Sökning: "radiofysik"

Visar resultat 1 - 5 av 69 avhandlingar innehållade ordet radiofysik.

  1. 1. Quality assurance for magnetic resonance imaging (MRI) in radiotherapy

    Detta är en avhandling från Umeå : Department of radiation sciences, Umeå university

    Författare :Mary Adjeiwaah; Tufve Nyholm; Rob HN Tijssen; [2017]
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Magnetic resonance imaging; Radiotherapy; geometric distortions; patient-induced susceptibilities MR-only; radiofysik; radiation physics;

    Sammanfattning : Magnetic resonance imaging (MRI) utilizes the magnetic properties of tissues to generate image-forming signals. MRI has exquisite soft-tissue contrast and since tumors are mainly soft-tissues, it offers improved delineation of the target volume and nearby organs at risk. LÄS MER

  2. 2. Ion recombination in liquid ionization chambers development of an experimental method to quantify general recombination

    Detta är en avhandling från Umeå : Umeå universitet

    Författare :Jonas Andersson; Heikki Tölli; Lennart Johansson; Anders Ahnesjö; [2013]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; General recombination; initial recombination; liquid ionization chamber; radiation dosimetry; radiofysik; radiation physics;

    Sammanfattning : An experimental method (the two-dose-rate method) for the correction of general recombination losses in liquid ionization chambers has been developed and employed in experiments with different liquids and radiation qualities. The method is based on a disassociation of initial and general recombination, since an ionized liquid is simultaneously affected by both of these processes. LÄS MER

  3. 3. Applications of statistical methods in quantitative magnetic resonance imaging

    Detta är en avhandling från Umeå : Umeå universitet

    Författare :Patrik Brynolfsson; Anders Garpebring; Tufve Nyholm; Eirik Malinen; [2017]
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Quantitative imaging; tumor imaging; dynamic contrast-enhanced MRI; diffusion weighted MRI; texture analysis; radiofysik; radiation physics;

    Sammanfattning : Magnetic resonance imaging, MRI, offers a vast range of imaging methods that can be employed in the characterization of tumors. MRI is generally used in a qualitative way, where radiologists interpret the images for e.g. diagnosis, follow ups, or assessment of treatment response. LÄS MER

  4. 4. Contributions to quantitative dynamic contrast-enhanced MRI

    Detta är en avhandling från Umeå : Umeå Universitet

    Författare :Anders Garpebring; Mikael Karlsson; Ronnie Wirestam; Nils Östlund; Jón Hauksson; Steven Sourbron; [2011]
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Dynamic contrast-enhanced MRI; quantitative imaging; parameter estimation; uncertainty estimation; arterial input function; radiofysik; radiation physics;

    Sammanfattning : Background: Dynamic contrast-enhanced MRI (DCE-MRI) has the potential to produce images of physiological quantities such as blood flow, blood vessel volume fraction, and blood vessel permeability. Such information is highly valuable, e.g., in oncology. LÄS MER

  5. 5. Magnetic resonance imaging with ultrashort echo time as a substitute for X-ray computed tomography

    Detta är en avhandling från Umeå : Umeå universitet

    Författare :Adam Johansson; Tufve Nyholm; Karlsson Mikael; James Balter; [2014]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; magnetic resonance imaging; computed tomography substitute; ultrashort echo time; parallel imaging; radial imaging; radiofysik; radiation physics;

    Sammanfattning : Radiotherapy dose calculations have evolved from simple factor based methods performed with pen and paper, into computationally intensive simulations based on Monte Carlo theory and energy deposition kernel convolution.Similarly, in the field of positron emission tomography (PET), attenuation correction, which was originally omitted entirely, is now a crucial component of any PET reconstruction algorithm. LÄS MER