| 1. |
- Anesäter, Erik, et al.
(författare)
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The influence of different sizes and types of wound fillers on wound contraction and tissue pressure during negative pressure wound therapy.
- 2011
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Ingår i: International Wound Journal. - 1742-481X. ; 8, s. 336-342
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Tidskriftsartikel (refereegranskat)abstract
- Negative pressure wound therapy (NPWT) contracts the wound and alters the pressure in the tissue of the wound edge, which accelerates wound healing. The aim of this study was to examine the effect of the type (foam or gauze) and size (small or large) of wound filler for NPWT on wound contraction and tissue pressure. Negative pressures between -20 and -160 mmHg were applied to a peripheral porcine wound (n = 8). The pressure in the wound edge tissue was measured at distances of 0·1, 0·5, 1·0 and 2·0 cm from the wound edge and the wound diameter was determined. At 0·1 cm from the wound edge, the tissue pressure decreased when NPWT was applied, whereas at 0·5 cm it increased. Tissue pressure was not affected at 1·0 or 2·0 cm from the wound edge. The tissue pressure, at 0·5 cm from the wound edge, was greater when using a small foam than when using than a large foam. Wound contraction was greater when using a small foam than when using a large foam during NPWT. Gauze resulted in an intermediate wound contraction that was not affected by the size of the gauze filler. The use of a small foam to fill the wound causes considerable wound contraction and may thus be used when maximal mechanical stress and granulation tissue formation are desirable. Gauze or large amounts of foam result in less wound contraction which may be beneficial, for example when NPWT causes pain to the patient.
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| 2. |
- Anna Karin, Hedström, et al.
(författare)
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The impact of bariatric surgery on disease activity and progression of multiple sclerosis : A nationwide matched cohort study
- 2022
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Ingår i: Multiple Sclerosis Journal. - : Sage Publications. - 1352-4585 .- 1477-0970. ; 28:13, s. 2099-2105
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Surgical outcomes in patients with multiple sclerosis (MS) following metabolic surgery appear to be similar compared to those of the general bariatric population.OBJECTIVE: To study the impact of metabolic surgery on the clinical course of MS.METHODS: Using data from the Scandinavian Obesity Surgery Registry and the Swedish Multiple Sclerosis register, we compared disease outcomes in 122 cases of MS who had undergone metabolic surgery with those of 122 cases of MS without surgery, matched by a two-staged Propensity score match, including age at disease onset, sex, MS phenotype, body mass index, and preoperative severity of MS as measured by the Expanded Disability Status Scale.RESULTS: The time to 6-month confirmed disability progression during the first five years postbaseline was shorter among the surgical patients (hazard ratio (HR) = 2.31, 95% confidence interval (CI) = 1.09-4.90; p = 0.03). No differences were observed regarding postoperative annual relapse rate (p = 0.24) or time to first postoperative relapse (p = 0.52).CONCLUSION: Although metabolic surgery appears to be a safe and efficient treatment of obesity in patients with MS, the clinical course of the disease might be negatively affected. Long-term nutritional follow-up after surgery and supplementation maintenance are crucial, particularly among those with preoperative deficits.
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| 3. |
- Bergvall, Erik, et al.
(författare)
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Spline-based cardiac motion tracking using velocity-encoded magnetic resonance imaging.
- 2008
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Ingår i: IEEE Transactions on Medical Imaging. - 1558-254X. ; 27:8, s. 1045-1053
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the problem of tracking cardiac motion and deformation using velocity-encoded magnetic resonance imaging. We expand upon an earlier described method and fit a spatiotemporal motion model to measured velocity data. We investigate several different spatial elements both qualitatively and quantitatively using phantom measurements and data from human subjects. In addition, we also use optical flow estimation by the Horn-Schunk method as complementary data in regions where the velocity measurements are noisy. Our results show that it is possible to obtain good motion tracking accuracy in phantoms with relatively few spatial elements, if the type of element is properly chosen. The use of optical flow can correct some measurement artifacts but may give an underestimation of the magnitude of the deformation. In human subjects the different spatial elements perform quantitatively in a similar way but qualitative differences exists, as shown by a semiquantitative visual scoring of the different methods.
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| 4. |
- Borgquist, Ola, et al.
(författare)
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Measurements of wound edge microvascular blood flow during negative pressure wound therapy using thermodiffusion and transcutaneous and invasive laser Doppler velocimetry
- 2011
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Ingår i: Wound Repair and Regeneration. - 1524-475X. ; 19:6, s. 727-733
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Tidskriftsartikel (refereegranskat)abstract
- The effects of negative pressure wound therapy (NPWT) on wound edge microvascular blood flow are not clear. The aim of the present study was therefore to further elucidate the effects of NPWT on periwound blood flow in a porcine peripheral wound model using different blood flow measurement techniques. NPWT at -20, -40, -80, and -125 mmHg was applied to a peripheral porcine wound (n = 8). Thermodiffusion, transcutaneous, and invasive laser Doppler velocimetry were used to measure the blood perfusion 0.5, 1.0, and 2.5 cm from the wound edge. Thermodiffusion (an invasive measurement technique) generally showed a decrease in perfusion close to the wound edge (0.5 cm), and an increase further from the edge (2.5 cm). Invasive laser Doppler velocimetry showed a similar response pattern, with a decrease in blood flow 0.5 cm from the wound edge and an increase further away. However, 1.0 cm from the wound edge blood flow decreased with high pressure levels and increased with low pressure levels. A different response pattern was seen with transcutaneous laser Doppler velocimetry, showing an increase in blood flow regardless of the distance from the wound edge (0.5, 1.0, and 2.5 cm). During NPWT, both increases and decreases in blood flow can be seen in the periwound tissue depending on the distance from the wound edge and the pressure level. The pattern of response depends partly on the measurement technique used. The combination of hypoperfusion and hyperperfusion caused by NPWT may accelerate wound healing.
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| 5. |
- Claesson, Erik, 1988-
(författare)
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Carbides in martensitic medium carbon low alloyed tool steels studied with small angle scattering techniques, electron microscopy and atom probe tomography
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Medium carbon low alloyed tool steels are used today in various areas to shape plastics, nonferrous metals, and steels, and they are crucial in the manufacturing industry. To be effective, tool steels must be strong and tough, and have high wear resistance and temperature stability. To achievethe desired properties, materials are alloyed so that secondary phaseparticles precipitate during processing, especially during the tempering of martensitic steels. However, the hardening contribution relates to the size,volume fraction and number density of precipitates, controlled by alloy composition and heat-treating parameters. It is therefore essential to understand how, where, and when the particles nucleate and how the precipitation sequence and kinetics are affected by alloying additions,tempering temperature, and time.This work is aimed to study carbide precipitation in two commercial low-alloy tool steel using small-angle neutron and X-ray scattering. To support these methods, samples were characterized with transmission electronmicroscopy (TEM) and atom probe tomography (APT). With a combination of high-resolution techniques, it was possible to establish the precipitation sequence in these steels. It was also possible with various small angle scattering techniques to determine the evolution of volume fraction and number density of precipitates as a function of tempering parameters.First, small angle neutron scattering (SANS) was used, which is an excellent method for bulk quantification of small precipitates in steel. It was possible with SANS to broadly study the precipitation process depending on annealing temperature and time. However, it is difficult with regular small angle scattering (SAS) to distinguish particle types with overlapping size distributions. To possibly separate the scattering signal from different carbide types, measurements were carried out with polarized small angle neutron scattering (SANSPOL) and anomalous small-angle X-ray scattering(ASAXS). With ASAXS it was possible to isolate the signal from molybdenum-rich carbides from other types of carbides.With SANSPOL, it was possible to follow the enrichment of alloy elements in cementite. The appearance of cementite can be described as an iron-richcore with a chromium-enriched shell. The partitioning of substitutional elements affects the stability of cementite and the alloy carbides. It was also possible with SANSPOL, during heating, to follow the initial precipitation of particles.Results from different experimental methods have been compared with precipitation simulations using thermodynamics-based precipitationmodeling. Equilibrium calculations indicates the possible stability ofdifferent precipitates, and the kinetics are captured with tools such as TCPRISMA to simulate structure evolution during tempering. Hardness measurements were made to correlate structure evolution to mechanical properties.
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| 6. |
- Hedström, Erik, et al.
(författare)
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Effects of gadolinium contrast agent on aortic blood flow and myocardial strain measurements by phase-contrast cardiovascular magnetic resonance
- 2010
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Ingår i: Journal of Cardiovascular Magnetic Resonance. - 1097-6647. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Quantitative blood flow and aspects of regional myocardial function such as myocardial displacement and strain can be measured using phase-contrast cardiovascular magnetic resonance (PC-CMR). Since a gadolinium-based contrast agent is often used to measure myocardial infarct size, we sought to determine whether the contrast agent affects measurements of aortic flow and myocardial displacement and strain. Phase-contrast data pre and post contrast agent was acquired during free breathing using 1.5T PC-CMR. Results: For aortic flow and regional myocardial function 12 and 17 patients were analysed, respectively. The difference pre and post contrast agent was 0.03 +/- 0.16 l/min for cardiac output, and 0.1 +/- 0.5 mm for myocardial displacement. Linear regression for myocardial displacement (MD) after and before contrast agent (CA) showed MDpostCA = 0.95MD(preCA)+0.05 (r = 0.95, p < 0.001). For regional myocardial function, the contrast-to-noise ratios for left ventricular myocardial wall versus left ventricular lumen were pre and post contrast agent administration 7.4 +/- 3.3 and 4.4 +/- 8.9, respectively (p < 0.001). The contrast-to-noise ratios for left ventricular myocardial wall versus surrounding tissue were pre and post contrast agent administration -16.9 +/- 22 and -0.2 +/- 6.3, respectively (p < 0.0001). Conclusions: Quantitative measurements of aortic flow yield equal results both in the absence and presence of gadolinium contrast agent. The total examination time may thereby be reduced when assessing both viability and quantitative flow using PC-CMR, by assessing aortic flow post contrast agent administration. Phase-contrast information for myocardial displacement is also assessable both in the absence and presence of contrast agent. However, delineation of the myocardium may be difficult or impossible post contrast agent due to the lower image contrast. Acquisition of myocardial displacement should therefore be performed pre contrast agent using current PC-CMR sequences.
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| 7. |
- Hedström, Erik, et al.
(författare)
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Model based cardiac motion tracking using velocity encoded magnetic resonance imaging
- 2007
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Ingår i: Image Analysis (Lecture Notes in Computer Science). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. - 9783540730392 ; 4522, s. 82-91
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Konferensbidrag (refereegranskat)abstract
- This paper deals with model based regularization of velocity encoded cardiac magnetic resonance images (MRI). We extend upon an existing spatiotemporal model of cardiac kinematics by considering data certainty and regularity of the model in order to improve its performance. The method was evaluated using a computer simulated phantom and using in vivo gridtag MRI as gold standard. We show, both quantitatively and qualitatively, that our modified model performs better than the original one.
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| 8. |
- Stenberg, Erik, 1979-, et al.
(författare)
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Bariatric and metabolic surgery in patients with morbid obesity and multiple sclerosis : a nationwide, matched cohort study
- 2021
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Ingår i: Surgery for Obesity and Related Diseases. - : Elsevier. - 1550-7289 .- 1878-7533. ; 17:6, s. 1108-1114
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Despite an association between obesity and multiple sclerosis (MS), very little is known regarding the safety and efficacy outcomes for patients with MS and severe obesity undergoing metabolic surgery.OBJECTIVES: The aim of the present study was to evaluate early complications and efficacy outcomes of metabolic surgery in patients with severe obesity and MS.SETTING: Nationwide, Sweden.METHODS: In this, matched cohort study, 196 patients with an MS diagnosis in the Swedish MS register who were undergoing metabolic surgery (gastric bypass or sleeve gastrectomy) with a registration in the Scandinavian Obesity Surgery Registry (SOReg) were matched 1:10 with a control group without MS diagnosis from the SOReg. A 2-stage matching procedure was used (exact match by surgical method, followed by propensity Score matching, including age, sex, preoperative BMI, surgical center, surgical access, year of surgery, hypertension, diabetes, sleep apnea, and dyslipidemia).RESULTS: Weight loss at 2 years after surgery was similar for patients with MS and controls (total weight loss 31.6 ± 9.1 versus 31.8 ± 9.2, P = .735). No significant differences were seen in either the overall postoperative complication rate (7.9% versus 7.2%, P = .778), or serious postoperative complications (3.7% versus 2.8%, P = .430). All aspects of health-related quality of life (HRQoL) improved in both groups but less so for the physical aspects of HRQoL in patients with MS.CONCLUSION: Metabolic surgery is a safe and efficient treatment for severe obesity in patients with MS, and it leads to subsequent improvements in HRQoL. Further studies addressing the effects of metabolic surgery on MS-related symptoms are needed.
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