| 11. |
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| 12. |
- Romu, Thobias, et al.
(författare)
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MANA - Multi scale adaptive normalized averaging
- 2011
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Ingår i: 2011 IEEE International Symposium on Biomedical Imaging: From Nano to Macro. - : IEEE conference proceedings. - 9781424441280 ; , s. 361-364
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Konferensbidrag (refereegranskat)abstract
- It is possible to correct intensity inhomogeneity in fat–water Magnetic Resonance Imaging (MRI) by estimating a bias field based on the observed intensities of voxels classified as the pure adipose tissue. The same procedure can also be used to quantify fat volume and its distribution which opens up for new medical applications. The bias field estimation method has to be robust since pure fat voxels are irregularly located and the density varies greatly within and between image volumes. This paper introduces Multi scale Adaptive Normalized Average (MANA) that solves this problem bybasing the estimate on a scale space of weighted averages. By usingthe local certainty of the data MANA preserves details where the local data certainty is high and provides realistic values in sparse areas.
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| 13. |
- Grubb, Anders, et al.
(författare)
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Cystatin C, a marker for successful aging and glomerular filtration rate, is not influenced by inflammation.
- 2011
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 71, s. 145-149
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Background. The plasma level of cystatin C is a better marker than plasma creatinine for successful aging. It has been assumed that the advantage of cystatin C is not only due to it being a better marker for glomerular filtration rate (GFR) than creatinine, but also because an inflammatory state of a patient induces a raised cystatin C level. However, the observations of an association between cystatin C level and inflammation stem from large cohort studies. The present work concerns the cystatin C levels and degree of inflammation in longitudinal studies of individual subjects without inflammation, who undergo elective surgery. Methods. Cystatin C, creatinine, and the inflammatory markers CRP, serum amyloid A (SAA), haptoglobin and orosomucoid were measured in plasma samples from 35 patients the day before elective surgery and subsequently during seven consecutive days. Results. Twenty patients had CRP-levels below 1 mg/L before surgery and low levels of the additional inflammatory markers. Surgery caused marked inflammation with high peak values of CRP and SAA on the second day after the operation. The cystatin C level did not change significantly during the observation period and did not correlate significantly with the level of any of the four inflammatory markers. The creatinine level was significantly reduced on the first postoperative day but reached the preoperative level towards the end of the observation period. Conclusion. The inflammatory status of a patient does not influence the role of cystatin C as a marker of successful aging, nor of GFR.
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| 14. |
- Fredenberg, Erik, PhD, 1979-, et al.
(författare)
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Contrast-enhanced spectral mammography with a photon-counting detector
- 2010
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405. ; 37:5, s. 2017-2029
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Spectral imaging is a method in medical x-ray imaging to extract information about the object constituents by the material-specific energy dependence of x-ray attenuation. In particular, the detectability of a contrast agent can be improved over a lumpy background. We have investigated a photon-counting spectral imaging system with two energy bins for contrast-enhanced mammography. System optimization and the potential benefit compared to conventional non-energy-resolved imaging was studied.Methods: A framework for system characterization was set up that included quantum and anatomical noise, and a theoretical model of the system was benchmarked to phantom measurements.Results: It was found that optimal combination of the energy-resolved images corresponded approximately to minimization of the anatomical noise, and an ideal-observer detectability index could be improved more than a factor of two compared to absorption imaging in the phantom study. In the clinical case, an improvement close to 80% was predicted for an average glandularity breast, and a factor of eight for dense breast tissue. Another 70% was found to be within reach for an optimized system.Conclusions: Contrast-enhanced spectral mammography is feasible and beneficial with the current system, and there is room for additional improvements.
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| 15. |
- Nyberg, Lars, et al.
(författare)
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Memory aging and brain maintenance
- 2012
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Ingår i: Trends in cognitive sciences. - : Elsevier BV. - 1364-6613 .- 1879-307X. ; 16:5, s. 292-305
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Tidskriftsartikel (refereegranskat)abstract
- Episodic memory and working memory decline with advancing age. Nevertheless, large-scale population-based studies document well-preserved memory functioning in some older individuals. The influential 'reserve' notion holds that individual differences in brain characteristics or in the manner people process tasks allow some individuals to cope better than others with brain pathology and hence show preserved memory performance. Here, we discuss a complementary concept, that of brain maintenance (or relative lack of brain pathology), and argue that it constitutes the primary determinant of successful memory aging. We discuss evidence for brain maintenance at different levels: cellular, neurochemical, gray- and white-matter integrity, and systems-level activation patterns. Various genetic and lifestyle factors support brain maintenance in aging and interventions may be designed to promote maintenance of brain structure and function in late life.
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| 16. |
- Nyberg, Jan, 1960-, et al.
(författare)
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Osseointegration of implants in irradiated bone with and without hyperbaric oxygen treatment : an experimental study in rat tibiae
- 2013
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Ingår i: International Journal of Oral & Maxillofacial Implants. - : Quintessence Publishing Co., Inc.. - 0882-2786 .- 1942-4434. ; 28:3, s. 739-746
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Hyperbaric oxygen (HBO) has been recommended to enhance implant osseointegration in irradiated bone. The aim of this study was to further investigate the effects of HBO on implant integration in irradiated bone tissue.Materials and Methods: The present study was an experimental intraindividual study in 16 rats. A single fraction of 20 Gy external irradiation was applied to one rat hind leg, while the other served as a nonirradiated control. Three days after radiation, two implants were inserted in each tibial tuberosity. The rats were divided into two groups: non-HBO treated (group 1) and HBO treated (group 2). Five weeks after radiation, removal torque tests were performed. Implants with surrounding tissue were processed to undecalcified cut and ground sections for histomorphometric evaluations of bone-to-implant contact and bone area. Retrieved bones were also investigated with dual-energy x-ray absorptiometry.Results: The non-HBO treated rats (group 1) demonstrated higher, but not statistically significantly higher, values in the nonirradiated leg for all investigated parameters compared to the HBO-treated rats (group 2). However, the mean value for bone area was significantly higher in the irradiated sides compared to the nonirradiated control sides.Conclusions: In the present study, HBO treatment did not have a significant impact on osseointegration of implants in irradiated bone.
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| 17. |
- Sandström, Agneta, 1959-
(författare)
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Neurocognitive and endocrine dysfunction in women with exhaustion syndrome
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stress has emerged as one of the most important factors to consider in psychiatric diagnoses and has become a common reason for long-term sick leave (LTSL). Roughly 50% of LTSL due to psychiatric diseases are thought to be associated with work-related stress. The demarcation towards major depression is disputed, and no international consensus exists for how to diagnose and rehabilitate these individuals. The Swedish National Board of Health has suggested the term “exhaustion syndrome” to integrate these individuals into stress-related disorders. Prominent features of this syndrome are fatigue, sleeping disorders, and cognitive dysfunction. The cognitive dysfunction may be due to an interaction between personality features, environmental factors, the biological effects of stress hormones, and dysfunction in key brain areas, notably the hippocampus and prefrontal cortex. A consistent feature of chronic stress is activation of the cortisol, or hypothalamic-pituitary-adrenal, axis, which may be linked to cognitive dysfunction. Increased glucocorticoid levels, mainly cortisol in humans, are known to impair memory performance. The aim of this thesis was to investigate whether patients with exhaustion syndrome exhibit specific alterations in an extensive set of biological, psychological and immunological variables. Patients in Study 1 had significant cognitive impairment for specific tasks assumed to tap frontal lobe functioning. In Study 2 anxiety prone, worrying, pessimistic individuals with low executive drive and a persistent personality type were more likely to develop exhaustion syndrome. Decreased reactivity was found on the pituitary level after corticotropin releasing hormone (CRH) in exhaustion syndrome patients. The cortisol/adrenocorticotropic hormone response to CRH was slightly higher in patients compared to controls, indicating increased sensitivity at the adrenal cortex level. No differences were found in hippocampal volume. In Study 3, functional imaging revealed a different pattern of brain activation in working memory tests in patients with exhaustion syndrome compared to healthy individuals and patients with depression. In summary, our data suggests an intimate link between personality and wellbeing, cognitive performance and neuroendocrine dysfunction, in exhaustion syndrome. We thus find similarities with major depression but also distinct differences between the exhaustion syndrome and major depression.
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| 18. |
- Johansson, Björn
(författare)
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Opacification of anterior part of hydrophilic acrylic IOL or a prelenticular inflammatory membrane?
- 2012
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Ingår i: Journal of cataract and refractive surgery. - Philadelphia : Elsevier. - 0886-3350 .- 1873-4502. ; 38:6, s. 1115-1116
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Tidskriftsartikel (refereegranskat)abstract
- In their recent case report, Park and Chuck1 describe the bilateral appearance of an opacification at the plane of the anterior surface of the hydrophilic acrylic Akreos MI60 intraocular lens (IOL) (Bausch & Lomb). The patient's general history of diabetes mellitus, proliferative retinopathy, and iris rubeosis explains the limited pupil dilation preventing visualization of the capsulorhexis opening in their slitlamp images.
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| 19. |
- Gingnell, Malin, 1982-
(författare)
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Ovarian Steroid Hormones, Emotion Processing and Mood
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is known that some psychiatric disorders may deteriorate in relation to the menstrual cycle. However, in some conditions, such as premenstrual dysphoric disorder (PMDD), symptomatology is triggered mainly by the variations in ovarian steroid hormones. Although symptoms induced by fluctuations in ovarian steroids often are affective, little is known about how emotion processing in women is influenced by variations, or actual levels, of ovarian steroid hormones.The general aim of this thesis was to evaluate menstrual cycle effects on reactivity in emotion generating and controlling areas in the corticolimbic system to emotional stimulation and anticipation, in healthy controls and women with PMDD. A second aim was to evaluate corticolimbic reactivity during long-term administration of exogenous ovarian steroids.In study I, III and IV effects of the menstrual cycle on emotional reactivity in women with PMDD was studied. In study I, women with PMDD in displayed higher amygdala reactivity than healthy controls to emotional faces, not in the luteal phase as was hypothesised, but in the follicular phase. No difference between menstrual cycle phases was obtained in women with PMDD, while healthy controls had an increased reactivity in the luteal phase. The results of study I was further elaborated in study III, where women with PMDD were observed to have an increased anticipatory reactivity to negative emotional stimuli. However, no differences in amygdala reactivity to emotional stimuli were obtained across the menstrual cycle. Finally, in study IV the hypothesis that amygdala reactivity increase in the luteal phase in women with PMDD is linked to social stimuli rather than generally arousing stimuli was suggested, tested and supported.In study II, re-exposure to COC induced mood symptoms de novo in women with a previous history of COC-induced adverse mood. Women treated with COC reported increased levels of mood symptoms both as compared to before treatment, and as compared to the placebo group. There was a relatively strong correlation between depressive scores before and during treatment. The effects of repeated COC administration on subjective measures and brain function were however dissociated with increased aversive experiences accompanied by reduced reactivity in the insular cortex.
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| 20. |
- Fredenberg, Erik, PhD, 1979-, et al.
(författare)
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Energy filtering with x-ray lenses: Optimization for photon-counting mammography
- 2010
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 139, s. 339-342
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Tidskriftsartikel (refereegranskat)abstract
- Chromatic properties of the multi-prism and prism-array x-ray lenses (MPL and PAL) can potentially be utilized for efficient energy filtering and dose reduction in mammography. The line-shaped foci of the lenses are optimal for coupling to photon-counting silicon strip detectors in a scanning system. A theoretical model was developed and used to investigate the benefit of two lenses compared to an absorption-filtered reference system. The dose reduction of the MPL filter was 15% compared to the reference system at matching scan time, and the spatial resolution was higher. The dose of the PAL-filtered system was found to be 20% lower than for the reference system at equal scan time and resolution, and only 20% higher than for a monochromatic beam. An investigation of some practical issues remains, including the feasibility of brilliant-enough x-ray sources and manufacturing of a polymer PAL.
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