören ges en hög strål"Intensity modulated radiation therapy (IMRT) is a fairly new modality in the treatment of cancer with radiotherapy. The original idea is Swedish and has existed for more than 20 years. But it is only in recent years that clinics have implemented the IMRT technique. IMRT uses many segments (small subfields) that build up radiation fields with nonuniform energy fluence. With this technique, be

The purpose of this study was to obtain more knowledge of the parameters affecting the production of 45Ti utilizing the nuclear reaction 45Sc(p,n) 45Ti. Titanium-45 decays by +-decay and E.C. to 45Sc with a half-life of 3,08 h. These properties make the radionuclide suitable for positron emission tomography (PET).The work was carried out at the Department of Physics in Lund using the V

Cancer är en otrevlig sjukdom, som drabbar många människor. Man söker ständigt nya och bättre sätt att bota patienter eller åtminstone lindra sjukdomens framfart. Ett vanligt sätt att behandla cancer är med strålning. Strålningen kan bestå av sk fotoner. Fotoner är samma slags partiklar som t.ex. vanligt ljus. Skillnaden är att de fotoner som används vid strålbehandling av cancer har högre energi "Purpose: The aim of this study was to investigate whether inversely planned intensity modulated radiation therapy (IMRT), using the clinical radiotherapy equipment at hand in our department, renders any advantages regarding dose distribution over conventional radiotherapy for head and neck cancer patients in the ARTSCAN (Accelerated RadioTherapy of Squamous cell Carcinoma in the head And Nec

Cisplatin is a cytostatic agent that has been used for more than 30 years in the treatment of a wide spectrum of tumours. The clinical use is limited by its side effects, primarily renal toxicity. An enhanced anti tumour effect has been demonstrated for radioactive (191Pt) cisplatin both in in vitro and in vivo models by our group. The purpose of the present study was to compare the side effects f

För att uppskatta risker av joniserande strålning används begreppet absorberad dos, som är den absorberade energin per massenhet i ett organ. För radioaktiva läkemedel är absorberad dos inte direkt översättbart till risk, bland annat pga heterogena fördelningar av aktivitet på både vävnads- och cellnivå. Denna heterogenitet kan inte mätas med dagens scintillationskamera, då denna har en upplösningThe purpose of this thesis has been to learn the MCNP-code, its theory and limitations, and how to use it in the field of small-scale dosimetry. In order to evaluate the applicability of the code for future dosimetry studies it was applied on a novel small-intestinal dosimetry model. For some radiopharmaceuticals a significant amount of activity is excreted through the gastrointestinal tract. It h

Purpose: For evaluation, development and optimization of treatment strategies in radionuclide therapy, it is useful to study and model the pharmacokinetics of the therapeutic agent. The aim of this study was to create models for describing the pharmacokinetics of monoclonal antibodies used for radioimmunotherapy.Method: Two models, based on very different modeling approaches, are presented in this

Många av dagens cancerpatienter får strålbehandling. Den strålning som produceras i en strålbehandlingsapparat är av två olika slag: elektronstrålning och fotonstrålning. Vanligt ljus är också fotonstrålning, men fotonstrålningen som används inom strålbehandling är mycket mer energirik och kallas med ett annat namn för röntgenstrålning. Inför en strålbehandling görs mycket planering utav ett team "This project concerns the precise characterization of one of the VARIAN accelerators used in the radiotherapy clinic at the Finsen Centre at Copenhagen University Hospital, Denmark. Detailed characteristics of the clinical beam incident on the patient are almost impossible to measure. Even though manufacturers provide the necessary information about the specific accelerator, the models are c