Sökning: "radiofysik"

Visar resultat 36 - 40 av 106 avhandlingar innehållade ordet radiofysik.

  1. 36. Fast neutron dosimetry : a study of basic dosimetric properties of fast-neutrons for external beam radiotherapy and problems associated with corrections of measured charged particle cross-sections

    Författare :Jonas Söderberg; Lennart Lindborg; Linköpings universitet; []
    Nyckelord :MEDICINE; MEDICIN;

    Sammanfattning : Basic dosimetric properties of fast-neutron beams with energies ≤80 MeV were explored using Monte Carlo techniques. Elementary pencil-beam dose distributions taking into account transport of all relevant types of released charged particles (protons, deuterons, tritons, 3He and a particles) were calculated and used to derive several absorbed dose distributions. LÄS MER

  3. 37. Cerebral arterial pulsatility imaging using 4D flow MRI : methodological development and applications in brain aging

    Författare :Tomas Vikner; Anders Wåhlin; Anders Eklund; Jan Malm; Lars Nyberg; Susanne Schnell; Umeå universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Magnetic resonance imaging; 4D flow MRI; medical image analysis; cerebral hemodynamics; arterial pulsatility; DCE MRI; blood-brain barrier; white matter lesions; perivascular spaces; cerebral small vessel disease; hippocampus; cognition; aging; biomedicinsk strålningsvetenskap; Biomedical Radiation Science;

    Sammanfattning : 4D flow magnetic resonance imaging (MRI) is increasingly recognizedas a versatile tool to assess arterial and venous hemodynamics. Cerebral arterial pulsatility is typically assessed by analyzing flow waveforms over the cardiac cycle, where flow amplitude is a function of cardiac output, central arterial stiffness, and cerebrovascular resistance and compliance. LÄS MER

  4. 38. Cerebral blood flow distribution, collateral function and pulsatility in healthy and in patients with symptomatic carotid stenosis  : a magnetic resonance imaging approach

    Författare :Laleh Zarrinkoob; Jan Malm; Anders Eklund; Khalid Ambarki; Sepideh Amin-Hanjani; Umeå universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Aging; Arterial pulsatility; Carotid stenosis; Cerebral arteries; Cerebral blood flow; Cerebral collateral blood flow; Circle of Willis; Phase contrast magnetic resonance imaging;

    Sammanfattning : Background: For the detection and treatment of early cerebral vascular disease it is of paramount importance to first understand the normal physiology of the cerebral vasculature, and subsequently, to understand how and when pathology can develop from that. This is especially important as the population above 65 years of age is increasing and aging itself is an established risk factor for the development of cerebral vascular disease. LÄS MER

  5. 39. Dosimetry Studies of Different Radiotherapy Applications using Monte Carlo Radiation Transport Calculations

    Författare :Shirin Abbasinejad Enger; Hans Lundqvist; Anders Ahnesjö; Irena Gudowska; Uppsala universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; External Beam Radiotherapy; Gadolinium Neutron Capture Therapy; Gadolinium Neutron Capture Brachytherapy; Targeted Radionuclide therapy; Detector Response Modelling; Monte Carlo Simulation.; Radiological physics; Radiofysik;

    Sammanfattning : Developing radiation delivery systems for optimisation of absorbed dose to the target without normal tissue toxicity requires advanced calculations for transport of radiation. In this thesis absorbed dose and fluence in different radiotherapy applications were calculated by using Monte Carlo (MC) simulations. LÄS MER

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

    Författare :Mary Adjeiwaah; Tufve Nyholm; Rob HN Tijssen; Umeå universitet; []
    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