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- Henriksson, Malin, 1981-, et al.
(author)
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Framtidens gröna praktiker : förutsättningar för omställningsagenter i mat- och transportsektorn
- 2022
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Reports (other academic/artistic)abstract
- Rapporten tar sin utgångspunkt i att det akuta klimatläget kräver nya mer cirkulära sätt att producera och konsumera varor och tjänster på. I rapporten ger vi exempel på lovande gröna initiativ och pekar på vilka svårigheter omställningsagenterna bakom dem möter. Fem ideella och vinstdrivande initiativ från matsektorn och transportsektorn studeras. I matsektorn finns det stor miljöpotential i att minska svinnet. Proteinskifte, från animaliskt kött och mejeri, till vegetabiliska motsvarigheter leder till en mer effektiv resurshantering. Det gäller särskilt när produktionen är lokal och långväga transporter kan undvikas. Hur mycket vatten och landareal som produktionen kräver påverkar miljöpotentialen. Produktion av havre- och ärtprodukter, som studerats i rapporten, kan leva upp till sådana krav, med villkoret att de ingår i cirkulära flöden där det inte produceras överskott. När det gäller transportsektorn har initiativ som stärker cykling en stor miljöpotential. Att dela på eller återbruka cyklar leder till mer effektiv resurshantering. Potentialen villkoras dock om användarna av cykelpooler eller cykelkök parallellt köper egna cyklar och kör bil. Med hjälp av teorier från miljö- och omställningsforskning belyser vi att omställningsagenter verkar inom regimer som bygger på linjära praktiker och fossila beroenden. Motståndet som omställnings[1]agenter möter kan vara mycket konkret, som att det är svårt att hitta betalningsvilliga användare men även handla om subtila processer som att behöva tilltala målgrupper som konsumenter snarare än medborgare. Omställningsagenterna tvingas på olika sätt anpassa sig till regimens spelregler, oavsett om det strider mot egna värderingar och visioner. De studerade initiativen illustrerar möjliga sätt att organisera framtiden på. Det gäller särskilt de ideella verksamheterna. I likhet med tidigare studier visar rapporten att förutsättningen för att omställningsagenter ska kunna visa vägen mot en grönare framtid är begränsad om inte lagstiftning, subventioner, och nya normer om ett gott liv stöttar dem.
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| 2. |
- Hultman, Martin, 1992-, et al.
(author)
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Comprehensive imaging of microcirculatory changes in the foot during endovascular intervention - A technical feasibility study
- 2022
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In: Microvascular Research. - Maryland Heights, MO, United States : Academic Press. - 0026-2862 .- 1095-9319. ; 141
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Journal article (peer-reviewed)abstract
- Chronic limb-threatening ischemia (CLTI) has a major impact on patient's lives and is associated with a heavy health care burden with high morbidity and mortality. Treatment by endovascular intervention is mostly based on macrocirculatory information from angiography and does not consider the microcirculation. Despite successful endovascular intervention according to angiographic criteria, a proportion of patients fail to heal ischemic lesions. This might be due to impaired microvascular perfusion and variations in the supply to different angiosomes. Non-invasive optical techniques for microcirculatory perfusion and oxygen saturation imaging have the potential to provide the interventionist with additional information in real-time, supporting clinical decisions during the intervention. This study presents a novel multimodal imaging system, based on multi-exposure laser speckle contrast imaging and multi-spectral imaging, for continuous use during endovascular intervention. The results during intervention display spatiotemporal changes in the microcirculation compatible with expected physiological reactions during balloon dilation, with initially induced ischemia followed by a restored perfusion, and local administration of a vasodilator inducing hyperemia. We also present perioperative and postoperative follow-up measurements with a pulsatile microcirculation perfusion. Finally, cases of spatial heterogeneity in the observed oxygen saturation and perfusion are discussed. In conclusion, this technical feasibility study shows the potential of the methodology to characterize changes in microcirculation before, during, and after endovascular intervention.
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| 3. |
- Hultman, Martin, 1992-, et al.
(author)
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Evaluation of a high framerate multi-exposure laser speckle contrast imaging setup
- 2018
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In: High-Speed Biomedical Imaging and Spectroscopy III. - : SPIE - International Society for Optical Engineering. - 9781510614963
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Conference paper (peer-reviewed)abstract
- We present a first evaluation of a new multi-exposure laser speckle contrast imaging (MELSCI) system for assessing spatial variations in the microcirculatory perfusion. The MELSCI system is based on a 1000 frames per second 1-megapixel camera connected to a field programmable gate arrays (FPGA) capable of producing MELSCI data in realtime. The imaging system is evaluated against a single point laser Doppler flowmetry (LDF) system during occlusionrelease provocations of the arm in five subjects. Perfusion is calculated from MELSCI data using current state-of-the-art inverse models. The analysis displayed a good agreement between measured and modeled data, with an average error below 6%. This strongly indicates that the applied model is capable of accurately describing the MELSCI data and that the acquired data is of high quality. Comparing readings from the occlusion-release provocation showed that the MELSCI perfusion was significantly correlated (R=0.83) to the single point LDF perfusion, clearly outperforming perfusion estimations based on a single exposure time. We conclude that the MELSCI system provides blood flow images of enhanced quality, taking us one step closer to a system that accurately can monitor dynamic changes in skin perfusion over a large area in real-time
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| 4. |
- Hultman, Martin, 1992-
(author)
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Real-time multi-exposure laser speckle contrast imaging of skin microcirculatory perfusion
- 2021
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Doctoral thesis (other academic/artistic)abstract
- The microcirculation, the blood flow in the smallest blood vessels in the body, has a vital function as this is where oxygen and nutrients diffuses from the blood to to the surrounding cells. An important quantity is the tissue perfusion, a measure of the microcirculation’s capacity to provide oxygen and nutrients to the cells. Laser speckle contrast imaging (LSCI) is a non-invasive optical technique that captures images of the microcirculatory perfusion by analysing the local contrast in the laser speckle pattern that forms when tissue is illuminated by a laser. LSCI has seen extensive use in clinical research due to the easy and cheap measurement setup, and high spatial and temporal resolution. Despite this, clinical acceptance and routine use remains low. Some of the drawbacks of the technique is a limitation to relative measurements in arbitrary units, as well as high susceptibility to measurement noise and confounding properties of the tissue. This makes comparisons difficult, especially between patients. An extension of LSCI called multi-exposure laser speckle contrast imaging (MELSCI) was proposed to deal with some of these issues, although the more complicated data acquisition and models prevented real-time use. MELSCI has in-stead been used exclusively as an offline technique where data is post-processed, and the clinical use has been non-existent. Furthermore, existing models for LSCI and MELSCI are designed for tissues where individual vessels are visible, such as the surface of the brain or on the retina. For measurements in the diffuse regime, such as on skin tissue, these models are no longer physiologically accurate, resulting in incorrect perfusion estimates.This thesis presents a MELSCI-based perfusion imaging instrument that is simultaneously fast and physiologically accurate for measurements of skin. There are three main parts to this work; development of a real-time MELSCI system, development of perfusion models for skin, and demonstration of the system in a clinical feasibility study.A real-time MELSCI instrument was developed based on a high-speed CMOS camera tightly integrated with algorithms in a field programmable gate array (FPGA). The algorithm was based on synthetic multi-exposure, where a set of 64 individual 1-ms images were digitally added to create multi-exposure images at 1, 2, 4, 8, 16, 32, and 64 ms. The resulting multi-exposure data was demonstrated to have high quality and less susceptibility to measurement noise than previous models. The instrument enabled continuous acquisition and analysis of MELSCI data in real-time at 15.6 frames per second, sufficiently fast to capture the temporal dynamics of the skin perfusion.To enable real-time estimation of accurate and physiologically relevant perfusion from the MELSCI data, two artificial neural networks were trained on synthetic data from a mathematical model of skin. The first estimated perfusion as computed by conventional laser Doppler flowmetry (LDF), demonstrating a high correlation between the two methods. The second estimated true perfusion in absolute units %RBC × mm/s separated into three distinct speed components, 0-1 mm/s, 1-10 mm/s and >10 mm/s. The ANNs removed the need for iterative optimization algorithms, resulting in more than 1000x speed-up over previous methods, and enabled real-time use in an imaging setting.The instrument was demonstrated in controlled experiments on healthy volunteers, using standardized occlusion-release provocations, and in a clinical feasibility study where the foot perfusion was monitored during endovascular interventions in patients with chronic limb-threatening ischemia. The instrument enabled continuous imaging of perfusion, with sufficiently high framerate to capture the pulsatile dynamics, or lack thereof, at each point in time. The necessity for both high spatial and temporal resolution to properly asses the microcirculation was demonstrated.The advancements to MELSCI proposed in this thesis has the potential to improve the clinical viability of the technique, increase interpretability of the results, and might lead to improved treatments based on a better understanding of the complex processes in the microcirculation.
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