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Coming theses from other universities

  • Climbing up the hearing rehabilitation ladder Author: Elisabeth Ingo Link: Publication date: 2019-08-29 11:49

    Hearing impairment is a major public health problem, affecting communication and participation, and is associated with a range of health problems. Most individuals with perceived hearing impairment do not seek help, do not opt for rehabilitation (hearing aids), and do not use prescribed hearing aids adequately. Reducing the impact of hearing impairment and supporting healthy aging are important public health goals. Motivation, access to hearing health care, and poor societal awareness about hearing impairment, consequences, and rehabilitation options influence help-seeking. Offering online hearing screening has been proposed to improve hearing help-seeking, access to hearing health care, and to increase public knowledge about hearing and hearing impairment. Applying theories from health psychology (i.e. the Stages of change model) could help audiologists and other hearing health care professionals understand the psychological barriers that prevent people with hearing problems to seek help and take up rehabilitation. The overarching aim of this thesis was to investigate behaviors related to hearing rehabilitation (help-seeking, hearing aid uptake, and hearing aid use) in adults who fail an online hearing screening. A second aim was to explore the usefulness of the Stages of change model in predicting hearing rehabilitation related behavior in a self-selected online hearing screening sample. Studies I–IV show tentative support for offering online hearing screening and for supplementary interventions for increasing help-seeking and provide tentative support for Stages of change as a useful classification tool to indicate individual needs for further information and guidance. Future studies should contemplate integrating screening for multiple health-related factors associated with hearing impairment and to provide a clear and tailored pathway for each participant (e.g. referral to adequate health care or equivalent online intervention).

  • Water–fat separation in magnetic resonance imaging and its application in studies of brown adipose tissue Author: Jonathan Andersson Link: Publication date: 2019-08-23 13:12

    Virtually all the magnetic resonance imaging (MRI) signal of a human originates from water and fat molecules. By utilizing the property chemical shift the signal can be separated, creating water- and fat-only images. From these images it is possible to calculate quantitative fat fraction (FF) images, where the value of each voxel is equal to the percentage of its signal originating from fat. In papers I and II methods for water–fat signal separation are presented and evaluated.

    The method in paper I utilizes a graph-cut to separate the signal and was designed to perform well even for a low signal-to-noise ratio (SNR). The method was shown to perform as well as previous methods at high SNRs, and better at low SNRs.

    The method presented in paper II uses convolutional neural networks to perform the signal separation. The method was shown to perform similarly to a previous method using a graph-cut when provided non-undersampled input data. Furthermore, the method was shown to be able to separate the signal using undersampled data. This may allow for accelerated MRI scans in the future.

    Brown adipose tissue (BAT) is a thermogenic organ with the main purpose of expending chemical energy to prevent the body temperature from falling too low. Its energy expending capability makes it a potential target for treating overweight/obesity and metabolic dysfunctions, such as type 2 diabetes. The most well-established way of estimating the metabolic potential of BAT is through measuring glucose uptake using 18F-fludeoxyglucose (18F-FDG) positron emission tomography (PET) during cooling. This technique exposes subjects to potentially harmful ionizing radiation, and alternative methods are desired. One alternative method is measuring the BAT FF using MRI.

    In paper III the BAT FF in 7-year olds was shown to be negatively associated with blood serum levels of the bone-specific protein osteocalcin and, after correction for adiposity, thigh muscle volume. This may have implications for how BAT interacts with both bone and muscle tissue.

    In paper IV the glucose uptake of BAT during cooling of adult humans was measured using 18F-FDG PET. Additionally, their BAT FF was measured using MRI, and their skin temperature during cooling near a major BAT depot was measured using infrared thermography (IRT). It was found that both the BAT FF and the temperature measured using IRT correlated with the BAT glucose uptake, meaning these measurements could be potential alternatives to 18F-FDG PET in future studies of BAT.

  • Incidental Gallbladder Cancer : Incidence, predictors, management and outcome in a Swedish population Author: Linda Lundgren Link: Publication date: 2019-08-23 11:00

    Background: Cholecystectomy is a common surgical procedure and incidental gallbladder cancer is a rare and unexpected finding at a cholecystectomy performed upon benign indications. Whether to perform routine or selective histopathology of the gallbladder specimen is still a subject for discussion. The prognosis of gallbladder cancer is largely affected by tumour stage and treatment.

    Aims: The overall aim was to study whether routine histological examination of the gallbladder specimen is of clinical and health economic value; determine if there are any predictive factors of incidental gallbladder cancer at benign cholecystectomy and compare the management and outcome of incidental gallbladder cancer patients in Sweden.

    Methods: All studies were based on registry data from GallRiks (The Swedish Registry for Gallstone Surgery and Endoscopic Retrograde Cholangiopancreatography) between 2007 and 2016, with some modifications between studies. Complemental cross-linkage was made to national registries, and medical records were reviewed. Papers I, II and III were population-based observational studies with prospectively and retrospectively collected data. Paper IV was a health economic evaluation based on the results from papers I and III.

    Results and conclusions: Hospitals submitting >75 per cent of gallbladder specimens diagnosed a higher proportion of incidental gallbladder cancer than did hospitals submitting ≤25 per cent of samples (paper I). Incidental gallbladder cancer was more prevalent in older patients, women and patients with acute or previous cholecystitis, as well as ongoing jaundice. The risk model based on predictive preoperative factors was further improved by adding a macroscopic assessment of the gallbladder (paper II). Predictive factors for gallbladder cancer appeared to have an impact on which specimens were submitted in hospitals with a selective approach of histopathology (paper I). For pT2 and pT3 patients, re-resection improved diseasespecific survival, although these groups differed in terms of age and comorbidity (paper III). Residual disease was an independent factor for impaired survival. A change to routine histopathology of gallbladder specimens in Sweden would lead to increased costs with little improved health outcomes. Instead, a more standardized approach to selective histology would be needed (paper IV).