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  • 1.
    Jonsson, Ove
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
    Morell, Arvid
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Zemgulis, Vitas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Thoracic Surgery.
    Lundström, Elin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Tovedal, Thomas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
    Myrdal Einarsson, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Thoracic Surgery.
    Thelin, Stefan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Thoracic Surgery.
    Ahlström, Håkan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Björnerud, Atle
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Lennmyr, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
    Minimal Safe Arterial Blood Flow During Selective Antegrade Cerebral Perfusion at 20° Centigrade2011In: Annals of Thoracic Surgery, ISSN 0003-4975, E-ISSN 1552-6259, Vol. 91, no 4, p. 1198-1205Article in journal (Refereed)
    Abstract [en]

    Background

    Selective antegrade cerebral perfusion (SACP) enables surgery on the aortic arch, where cerebral ischemia may cause neurologic sequels. This study aims to identify the minimum arterial flow level to maintain adequate cerebral perfusion during SACP in deep hypothermia in the pig.

    Methods

    Two groups of pigs were subjected to SACP at 20°C α-stat. In group 1 (n = 6), flow was stepwise adjusted from 8-6-4-2-8 mL · kg−1 · min−1 and in group 2 (n = 5), flow was kept constant at 6 mL · kg−1 · min−1. Magnetic resonance imaging and spectroscopy were performed at each flow level together with hemodynamic monitoring and blood gas analysis. The biochemical marker of cerebral damage protein S100β was measured in peripheral blood.

    Results

    Decreased mixed venous oxygen saturation and increased lactate in magnetic resonance spectroscopy was seen as a sign of anaerobic metabolism below 6 mL · kg−1 · min−1. No ischemic damage was seen on diffusion-weighted imaging, but the concentrations of S100β were significantly elevated in group 1 compared with group 2 at the end of the experiment (p < 0.05). Perfusion-weighted imaging showed coherence between flow setting and cerebral perfusion, increase of blood volume across time, and regional differences in perfusion during SACP.

    Conclusions

    The findings suggest an ischemic threshold close to 6 mL · kg−1 · min−1 in the present model. Regional differences in perfusion during SACP may be of pathogenic importance to focal cerebral ischemia.

  • 2.
    Lundström, Elin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Magnetic Resonance Imaging of Human Brown Adipose Tissue: Methodological Development and Application2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Brown adipose tissue (BAT) is a thermogenic organ with the main human depot located in the cervical-supraclavicular (sBAT) region. BAT is proposed as a potential therapeutic target for obesity and diabetes. This thesis aims to contribute to the development of magnetic resonance imaging (MRI)-based methods and to the application of these in studies of human BAT. Water-fat MRI enables separation of water and fat, the dominant contributors to the MR signal, and the quantification of fat fraction (FF) and effective transverse relaxation rate (R2*). FF and R2* are often used in studies of human BAT, e.g. for characterizing the tissue and distinguishing it from white adipose tissue. A Cooling-reheating protocol was introduced for studying changes in sBAT, related to lipid content and perfusion. sBAT FF decreased after cold exposure. The sustained low FF after reheating suggested lipid consumption as the primary cause. This conclusion was based on the assumption of a normalized perfusion after reheating. An automated method for segmentation of sBAT was developed. The method compared well with a semi-automated reference method with respect to segmentation overlap and estimated mean sBAT FF and R2*. A modified version of the automated method was applied to a large-scale study where an association between sBAT FF and glucose tolerance indicated a role for BAT in glucose metabolism, potentially linked to the risk of developing diabetes.  A Cooling-reheating protocol was evaluated with positron emission tomography measurements of perfusion and cold-stimulated BAT activity. Inverse correlations between sBAT FF and BAT activity suggested sBAT FF to predict cold-induced BAT activity. After reheating, the cold-induced increase in perfusion normalized and the cold-induced decrease in FF partially normalized. This suggested potential decreases in FF after reheating to mainly be due to lipid consumption and decreases in FF after cold exposure to possibly be influenced by perfusion.

    List of papers
    1. Magnetic resonance imaging cooling–reheating protocol indicates decreased fat fraction via lipid consumption in suspected brown adipose tissue
    Open this publication in new window or tab >>Magnetic resonance imaging cooling–reheating protocol indicates decreased fat fraction via lipid consumption in suspected brown adipose tissue
    Show others...
    2015 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 4, article id e0126705Article in journal (Refereed) Published
    Abstract [en]

    OBJECTIVES: To evaluate whether a water-fat magnetic resonance imaging (MRI) cooling-reheating protocol could be used to detect changes in lipid content and perfusion in the main human brown adipose tissue (BAT) depot after a three-hour long mild cold exposure.

    MATERIALS AND METHODS: Nine volunteers were investigated with chemical-shift-encoded water-fat MRI at baseline, after a three-hour long cold exposure and after subsequent short reheating. Changes in fat fraction (FF) and R2*, related to ambient temperature, were quantified within cervical-supraclavicular adipose tissue (considered as suspected BAT, denoted sBAT) after semi-automatic segmentation. In addition, FF and R2* were quantified fully automatically in subcutaneous adipose tissue (not considered as suspected BAT, denoted SAT) for comparison. By assuming different time scales for the regulation of lipid turnover and perfusion in BAT, the changes were determined as resulting from either altered absolute fat content (lipid-related) or altered absolute water content (perfusion-related).

    RESULTS: sBAT-FF decreased after cold exposure (mean change in percentage points = -1.94 pp, P = 0.021) whereas no change was observed in SAT-FF (mean = 0.23 pp, P = 0.314). sBAT-R2* tended to increase (mean = 0.65 s-1, P = 0.051) and SAT-R2* increased (mean = 0.40 s-1, P = 0.038) after cold exposure. sBAT-FF remained decreased after reheating (mean = -1.92 pp, P = 0.008, compared to baseline) whereas SAT-FF decreased (mean = -0.79 pp, P = 0.008, compared to after cold exposure).

    CONCLUSIONS: The sustained low sBAT-FF after reheating suggests lipid consumption, rather than altered perfusion, as the main cause to the decreased sBAT-FF. The results obtained demonstrate the use of the cooling-reheating protocol for detecting changes in the cervical-supraclavicular fat depot, being the main human brown adipose tissue depot, in terms of lipid content and perfusion.

    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Computerized Image Processing
    Identifiers
    urn:nbn:se:uu:diva-254074 (URN)10.1371/journal.pone.0126705 (DOI)000353713100132 ()25928226 (PubMedID)
    Available from: 2015-04-30 Created: 2015-06-04 Last updated: 2019-04-15Bibliographically approved
    2. Automated segmentation of human cervical-supraclavicular adipose tissue in magnetic resonance images
    Open this publication in new window or tab >>Automated segmentation of human cervical-supraclavicular adipose tissue in magnetic resonance images
    Show others...
    2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 3064Article in journal (Refereed) Published
    Abstract [en]

    Human brown adipose tissue (BAT), with a major site in the cervical-supraclavicular depot, is a promising anti-obesity target. This work presents an automated method for segmenting cervical-supraclavicular adipose tissue for enabling time-efficient and objective measurements in large cohort research studies of BAT. Fat fraction (FF) and R2* maps were reconstructed from water-fat magnetic resonance imaging (MRI) of 25 subjects. A multi-atlas approach, based on atlases from nine subjects, was chosen as automated segmentation strategy. A semi-automated reference method was used to validate the automated method in the remaining subjects. Automated segmentations were obtained from a pipeline of preprocessing, affine registration, elastic registration and postprocessing. The automated method was validated with respect to segmentation overlap (Dice similarity coefficient, Dice) and estimations of FF, R2* and segmented volume. Bias in measurement results was also evaluated. Segmentation overlaps of Dice = 0.93 +/- 0.03 (mean +/- standard deviation) and correlation coefficients of r > 0.99 (P < 0.0001) in FF, R2* and volume estimates, between the methods, were observed. Dice and BMI were positively correlated (r = 0.54, P = 0.03) but no other significant bias was obtained (P >= 0.07). The automated method compared well with the reference method and can therefore be suitable for time-efficient and objective measurements in large cohort research studies of BAT.

    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Research subject
    Computerized Image Processing
    Identifiers
    urn:nbn:se:uu:diva-323968 (URN)10.1038/s41598-017-01586-7 (DOI)000402865000003 ()28596551 (PubMedID)
    Funder
    Swedish Research CouncilEU, FP7, Seventh Framework Programme, 279153
    Available from: 2017-06-08 Created: 2017-06-12 Last updated: 2019-04-15Bibliographically approved
    3. Brown adipose tissue estimated with the magnetic resonance imaging fat fraction is associated with glucose metabolism in adolescents
    Open this publication in new window or tab >>Brown adipose tissue estimated with the magnetic resonance imaging fat fraction is associated with glucose metabolism in adolescents
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:uu:diva-380052 (URN)
    Available from: 2019-03-22 Created: 2019-03-22 Last updated: 2019-04-29
    4. PET/MRI of glucose uptake, lipid content and perfusion in human brown adipose tissue
    Open this publication in new window or tab >>PET/MRI of glucose uptake, lipid content and perfusion in human brown adipose tissue
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:uu:diva-381764 (URN)
    Available from: 2019-04-15 Created: 2019-04-15 Last updated: 2019-04-29
  • 3.
    Lundström, Elin
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Strand, Robin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Johansson, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Bergsten, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Ahlström, Håkan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Kullberg, Joel
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Magnetic resonance imaging cooling–reheating protocol indicates decreased fat fraction via lipid consumption in suspected brown adipose tissue2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 4, article id e0126705Article in journal (Refereed)
    Abstract [en]

    OBJECTIVES: To evaluate whether a water-fat magnetic resonance imaging (MRI) cooling-reheating protocol could be used to detect changes in lipid content and perfusion in the main human brown adipose tissue (BAT) depot after a three-hour long mild cold exposure.

    MATERIALS AND METHODS: Nine volunteers were investigated with chemical-shift-encoded water-fat MRI at baseline, after a three-hour long cold exposure and after subsequent short reheating. Changes in fat fraction (FF) and R2*, related to ambient temperature, were quantified within cervical-supraclavicular adipose tissue (considered as suspected BAT, denoted sBAT) after semi-automatic segmentation. In addition, FF and R2* were quantified fully automatically in subcutaneous adipose tissue (not considered as suspected BAT, denoted SAT) for comparison. By assuming different time scales for the regulation of lipid turnover and perfusion in BAT, the changes were determined as resulting from either altered absolute fat content (lipid-related) or altered absolute water content (perfusion-related).

    RESULTS: sBAT-FF decreased after cold exposure (mean change in percentage points = -1.94 pp, P = 0.021) whereas no change was observed in SAT-FF (mean = 0.23 pp, P = 0.314). sBAT-R2* tended to increase (mean = 0.65 s-1, P = 0.051) and SAT-R2* increased (mean = 0.40 s-1, P = 0.038) after cold exposure. sBAT-FF remained decreased after reheating (mean = -1.92 pp, P = 0.008, compared to baseline) whereas SAT-FF decreased (mean = -0.79 pp, P = 0.008, compared to after cold exposure).

    CONCLUSIONS: The sustained low sBAT-FF after reheating suggests lipid consumption, rather than altered perfusion, as the main cause to the decreased sBAT-FF. The results obtained demonstrate the use of the cooling-reheating protocol for detecting changes in the cervical-supraclavicular fat depot, being the main human brown adipose tissue depot, in terms of lipid content and perfusion.

1 - 3 of 3
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  • nn-NO
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