Sökning: "attenuation correction"

Visar resultat 1 - 5 av 25 avhandlingar innehållade orden attenuation correction.

  1. 1. Colour Correction of Underwater Images Using Spectral Data

    Författare :Julia Åhlén; Ewert Bengtsson; Jussi Parkkinen; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Bildanalys; Colour; Correction; Attenuation; Coefficient; Underwater; Bildanalys; Image analysis; Bildanalys; Computer science;

    Sammanfattning : For marine sciences sometimes there is a need to perform underwater photography. Optical properties of light cause severe quality problems for underwater photography. Light of different energies is absorbed at highly different rates under water causing significant bluishness of the images. LÄS MER

  2. 2. Corrections for improved quantitative accuracy in SPECT and planar scintigraphic imaging

    Författare :Anne Larsson; Lennart Johansson; Katrine Åhlström Riklund; Bertil Axelsson; Umeå universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Quantitative SPECT; scintigraphic imaging; attenuation correction; scatter correction; collimator-detector response; septal penetration; background correction; Monte Carlo simulation; Radiological physics; Radiofysik;

    Sammanfattning : A quantitative evaluation of single photon emission computed tomography (SPECT) and planar scintigraphic imaging may be valuable for both diagnostic and therapeutic purposes. For an accurate quantification it is usually necessary to correct for attenuation and scatter and in some cases also for septal penetration. LÄS MER

  3. 3. Assessment of attenuation correction methods for quantitative neuro-PET/MR

    Författare :Joao M. Sousa; Mark Lubberink; Lieuwe Appel; Håkan Ahlström; Mathias Engström; Ivo Rausch; Radiologi Uppsala universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; PET; MRI; attenuation correction; 68Ge transmission; quantification; 11C-PE2I; MRAC; DAT; CBF; Medicinsk radiofysik; Medical Radiophysics;

    Sammanfattning : Hybrid PET/magnetic resonance (MR) can provide physiological, functional, and structural information simultaneously, facilitating research in neurological disorders. For quantitative PET, correction for photon attenuation (AC) is necessary. LÄS MER

  4. 4. Attenuation correction in pulmonary and myocardial single photon emission computed tomography

    Författare :Helén Almquist; Lund Klinisk fysiologi; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Klinisk fysiologi; tomography; medical instrumentation; radiology; Clinical physics; downscatter; myocardial perfustion; ventilation-perfusion ratio; radiologi; pulmonary density; pulmonary perfusion; attenuation correction; SPECT; transmission measurement; tomografi; medicinsk instrumentering;

    Sammanfattning : The objective was to develop and validate methods for single photon emission computed tomography, SPECT, allowing quantitative physiological and diagnostic studies of lung and heart. A method for correction of variable attenuation in SPECT, based on transmission measurements before administration of an isotope to the subject, was developed and evaluated. LÄS MER

  5. 5. Evaluation of attenuation and scatter corrections in lung and brain SPECT

    Författare :Agnetha Gustafsson; Bertil Axelsson; Göteborgs universitet Avdelningen för radiofysik Department of Radiations Physics; []
    Nyckelord :SPECT; attenuation; scatter; detectability; Monte Carlo simulation; MEDICINE; MEDICIN;

    Sammanfattning : Single Photon Emission Computed Tomography (SPECT) is used to image functional processes in the human body. The image process is affected by physical effects such as attenuation, scatter, spatial resolution and statistical noise. LÄS MER