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  • Public defence: 2018-03-09 09:30 Örebro universitet, Campus USÖ, hörsal C3, Örebro
    Andersson, Karin
    Örebro University, School of Medical Sciences.
    Metal artifacts in computed tomography: impact of reduction methods on image quality and radiotherapy treatment planning2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Degradation of image quality by metal artifacts is a common problem in computed tomography (CT) imaging, which can limit the diagnostic value of a CT examination and also introduce inaccuracies in radiotherapy (RT) treatment planning. In recent years, commercial metal artifact reduction (MAR) methods have been launched by several CT vendors. The overall aim of this thesis was to evaluate MAR methods in diagnostic imaging and RT treatment planning.

    Evaluations of hip prosthesis phantom CT images showed that MAR algorithms in general improved image quality, based on both visual grading analysis and quantitative measures, while the application of virtual monoenergetic reconstructions insufficiently reduced metal artifacts. In some cases additional artifacts were introduced by the MAR algorithms. MAR algorithms were also evaluated in hip prosthesis phantom CT imaging used for proton therapy treatment planning, where improvements in dose calculation accuracy were observed.

    Studies of Head & Neck (H&N) implant CT images in RT treatment planning were also performed. By visual grading of anatomy visualization with respect to target delineation in dental implant patient images, MAR algorithms were shown to significantly improve image quality. However, only minor effects of H&N implant artifacts on proton dose distributions were seen. The impact might be greater for more severe artifacts than those studied here, and thus further investigations of such cases are needed.

    In conclusion, MAR algorithms have been shown to enhance image quality for diagnostic applications and to improve anatomy visualization in RT treatment planning. The MAR algorithms led to increased proton dose calculation accuracy in some cases, while in other situations only minor changes were seen.

    List of papers
    1. Evaluation of a metal artifact reduction algorithm in CT studies used for proton radiotherapy treatment planning
    Open this publication in new window or tab >>Evaluation of a metal artifact reduction algorithm in CT studies used for proton radiotherapy treatment planning
    2014 (English)In: Journal of Applied Clinical Medical Physics, ISSN 1526-9914, E-ISSN 1526-9914, Vol. 15, no 5, p. 112-119Article in journal (Refereed) Published
    Abstract [en]

    Metal objects in the body such as hip prostheses cause artifacts in CT images. When CT images degraded by artifacts are used for treatment planning of radiotherapy, the artifacts can yield inaccurate dose calculations and, for particle beams, erroneous penetration depths. A metal artifact reduction software (O-MAR) installed on a Philips Brilliance Big Bore CT has been tested for applications in treatment planning of proton radiotherapy. Hip prostheses mounted in a water phantom were used as test objects. Images without metal objects were acquired and used as reference data for the analysis of artifact-affected regions outside of the metal objects in both the O-MAR corrected and the uncorrected images. Water equivalent thicknesses (WET) based on proton stopping power data were calculated to quantify differences in the calculated proton beam penetration for the different image sets. The WET to a selected point of interest between the hip prostheses was calculated for several beam directions of clinical relevance. The results show that the calculated differences in WET relative to the reference case were decreased when the O-MAR algorithm was applied. WET differences up to 2.0 cm were seen in the uncorrected case while, for the O-MAR corrected case, the maximum difference was decreased to 0.4 cm. The O-MAR algorithm can significantly improve the accuracy in proton range calculations. However, there are some residual effects, and the use of proton beam directions along artifact streaks should only be used with caution and appropriate margins.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2014
    Keyword
    metal artifact reduction, radiation therapy, water equivalent thickness, proton range
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:oru:diva-65011 (URN)10.1120/jacmp.v15i5.4857 (DOI)000345121900010 ()28297224 (PubMedID)2-s2.0-84929502869 (Scopus ID)
    Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-02-15Bibliographically approved
    2. Metal artefact reduction in CT imaging of hip prostheses-an evaluation of commercial techniques provided by four vendors
    Open this publication in new window or tab >>Metal artefact reduction in CT imaging of hip prostheses-an evaluation of commercial techniques provided by four vendors
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    2015 (English)In: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 88, no 1052, article id 20140473Article in journal (Refereed) Published
    Abstract [en]

    Objective: The aim of this study was to evaluate commercial metal artefact reduction (MAR) techniques in X-ray CT imaging of hip prostheses.

    Methods: Monoenergetic reconstructions of dual-energy CT (DECT) data and several different MAR algorithms, combined with single-energy CT or DECT, were evaluated by imaging a bilateral hip prosthesis phantom. The MAR images were compared with uncorrected images based on CT number accuracy and noise in different regions of interest.

    Results: The three MAR algorithms studied implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to the prostheses and between the two prostheses. The application of monoenergetic reconstruction, without any MAR algorithm, did not decrease the noise in the regions close to the prostheses to the same extent as did the MAR algorithms and even increased the noise in the region between the prostheses.

    Conclusion: The MAR algorithms evaluated generally improved CT number accuracy and substantially reduced the noise in the hip prostheses phantom images, both close to the prostheses and between the two prostheses. The study showed that the monoenergetic reconstructions evaluated did not sufficiently reduce the severe metal artefact caused by large orthopaedic implants.

    Advances in knowledge: This study evaluates several commercially available MAR techniques in CT imaging of large orthopaedic implants.

    Place, publisher, year, edition, pages
    British Institute of Radiology, 2015
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Radiology
    Identifiers
    urn:nbn:se:oru:diva-46510 (URN)10.1259/bjr.20140473 (DOI)000363313000002 ()26110201 (PubMedID)2-s2.0-84938837932 (Scopus ID)
    Available from: 2015-11-17 Created: 2015-11-16 Last updated: 2018-02-15Bibliographically approved
    3. Visual grading evaluation of commercially available metal artefact reduction techniques in hip prosthesis computed tomography
    Open this publication in new window or tab >>Visual grading evaluation of commercially available metal artefact reduction techniques in hip prosthesis computed tomography
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    2016 (English)In: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 89, no 1063, article id 20150993Article in journal (Refereed) Published
    Abstract [en]

    Objectives: To evaluate metal artefact reduction (MAR) techniques from four computed tomography (CT) vendors in hip prosthesis imaging.

    Methods: Bilateral hip prosthesis phantom images, obtained by using MAR algorithms for single energy CT data or dual energy CT (DECT) data and by monoenergetic reconstructions of DECT data, were visually graded by five radiologists using ten image quality criteria. Comparisons between the MAR images and a reference image were performed for each scanner separately. Ordinal probit regression analysis was used.

    Results: The MAR algorithms in general improved the image quality based on the majority of the criteria (up to between 8/10 and 10/10) with a statistically improvement in overall image quality (P<0.001). However, degradation of image quality, such as new artefacts, was seen in some cases. A few monoenergetic reconstruction series improved the image quality (P<0.004) for one of the DECT scanners, but it was only improved for some of the criteria (up to 5/10). Monoenergetic reconstructions resulted in worse image quality for the majority of the criteria (up to 7/10) for the other DECT scanner.

    Conclusions: The MAR algorithms improved the image quality of the hip prosthesis CT images. However, since additional artefacts and degradation of image quality were seen in some cases, all algorithms should be carefully evaluated for every clinical situation. Monoenergetic reconstructions were in general concluded to be insufficient for reducing metal artifacts. Advances in knowledge: Qualitative evaluation of the usefulness of several MAR techniques from different vendors in CT imaging of hip prosthesis.

    Place, publisher, year, edition, pages
    London, United Kingdom: British Institute of Radiology, 2016
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Radiology
    Identifiers
    urn:nbn:se:oru:diva-50103 (URN)10.1259/bjr.20150993 (DOI)000378096400009 ()27123700 (PubMedID)
    Available from: 2016-05-03 Created: 2016-05-03 Last updated: 2018-02-15Bibliographically approved
    4. CT image metal artifacts in proton radiotherapy treatment planning: evaluation of two commercial correction algorithms
    Open this publication in new window or tab >>CT image metal artifacts in proton radiotherapy treatment planning: evaluation of two commercial correction algorithms
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    (English)Manuscript (preprint) (Other academic)
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:oru:diva-65012 (URN)
    Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-02-15Bibliographically approved
  • Public defence: 2018-03-09 10:00 Örebro universitet, Prismahuset, Hörsal 1, Örebro
    Skagerstrand, Åsa
    Örebro University, School of Health Sciences.
    Perception of disturbing sounds: Investigations of people with hearing loss and normal hearing2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present thesis concerns the daily sound environment and the human perception of the same. The sound environment affects the possibility to be active in a communication. With background noise, it may be harder to hear desired signals, and when suffering from a hearing loss, negative effects of the background noise increase. Previous research has explored, that persons with hearing loss benefit from hearing aid usage, but there is a risk of non-usage due to low sound quality. The non-usage of hearing aids has furthermore been described as a cause of isolation and social withdrawal for persons with hearing loss.

    The general aim of the present thesis is to explore the concept of disturbing sounds in a daily sound environment and to examine the influence of hearing loss and hearing aid usage. Disturbing sounds were investigated in means of perception of loudness and annoyance, where loudness concerned the acoustical properties, mainly sound level, whereas annoyance concerned the psychological phenomenon, defined as an individual adverse reaction to noise. The results of studies I and II showed, that hearing aid users experience disturbing sounds more or less daily, and that those sounds resulted in a decreased usage of hearing aids. The effect of disturbing sounds seemed to rely on several factors, acoustical as well as psychological, and there was not one single factor providing a full explanation of disturbance. In study III and IV, the perception of sounds in normal hearing and hearing impaired persons were thoroughly examined and revealed that hearing thresholds affect the perceived loudness and annoyance. Furthermore, the effect of hearing aids on loudness and annoyance perception was investigated. The results showed that hearing aids restored the loudness and annoyance to levels comparable to people with normal hearing function. The results of the studies stress that additional research should focus on the implementation of knowledge of disturbing sounds in audiological rehabilitation, in order to increase the benefit of hearing aid usage.

    List of papers
    1. Sounds perceived as annoying by hearing-aid users in their daily soundscape
    Open this publication in new window or tab >>Sounds perceived as annoying by hearing-aid users in their daily soundscape
    2014 (English)In: International Journal of Audiology, ISSN 1499-2027, E-ISSN 1708-8186, Vol. 53, no 4, p. 259-269Article in journal (Refereed) Published
    Abstract [en]

    Background: The noises in modern soundscapes continue to increase and are a major origin for annoyance. For a hearing-impaired person, a hearing aid is often beneficial, but noise and annoying sounds can result in non-use of the hearing aid, temporary or permanently.

    Objective: The purpose of this study was to identify annoying sounds in a daily soundscape for hearing-aid users.

    Design: A diary was used to collect data where the participants answered four questions per day about annoying sounds in the daily soundscape over a two-week period.

    Study sample: Sixty adult hearing-aid users. Results: Of the 60 participants 91% experienced annoying sounds daily when using hearing aids. The annoying sound mentioned by most users, was verbal human sounds, followed by other daily sound sources categorized into 17 groups such as TV/radio, vehicles, and machine tools. When the hearing-aid users were grouped in relation to age, hearing loss, gender, hearing-aid experience, and type of signal processing used in their hearing aids, small and only few significant differences were found when comparing their experience of annoying sounds.

    Conclusions: The results indicate that hearing-aid users often experience annoying sounds and improved clinical fitting routines may reduce the problem.

    Place, publisher, year, edition, pages
    London: Informa Healthcare, 2014
    Keyword
    Soundscape, annoying sounds, hearing aid, hearing-aid fitting
    National Category
    Otorhinolaryngology
    Identifiers
    urn:nbn:se:oru:diva-34849 (URN)10.3109/14992027.2013.876108 (DOI)000332867100007 ()24495276 (PubMedID)2-s2.0-84896353214 (Scopus ID)
    Available from: 2014-04-28 Created: 2014-04-25 Last updated: 2018-02-15Bibliographically approved
    2. Acoustic analysis of real-life sounds that affect hearing aid usage
    Open this publication in new window or tab >>Acoustic analysis of real-life sounds that affect hearing aid usage
    (English)Manuscript (preprint) (Other academic)
    National Category
    Other Health Sciences
    Research subject
    Disability Science
    Identifiers
    urn:nbn:se:oru:diva-65013 (URN)
    Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-02-15Bibliographically approved
    3. Loudness and annoyance of disturbing sounds: perception by normal hearing subjects
    Open this publication in new window or tab >>Loudness and annoyance of disturbing sounds: perception by normal hearing subjects
    2017 (English)In: International Journal of Audiology, ISSN 1499-2027, E-ISSN 1708-8186, Vol. 56, no 10, p. 775-783Article in journal (Refereed) Published
    Abstract [en]

    OBJECTIVE: Sounds in the daily environment may cause loudness and annoyance. The present study investigated the perception of loudness and annoyance for eight different sounds present in a daily sound environment and at nine different levels varying by ±20 dB around the recorded level. The outcomes were related to tests of participants' auditory and cognitive abilities.

    DESIGN: The participants undertook auditory and working memory (WM) tests prior to ratings of everyday sounds previously shown to be disturbing for persons with hearing impairment (hearing aid users).

    STUDY SAMPLE: Twenty-one participants aged between 24 and 71 years, with normal hearing threshold levels.

    RESULTS: Both perceived loudness and annoyance were primarily driven by the sound level. Sounds emitted from paper were rated as having greater loudness and being more annoying than the other sound sources at the same sound level. Auditory and cognitive abilities did not influence the perception of loudness and annoyance.

    CONCLUSIONS: Loudness and annoyance ratings were mainly driven by sound level. Expectations of a sound seemed to influence the assessment of loudness and annoyance while auditory performance and WM capacity showed no influence on the ratings.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2017
    Keyword
    Psychoacoustics/hearing science; noise; psycho-social/emotional; behavioural measures
    National Category
    Otorhinolaryngology Other Medical Sciences not elsewhere specified
    Identifiers
    urn:nbn:se:oru:diva-60890 (URN)10.1080/14992027.2017.1321790 (DOI)000416642900009 ()28485649 (PubMedID)2-s2.0-85019114085 (Scopus ID)
    Available from: 2017-09-19 Created: 2017-09-19 Last updated: 2018-02-15Bibliographically approved
    4. Loudness and annoyance of disturbing sounds: Perception by people with hearing loss
    Open this publication in new window or tab >>Loudness and annoyance of disturbing sounds: Perception by people with hearing loss
    (English)Manuscript (preprint) (Other academic)
    National Category
    Other Health Sciences
    Research subject
    Disability Science
    Identifiers
    urn:nbn:se:oru:diva-65014 (URN)
    Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-02-15Bibliographically approved
  • Public defence: 2018-03-16 13:00 Örebro universitet, Campus Grythyttan, Gastronomiska teatern, Grythyttan
    Nilsen, Bente B.
    Örebro University, School of Hospitality, Culinary Arts & Meal Science.
    Growth of schoolchildren: studies on somatic growth and deviant growth patterns such as weight loss and obesity and aspects of intake of breakfast and food items2018Doctoral thesis, comprehensive summary (Other academic)
  • Public defence: 2018-03-16 13:15 Örebro universitet, Forumhuset, Hörsal F, Örebro
    von Schantz, Miriam
    Örebro University, School of Humanities, Education and Social Sciences.
    The Doc, the Mock and the What?: Events of Realing, Mockumentality and the Becoming-Political of the Viewing Subject2018Doctoral thesis, monograph (Other academic)
  • Public defence: 2018-03-23 09:00 Campus USÖ, hörsal C3, Örebro
    Calais, Fredrik
    Örebro University, School of Medical Sciences.
    Coronary artery disease and prognosis in relation to cardiovascularrisk factors, interventional techniques and systemic atherosclerosis2018Doctoral thesis, comprehensive summary (Other academic)
  • Public defence: 2018-03-23 10:00 Örebro universitet, Teknikhuset, Hörsal T, Örebro
    Johannesson, Louise
    Örebro University, Örebro University School of Business.
    Settling disputes at the World Trade Organization2018Doctoral thesis, comprehensive summary (Other academic)
  • Public defence: 2018-03-23 13:15 Örebro universitet, Billbergska huset, Hörsal B, Örebro
    Beime, Kristina S.
    Örebro University, Örebro University School of Business.
    Den avvikande anställda: En studie av den disciplinära processens misslyckande2018Doctoral thesis, monograph (Other academic)
  • Public defence: 2018-04-06 09:00 Campus USÖ, hörsal C3, Örebro
    Meehan, Adrian David
    Örebro University, School of Medical Sciences.
    Lithium - associated hyperparathyroidism: Prevalence, Pathophysiology, Management2018Doctoral thesis, comprehensive summary (Other academic)
  • Public defence: 2018-04-20 09:00 Campus USÖ, hörsal C1, Örebro
    Björkenheim, Anna
    Örebro University, School of Medical Sciences.
    Catheter ablation for atrial fibrillation-effects on rhythm, symptoms and health-related quality of life2018Doctoral thesis, comprehensive summary (Other academic)
  • Public defence: 2018-04-20 13:00 Campus USÖ, hörsal C3, Örebro
    Karefylakis, Christos
    Örebro University, School of Medical Sciences.
    Vitamin D and its role in obesity and other associated conditions2018Doctoral thesis, comprehensive summary (Other academic)
  • Public defence: 2018-06-07 09:15 Campus USÖ, hörsal C3, Örebro
    Arinell, Karin
    Örebro University, School of Medical Sciences.
    Immobilisering som en riskfaktor för arteriella och venösa tromboser2018Doctoral thesis, comprehensive summary (Other academic)