Browsing NTNU Open by Author "Waaler, Dag"
Now showing items 1-14 of 14
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A Weighted Histogram-Based Tone Mapping Algorithm for CT images
Völgyes, David; Martinsen, Anne Catrine Trægde; Stray-Pedersen, Arne; Waaler, Dag; Pedersen, Marius (Journal article; Peer reviewed, 2018)Computed Tomography (CT) images have a high dynamic range, which makes visualization challenging. Histogram equalization methods either use spatially invariant weights or limited kernel size due to the complexity of pairwise ... -
Applicability of a clinical cardiac CT protocol in post mortem studies
Völgyes, David; Pedersen, Marius; Stray-Pedersen, Arne; Waaler, Dag; Martinsen, Anne Catrine Trægde (Journal article; Peer reviewed, 2018)Objective Confirmation whether an optimized clinical cardiac CT scan protocol is also optimal for post mortem cardiac CT scans without iodine contrast or the reconstruction parameters should be changed. Materials ... -
Evaluation of color spaces for unsupervised and deep learning skin lesion segmentation
Osadebey, Michael; Pedersen, Marius; Waaler, Dag (Chapter, 2020)The reliability of skin cancer diagnosis is dependent on accurate lesion segmentation. The choice of a color space in most contributions on skin lesion segmentation for melanoma detection are based on qualitative rather ... -
How different iterative and filtered back projection kernels affect CT numbers and low contrast detectability
Volgyes, David; Pedersen, Marius; Stray-Pedersen, Arne; Waaler, Dag; Martinsen, Anne Catrine Trægde (Journal article; Peer reviewed, 2016)Objective: The aim of this study was to evaluate how different iterative and filtered back projection kernels affect the computed tomography (CT) numbers and low contrast detectability. Methods: Five different scans ... -
How radiographers visually perceive X-ray images with the task of accepting or rejecting them – a pilot study
Waaler, Dag; Hammer, Sigrid; Langdalen, Camilla Carlsson; Haug, Linn Therese Håkonsen (Journal article; Peer reviewed, 2017)Introduction: Radiographer´s usual role in the medical imaging chain is to acquire relevant and qualitatively good images that help the radiologist or physician to diagnose most accurately. After the image acquisition, the ... -
Hvilken erfaring har radiologisk personell med radiografer som har videreutdanning i beskrivelse og tolkning av skjelettbilder?
Andersen, Karen-Sofie; Bergersen, Ingrid Helene (Bachelor thesis, 2019)Problemstilling: «Hvilken erfaring har radiologisk personell med radiografer som har videreutdanning i beskrivelse og tolkning av skjelettbilder?» Hensikt: Hensikten med denne oppgaven var å undersøke hvilke erfaringer ... -
Image De-Quantization Using Plate Bending Model
Völgyes, David; Martinsen, Anne Catrine Trægde; Stray-Pedersen, Arne; Waaler, Dag; Pedersen, Marius (Journal article; Peer reviewed, 2018)Discretized image signals might have a lower dynamic range than the display. Because of this, false contours might appear when the image has the same pixel value for a larger region and the distance between pixel levels ... -
Image quality in forensic CT imaging
Völgyes, David (Doctoral theses at NTNU;2018:294, Doctoral thesis, 2018)What factors affect the diagnostic image quality in forensic computed tomography (CT) imaging? In this thesis I briefly present the main steps from CT scanning to diagnostics. The thesis is built on four core papers. The ... -
Image texture and radiation dose properties in CT
Możejko, Dawid; Andersen, Hilde Kjernlie; Pedersen, Marius; Waaler, Dag; Martinsen, Anne Catrine Trægde (Journal article; Peer reviewed, 2016)The aim of this study was to compare image noise properties of GE Discovery HD 750 and Toshiba Aquilion ONE. The uniformity section of a Catphan 600 image quality assurance phantom was scanned with both scanners, at different ... -
Influence of adaptive statistical iterative reconstruction algorithm on image quality in coronary computed tomography angiography
Precht, Helle; Thygesen, Jesper; Gerke, Oke; Egstrup, Kenneth; Waaler, Dag; Lambrechtsen, Jess (Peer reviewed; Journal article, 2016)Background Coronary computed tomography angiography (CCTA) requires high spatial and temporal resolution, increased low contrast resolution for the assessment of coronary artery stenosis, plaque detection, and/or ... -
Learning-based segmentation of optic disc in retinal images using clustering trees and local mode filtering
Osadebey, Michael; Pedersen, Marius; Waaler, Dag (Chapter, 2020)Delineation of the optic disc boundary in retinal images is the first step towards the computation of cup-to-disc ratio, an important indicator of ophthalmic pathologies such as glaucoma. This paper proposes the combination ... -
Memory Effects in Subjective Quality Assessment of X-Ray Images
Landré, Victor; Pedersen, Marius; Waaler, Dag (Chapter; Conference object; Peer reviewed, 2017)Experiments with human observers is considered as the most precise way for the assessment of image quality. Although widely used, such experiments have its pitfalls and hazards. In this work we investigate if the quality ... -
Plant Leaves Region Segmentation in Cluttered and Occluded Images Using Perceptual Color Space and K-means-Derived Threshold with Set Theory
Osadebey, Michael; Pedersen, Marius; Waaler, Dag (Journal article; Peer reviewed, 2019) -
Tegn på fysisk barnemishandling på en konvensjonell røntgenlab
Hollekim, Ida; Arntzen, Marit; Holen, Miriam Myrum (Bachelor thesis, 2019)Problemstilling: Hvilke fysiske tegn gir grunnlag for at en radiograf kan mistenke fysisk barnemishandling på en konvensjonell røntgen-lab? Hensikt: Hensikten med å skrive denne oppgaven er å øke kunnskapen om barnemishandling ...