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Vattenmolekyler är i ständig slumpmässig rörelse som beror på systemets termisk energi, dvs temperaturen. Diffusionsrörelsen kallas även Brownsk rörelse efter den engelske botanikerns Brown, som upptäckte fenomenet på 1800 talet. Människokroppen består till 70 % av vatten, vilket gör det lämpligt att använda MRT för att studera diffusionsegenskaper i biologisk vävnad och för klinisk diagnostik av Magnetic resonance imaging (MRI) is still a fast growing area of research and is an important part of the clinical tools used for diagnosis of various diseases. The diagnostic values of diffusion imaging are well known especially for ischemic stroke in the acute phase. This work concerns whether the apparent diffusion coefficient (ADC) and the full width at half maximum (FWHM) changes when the ima

Small-animal positron emission tomography (PET) has proven to be a promising and useful modality for preclinical pharmacokinetic studies. Thanks to high sensitivity and spatial resolution in the range of a few millimetres, the possibility to perform reliable and accurate quantification and absorbed dose estimates is within reach. In preclinical radioimmunotherapy (RIT), the slow targeting and clea

"Diffusion magnetic resonance imaging (MRI) is today a well-established method in clinics around the world. For example it is a leading method or diagnosing ischaemic stroke at an early stage. Trough research it is a continuously growing field applicable to many different tasks. Alternatively, the diffusion MRI can be used for morphologic studies by the use of q-space analysis. q-space imag

Vid strålbehandling används olika typer av strålning beroende på vad man ska behandla. Mätningarna i min undersökning gjordes på joniserande strålning med låg energi jämfört med den typ man vanligtvis förknippar med strålbehandling. Den sortens strålning som jag mätte på används främst vid behandling av åkommor som är relativt ytliga, till exempel hudcancer eller psoriasis. Läkarna ordinerar hur sAbsorbed dose was determined under reference conditions at four x-ray qualities; 30, 80, 120 and 200 kV using five different dosimetry protocols and codes of practice; IAEA TRS-398, AAPM, IPEMB, NCS and DIN. The dose determined by the IAEA protocol was chosen as reference. The dosimetry protocols use different formalisms for determining the absolute dose in a reference point. The IAEA and DIN prot

Varje år diagnostiseras i Sverige ungefär 1100 personer med cancer i huvudhalsregionen. Typiska diagnoser är tungcancer, läppcancer och cancer i struphuvudet. I och runt om munhålan finns det stora skillnader i densitet mellan till exempel vävnad och tänder och vävnad och tandlagningar. I detta arbete så har effekterna av ett antal olika tandlagningsmaterial på dosberäkningarna undersökts. För a"Introduction: Around 1.000 people are diagnosed with head and neck cancer in Sweden every year. Radiotherapy is often used to treat these tumors. When irradiating patients in the head and neck area there are some problems. One of these problems is the large difference in density between the oral tissue and dental materials. Another problem is the image artifacts due to high-density materials

Inom kärnkraftsverken, läkemedelsindustrin, biotekniklaboratorier mfl är det vanligt att det radioaktiva ämnet 14C förekommer i olika former. Inom kärnkraftsverken som en biprodukt vid elproduktion och inom läkemedelsindustrin används det som markör för att studera hur sunbstansen distribueras i kroppen. Genom inandning vid t ex oförsiktighet kan de människor som arbetar med dessa olika substanserWith the help from accelerator mass spectrometry (AMS), hair from workers within the nuclear power industry, pharmaceutical and biotechnology industry has been investigated to see if contamination from 14C. 14C-using companies and nuclear power plants were contacted, volunteers were recruited, who sent in hair samples together with a questionnaire. The samples were washed and prepared for 14C anal

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