Introduction: In conventional medical linear accelerators, the flattening filter is introduced in the photon beam line to provide a uniform lateral dose profile at a specified depth in water. For some radiotherapy treatments, e.g. intensity modulated radiotherapy, a flat radiation field is not necessary and the flattening filter could be removed. Several studies have shown that removal of the filt

Bröstcancer är den vanligaste cancertypen hos kvinnor i Sverige. Nästan 7000 drabbas och ungefär 1600 avlider årligen som en följd av bröstcancer. Sedan man började med regelbundna hälsoundersökningar med mammografi (så kallad ”screening”) har dödligheten minskat betydligt. Vid konventionell mammografi tas tvådimensionella (2D) röntgenbilder av bröstet. Detta generar en bild som avspeglar röntgensThe purpose of this work is to explore and quantify physical metrics of breast tumors in both magnetic resonance imaging (MRI) and breast tomosynthesis (BT) images, and relate these metrics to patho-physiological and histopathological bindings. An analysis of breast specimens containing tumors will be employed to determine BT metrics of interest. These metrics will then be applied to patient image

Prostatacancer är den vanligaste cancersjukdomen bland män i Sverige och drabbar framförallt äldre. Eftersom sjukdomsförloppet normalt sett är långsamt hinner de flesta män avlida av någon helt annan sjukdom eller orsak. Dock finns där en grupp av män som drabbas av en betydligt aggressivare form av prostatacancer som i ett tidigt skede börjar sprida sig från prostatan till övriga delar av kroppenIntroduction: Prostate cancer is the most common cancer type among men in Sweden. The malignant growth is normally a slow process and most patients are diagnosed at an age of 70 or more. However, some are subjected to a more aggressive form that requires an early diagnose to enhance the chances to overcome the disease. By combining monoclonal antibodies (mAbs) against two proteins connected with p

Background: Data from 1998 showed that CT represents about 10% of all the diagnostic X-ray examinations and almost 70% of the total radiation dose from medical diagnostic examinations in Sweden. Because of this there is a strong need to minimize the radiation dose and adapt the dose to each patient’s examination area and anatomy. Today practically all-modern CT systems are delivered with automatic

I en linjäraccelerator som används för strålterapi överförs konventionellt energi till elektroner som skickas i en stråle mot en metallplatta. Då elektronerna snabbt bromsas upp i plattan utsänds fotoner med hög energi i olika riktningar, men i största mån rakt framåt. Den breda fotonstråle som skapas bländas sedan in till önskade dimensioner av flyttbara blyblock i acceleratorhuvudet. Strålen är "Introduction For IMRT treatments, removing the flattening filter could be beneficial, as it would decrease the beam-on time required for delivering a certain dose. The aim of this work has been to assess the calculation accuracy obtained when implementing flattening filter free beam data into the treatment planning system Oncentra MasterPlan. Methods An Elekta Precise medical linear accele

In an emergency situation where radioactive material has been spread to the environment and large groups of people have been internally contaminated there is a need for rapid examination of the activity contents in those persons. The specific purpose of this work is to explore methods for rapid in-vivo determination of 60Co in humans using equipments not dedicated to whole-body counting, in order

Vid folksjukdomar som stroke, cancer och demens kan det kapillära blodflödet (perfusionen) i hjärnan påverkas. Genom att studera blodflödet ökar möjligheten att ställa rätt diagnos och i vissa fall kan även behandlingseffekt bedömas via ändringar i blodflödet Med en metod som kallas "dynamic susceptibility contrast magnetic resonance imaging" (DSC-MRI) kan blodflödet mätas med magnetkameIntroductionThe perfusion-related parameters cerebral blood flow (CBF) and cerebral blood volume (CBV) can be measured using dynamic susceptibility-contrast magnetic resonance imaging (DSC-MRI). However, absolute values of CBF and CBV are often overestimated and quantification of these parameters is challenging. By acquiring an independent absolute CBV estimate, a calibration factor can be obtaine

Purpose: The purpose of this work was to explore the possibility to compare treatment-planning- and treatment-delivery systems for intensity modulated radiation therapy (IMRT) using an objective approach. The approach investigated was the Pareto front concept. An additional aim was to adequately compare three different IMRT treatment planning and delivery systemsMaterials and methods: In IMRT trea

ntensity modulated radiation therapy (IMRT) is becoming a more and moreused technique in radiation therapy. The main reason for this is that IMRT treament delivers a more conformal dose to the target together with a better sparing of organs at risk. Quality assurance of the generated IMRT treatment plan is of most importance to ensure that the patient recives the planned dose. Different methods ex

Introduction: SharePlanTM is a new type of treatment planning system produced by RaySearch Laboratories AB for TomoTherapy Inc. SharePlan enables transfer of treatment plans generated with the TomoTherapy Hi∙Art® system to plans deliverable at conventional linacs. The main reason for this is to ensure continuous patient treatment if the TomoTherapy unit “goes down”, e.g. at clinics with only one T

Introduction: Regional and global brain volumes are of great interest in many different research projects, not least in Alzheimer’s research. The purpose of this project is to optimize the MPRAGE sequence for automatic and repeatable segmentation of human brain tissue. The volume is calculated for the whole brain, white matter (WM), grey matter (GM) and cerebrospinal fluid (CSF). Materials and met

Introduction; The aim of this study was to examine the possibilities for MRI-based radiotherapy treatment planning. The work included evaluation of geometric image distortions in MR-images, investigations of how segmentation of bone could be performed from images acquired with the ultra short time of echo (UTE) pulse sequence and assessment of dosimetric differences between treatment planning base

Purpose: Radiotherapy of moving tumours is a great challenge in cancer treatment. The moving target will lead to “dose-smearing” of the planned dose distribution and a need for larger margins. To reduce the dose to the surrounding healthy tissue, while still ensuring full coverage of the target, other methods for motion compensation is needed. Inversely optimised arc radiotherapy, where the treatm

Jag har i detta arbete tagit fram en metod för att mäta mängden fett i muskelceller som vare sig kräver vävnadsprover eller nålstick. Metoden ger också en bild av fettfördelningen i vävnaden. Detta kan vara mycket användbart vid utveckling av läkemedel, men också vid diabetes- och fetmaforskning. Muskelceller innehåller ett bränsleförråd i form av en droppe fett. För diabetespatienter och som en b"Introduction Cardiac steatosis, or overstorage of fat in the cardiac muscle cells, is a possible side effect from drugs treating diabetes mellitus. Therefore, a non-invasive means of fat quantification is needed during drug development. The aim of this master thesis is to develop a method to quantify the fraction intra-myocellular fat in the cardiac muscle of rats using magnetic resonance im

En ofta använd behandlingsmetod mot cancer är strålbehandling. Inför en sådan behandling undersöks patienten ofta med en typ av röntgenundersökning som kallas datortomografi (eng. computed tomomgraphy, CT). Röntgenbilderna visar hur mycket av strålningen som absorberas av kroppen, vilket innebär att man tydligt ser skillnad mellan ben, som absorberar mer av strålningen än vävnad och luft, som strå"Introduction; The aim of this study was to examine the possibilities for MRI-based radiotherapy treatment planning. The work included evaluation of geometric image distortions in MR-images, investigations of how segmentation of bone could be performed from images acquired with the ultra short time of echo (UTE) pulse sequence and assessment of dosimetric differences between treatment plannin

Monte Carlo-simuleringar har fått en ökad betydelse som forskningsverktyg inom nuklearmedicinsk bildgivning eftersom man på ett mycket kontrollerat sätt kan studera nästan vad man vill. I denna studie har datorsimuleringar av ett PET-system gjorts med ett program som heter GATE. PET (Positron Emission Tomography) är en nuklearmedicinsk bildgivningsteknik som används mer och mer inom sjukvården sIntroduction: Monte Carlo simulation is a powerful tool in research in the field of nuclear medicine imaging and there is a wide area of applications. The purpose of this work was (1) to understand the basics of the Monte Carlo simulation software Geant4 Application for Tomographic Emission (GATE); (2) to create a model of Philips Gemini TF PET/CT system; (3) to run a number of simulations to comp

En vanlig typ av behandling vid cancer är strålbehandling. Tekniken har utvecklats mycket de senaste åren och med ny teknik kommer bättre behandlingsresultat och bättre skydd mot strålningen. När det är dags att byta ut en äldre behandlingsteknik mot en nyare är det en del faktorer som måste undersökas. Detta arbete undersöker just de möjligheterna vid en ny typ av behandling för läppcancer. StrIntroduction: From 1988 – 2004, patients with squamous cell carcinoma in the lower lip were treated with medium dose rate (MDR) 192Ir wires using a manual afterloading tech-nique. An average of 3 wires were used, each with a mean length of 36 mm (range 27 – 65 mm) and a mean dose rate of 4.5 Gy/h (range 1.8 – 8.7 Gy/h). The average prescribed dose was 21.5 Gy (range 21.0 – 32.6 Gy) at the 85% isod

Idag finns det många olika sätt att avbilda människokroppens inre. Två av de vanligaste metoderna som används idag är magnetresonans (MR) och datortomografi (CT). MR använder sig av starka magnetfält och radiovågor för att skapa snittbilder av kroppen, medan CT använder sig av röntgenstrålar. Båda kamerorna har sina fördelar och nackdelar. MR ger bättre vävnadskontrast, det vill säga det är lättarIntroduction MRI provides better soft tissue contrast than CT and is an invaluable tool in the radiotherapy treatment process. The gold standard today is image fusion of MRI and CT data where targets and organs-at-risk are delineated on the MRI data and the dose calculation is performed on the CT data. It is appealing to exclude CT from the process in order to reduce cost and time and to eliminate

Uppsatsen undersöker hur Jan Myrdal arbetar med satiren som metod i romanen Jubelvår, med utgångspunkt i dess förhållande till den groteska realismen och några av de klassiska 1700-talssatirerna.

Many European countries have recently decided to increase their statutory retirement ages because the demographic change poses a challenge to the stability of social security systems. The success of this policy depends among others on the health effect of such a delayed retirement. This study analyzes the effect of retirement on mental and physical health and further examines whether the health ef