| 1. |
- Eneman, K., et al.
(författare)
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Evaluation of signal enhancement algorithms for hearing instruments
- 2008
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Konferensbidrag (refereegranskat)abstract
- In the frame of the HearCom1 project five promising signal enhancement algorithms are validated for future use in hearing instrument devices. To assess the algorithm performance solely based on simulation experiments, a number of physical evaluation measures have been proposed that incorporate basic aspects of normal and impaired human hearing. Additionally, each of the algorithms has been implemented on a common real-time hardware/software platform, which facilitates a profound subjective validation of the algorithm performance. Recently, a multicenter study has been set up across five different test centers in Belgium, the Netherlands, Germany and Switzerland to perceptually evaluate the selected signal enhancement approaches with normally hearing and hearing impaired listeners.
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| 2. |
- van Beek, Sten M. M., et al.
(författare)
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Effect of β2-agonist treatment on insulin-stimulated peripheral glucose disposal in healthy men in a randomised placebo-controlled trial
- 2023
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- β2-agonist treatment improves skeletal muscle glucose uptake and whole-body glucose homeostasis in rodents, likely via mTORC2-mediated signalling. However, human data on this topic is virtually absent. We here investigate the effects of two-weeks treatment with the β2-agonist clenbuterol (40 µg/day) on glucose control as well as energy- and substrate metabolism in healthy young men (age: 18-30 years, BMI: 20-25 kg/m2) in a randomised, placebo-controlled, double-blinded, cross-over study (ClinicalTrials.gov-identifier: NCT03800290). Randomisation occurred by controlled randomisation and the final allocation sequence was seven (period 1: clenbuterol, period 2: placebo) to four (period 1: placebo, period 2: clenbuterol). The primary and secondary outcome were peripheral insulin-stimulated glucose disposal and skeletal muscle GLUT4 translocation, respectively. Primary analyses were performed on eleven participants. No serious adverse events were reported. The study was performed at Maastricht University, Maastricht, The Netherlands, between August 2019 and April 2021. Clenbuterol treatment improved peripheral insulin-stimulated glucose disposal by 13% (46.6 ± 3.5 versus 41.2 ± 2.7 µmol/kg/min, p = 0.032), whereas skeletal muscle GLUT4 translocation assessed in overnight fasted muscle biopsies remained unaffected. These results highlight the potential of β2-agonist treatment in improving skeletal muscle glucose uptake and underscore the therapeutic value of this pathway for the treatment of type 2 diabetes. However, given the well-known (cardiovascular) side-effects of systemic β2-agonist treatment, further exploration on the underlying mechanisms is needed to identify viable therapeutic targets.
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| 5. |
- Gustafsson, Agnetha, et al.
(författare)
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Evaluation of attenuation corrections using Monte Carlo simulated lung SPECT
- 1998
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 43:8, s. 2325-2336
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Tidskriftsartikel (refereegranskat)abstract
- SPECT (single photon emission computed tomography) images are distorted by photon attenuation. The effect is complex in the thoracic region due to different tissue densities. This study compares the effect on the image homogeneity of two different methods of attenuation correction in lung SPECT; one pre-processing and one post-processing method. This study also investigates the impact of attenuation correction parameters such as lung contour, body contour, density of the lung tissue and effective attenuation coefficient. The Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing a homogeneous activity distribution in the lung. Homogeneity in reconstructed images was calculated as the coefficient of variation (CV). The isolated effect of the attenuation correction was assessed by normalizing pixel values from the attenuation corrected lung by pixel values from the lung with no attenuation effects. Results show that the CV decreased from 12.8% with no attenuation correction to 4.4% using the post-processing method and true densities in the thoracic region. The impact of variations in the definition of the body contour was found to be marginal while the corresponding effect of variations in the lung contour was substantial
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| 6. |
- Johansson, Åke, 1955, et al.
(författare)
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Detection of chronic rejection by quantitative ventilation scintigrams in lung-transplanted patients: a pilot study
- 2005
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Ingår i: Clin Physiol Funct Imaging. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- Summary The suspicion of chronic rejection [bronchiolithis obliterans syndrome (BOS)] is usually based on deteriorating forced expired volume in 1 s. It is however, desirable to develop more sensitive methods as increased anti-inflammatory therapy is thought to stop progression of the rejection. The aim of the present study was to develop quantitative tools based on ventilation scintigrams, to diagnose BOS. Sixteen double-lung-transplanted patients participated, six developing BOS and 10 who did not develop BOS. They were investigated with planar posterior-anterior (99m)Tc-Technegas (Tetley Manufacturing Ltd, Sydney, Australia) ventilation scintigraphy at baseline, 6 months to 1 year post-transplantation, and at a follow-up examination 3-4-year post-transplant or in the BOS patients close to the time of the diagnosis. An automatic region of interest (ROI) was drawn on each lung in the scintigraphic image at baseline and also applied to the follow-up investigation. The area inside the ROI was subdivided into stripes 10.8 mm high and squares 10.8 x 10.8 mm wide. Corresponding stripes and squares in baseline and follow-up were analysed regarding differences in relative retention. The results show that the square analysis is superior. Applying chosen cut-off values for square element differences, 6/6 right and 5/6 left BOS lungs were identified and one left and one right lung of patients not developing BOS were misclassified. We conclude that the square element difference appears to be a promising method to diagnose BOS.
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| 7. |
- Moonen, M., et al.
(författare)
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Effects of lung volume reduction surgery on distribution of ventilation and perfusion
- 2005
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Ingår i: Clin Physiol Funct Imaging. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- Summary Lung volume reduction surgery (LVRS) results in functional improvements in most patients. The mechanisms behind the improvements are not clear. We hypothesized that reduced inequalities in ventilation to perfusion ratio (V/Q) may be a contributing explanation. Nine patients who underwent LVRS were investigated by ventilation and perfusion scintigrams before and after surgery. In addition, 8 healthy subjects were investigated once. The relative ventilation, perfusion and V/Q were calculated in 1 x 1 cm lung elements. Normal range of the element count-rate was determined by the corresponding results in the normal subjects. Results of this small study show a significant effect of LVRS on V/Q, with reduction of shunt-like elements. We conclude that the functional improvement after LVRS to some extent may be explained by decreased V/Q inequality.
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