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  • 1.
    Albano, Amanda
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Gustavsson, Sandra
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Echocardio-variability - Low and high frequency beat-to-beat variability in echocardiographic signals2013In: Computing in Cardiology 2013, 2013, p. 767-770, article id 6713490Conference paper (Refereed)
    Abstract [en]

    Measurement signals originating from the cardiovascular system are known to comprise oscillating components and beat-to-beat variability, e.g., heart-rate variability and blood pressure variability. In clinical echocardiographic procedures, typically only a few cardiac cycles are acquired. This pilot study analyses the beat-to-beat variability of echocardiographic variables (echocardio-variability) in minute long acquisitions. 

  • 2.
    Ali, Hazrat
    et al.
    Hamad Bin Khalifa University, Qatar Foundation, College of Science and Engineering, Doha, Qatar.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Shah, Zubair
    Hamad Bin Khalifa University, Qatar Foundation, College of Science and Engineering, Doha, Qatar.
    Leveraging GANs for data scarcity of COVID-19: Beyond the hype2023In: 2023 IEEE/CVF Conference on Computer Vision and Pattern Recognition Workshops (CVPRW), IEEE Computer Society, 2023, p. 659-667Conference paper (Refereed)
    Abstract [en]

    Artificial Intelligence (AI)-based models can help in diagnosing COVID-19 from lung CT scans and X-ray images; however, these models require large amounts of data for training and validation. Many researchers studied Generative Adversarial Networks (GANs) for producing synthetic lung CT scans and X-Ray images to improve the performance of AI-based models. It is not well explored how good GAN-based methods performed to generate reliable synthetic data. This work analyzes 43 published studies that reported GANs for synthetic data generation. Many of these studies suffered data bias, lack of reproducibility, and lack of feedback from the radiologists or other domain experts. A common issue in these studies is the unavailability of the source code, hindering reproducibility. The included studies reported rescaling of the input images to train the existing GANs architecture without providing clinical insights on how the rescaling was motivated. Finally, even though GAN-based methods have the potential for data augmentation and improving the training of AI-based models, these methods fall short in terms of their use in clinical practice. This paper highlights research hotspots in countering the data scarcity problem, identifies various issues as well as potentials, and provides recommendations to guide future research. These recommendations might be useful to improve acceptability for the GAN-based approaches for data augmentation as GANs for data augmentation are increasingly becoming popular in the AI and medical imaging research community.

  • 3.
    Ali, Hazrat
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Umander, Johannes
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Rohlén, Robin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    A Deep Learning Pipeline for Identification of Motor Units in Musculoskeletal Ultrasound2020In: IEEE Access, E-ISSN 2169-3536, Vol. 8, p. 170595-170608Article in journal (Refereed)
    Abstract [en]

    Skeletal muscles are functionally regulated by populations of so-called motor units (MUs). An MU comprises a bundle of muscle fibers controlled by a neuron from the spinal cord. Current methods to diagnose neuromuscular diseases and monitor rehabilitation, and study sports sciences rely on recording and analyzing the bio-electric activity of the MUs. However, these methods provide information from a limited part of a muscle. Ultrasound imaging provides information from a large part of the muscle. It has recently been shown that ultrafast ultrasound imaging can be used to record and analyze the mechanical response of individual MUs using blind source separation. In this work, we present an alternative method - a deep learning pipeline - to identify active MUs in ultrasound image sequences, including segmentation of their territories and signal estimation of their mechanical responses (twitch train). We train and evaluate the model using simulated data mimicking the complex activation pattern of tens of activated MUs with overlapping territories and partially synchronized activation patterns. Using a slow fusion approach (based on 3D CNNs), we transform the spatiotemporal image sequence data to 2D representations and apply a deep neural network architecture for segmentation. Next, we employ a second deep neural network architecture for signal estimation. The results show that the proposed pipeline can effectively identify individual MUs, estimate their territories, and estimate their twitch train signal at low contraction forces. The framework can retain spatio-temporal consistencies and information of the mechanical response of MU activity even when the ultrasound image sequences are transformed into a 2D representation for compatibility with more traditional computer vision and image processing techniques. The proposed pipeline is potentially useful to identify simultaneously active MUs in whole muscles in ultrasound image sequences of voluntary skeletal muscle contractions at low force levels.

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  • 4.
    Ali, Hazrat
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Department of Electrical and Computer Engineering, COMSATS University Islamabad, Abbottabad Campus, Abbottabad, Pakistan.
    Umander, Johannes
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Rohlén, Robin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Röhrle, Oliver
    Stuttgart Center for Simulation Technology (SC SimTech), University of Stuttgart, Stuttgart, Germany; Institute for Modelling and Simulation of Biomechanical Systems, Chair for Computational Biophysics and Biorobotics, University of Stuttgart, Stuttgart, Germany.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Modelling intra-muscular contraction dynamics using in silico to in vivo domain translation2022In: Biomedical engineering online, E-ISSN 1475-925X, Vol. 21, no 1, article id 46Article in journal (Refereed)
    Abstract [en]

    Background: Advances in sports medicine, rehabilitation applications and diagnostics of neuromuscular disorders are based on the analysis of skeletal muscle contractions. Recently, medical imaging techniques have transformed the study of muscle contractions, by allowing identifcation of individual motor units’ activity, within the whole studied muscle. However, appropriate image-based simulation models, which would assist the continued development of these new imaging methods are missing. This is mainly due to a lack of models that describe the complex interaction between tissues within a muscle and its surroundings, e.g., muscle fbres, fascia, vasculature, bone, skin, and subcutaneous fat. Herein, we propose a new approach to overcome this limitation.

    Methods: In this work, we propose to use deep learning to model the authentic intramuscular skeletal muscle contraction pattern using domain-to-domain translation between in silico (simulated) and in vivo (experimental) image sequences of skeletal muscle contraction dynamics. For this purpose, the 3D cycle generative adversarial network (cycleGAN) models were evaluated on several hyperparameter settings and modifcations. The results show that there were large diferences between the spatial features of in silico and in vivo data, and that a model could be trained to generate authentic spatio-temporal features similar to those obtained from in vivo experimental data. In addition, we used diference maps between input and output of the trained model generator to study the translated characteristics of in vivo data.

    Results: This work provides a model to generate authentic intra-muscular skeletal muscle contraction dynamics that could be used to gain further and much needed physiological and pathological insights and assess and overcome limitations within the newly developed research feld of neuromuscular imaging.

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  • 5.
    Bengtsson, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Family Medicine.
    Norberg, Margareta
    Umeå University, Faculty of Medicine, Department of Epidemiology and Global Health.
    Ng, Nawi
    Umeå University, Faculty of Medicine, Department of Epidemiology and Global Health. School of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
    Carlberg, Bo
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hultdin, Johan
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry.
    Lindahl, Bernt
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Sustainable Health.
    Lindahl, Bertil
    Department of Medical Sciences and Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden.
    Nordin, Steven
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyman, Emma
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Wennberg, Patrik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Family Medicine.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Näslund, Ulf
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    The beneficial effect over 3 years by pictorial information to patients and their physician about subclinical atherosclerosis and cardiovascular risk: results from the VIPVIZA randomized clinical trial2021In: American Journal of Preventive Cardiology, ISSN 2666-6677, Vol. 7, article id 100199Article in journal (Refereed)
    Abstract [en]

    Objective: Non-adherence to guidelines and preventive measures is a major challenge, particularly so to ob- tain long-term adherence to lifestyle changes and recommended medication. The objective was to investigate if pictorial information regarding subclinical carotid atherosclerosis provided to individuals and physicians gave sustained effects on cardiovascular risk beyond the previously reported effect after 1 year and up to 3 years. 

    Methods: A Prospective Randomized Open Blinded End-point (PROBE) trial. Within a CVD prevention program in Västerbotten County, Sweden, 3532 healthy individuals aged 40, 50 or 60 years were enrolled and 1:1 ran- domized to intervention ( n = 1749; pictorial information with additional prevention materials to participants and physicians) or control group ( n = 1783; no pictorial information to participants and physicians). Preventive measures were managed within primary care. Participants were investigated at baseline during 2013–2016 and at follow-up after 1 and 3 years. 

    Results: A beneficial effect on cardiovascular risk was observed at 3-year follow-up; Framingham Risk Score (FRS) was 13.38 for the intervention group and 14.08 for the control group ( p = 0.047) and SCORE was 1.69 vs. 1.82 ( p = 0.022). The effect observed at 1-year was sustained over 3 years after adjustment for sex and education and more pronounced among participants with a severe atherosclerotic picture at baseline.

    Conclusions: This study provides evidence of sustained beneficial effects on the adherence to prevention guidelines over 3 years of pictorial information about subclinical carotid atherosclerosis, resulting in lower cardiovascular risk regardless of sex and educational level. Direct visualization of the underlying still subclinical atherosclerotic disease, rather than just indirect information about risk factors and statistical risk of future myocardial infarction, stroke and death, is one way to tackle the problem of non-adherence to prevention of cardiovascular diseases.

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  • 6.
    Bengtsson, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Epidemiology and Global Health. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Nyman, Emma
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Näslund, Ulf
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Fhärm, Eva
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Family Medicine.
    Norberg, Margareta
    Umeå University, Faculty of Medicine, Department of Epidemiology and Global Health.
    Association of cardiovascular disease risk factors with combined carotid ultrasound measurements in subclinical atherosclerosisManuscript (preprint) (Other academic)
  • 7.
    Bengtsson, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Epidemiology and Global Health. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Family Medicine.
    Nyman, Emma
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Näslund, Ulf
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Fhärm, Eva
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Family Medicine.
    Norberg, Margareta
    Umeå University, Faculty of Medicine, Department of Epidemiology and Global Health.
    Multi-view carotid ultrasound is stronger associated with cardiovascular risk factors than presence of plaque or single carotid intima media thickness measurements in subclinical atherosclerosis2023In: The International Journal of Cardiovascular Imaging, ISSN 1569-5794, E-ISSN 1875-8312, Vol. 39, no 8, p. 1461-1471Article in journal (Refereed)
    Abstract [en]

    We aimed to explore the prevalence of atherosclerosis by using multi-view ultrasound examination of the carotid arteries and its association with clinical risk factors in a middle-aged population at low to intermediate risk of cardiovascular disease (CVD). Carotid vascular ultrasound was performed in 3532 participants in the VIPVIZA trial. Mean and maximal carotid intima media thickness (cIMT) at prespecified angles and plaque presence were examined on the left and right side. Associations between CVD risk factors and ultrasound variables were quantified by partial least squares (PLS) regression. A combined ultrasound variable was computed using weights of the first PLS component. Associations between CVD risk factors and the combined multi-view ultrasound variable, single cIMT and plaque measurements, respectively, were determined using linear regression modelling. The participants’ mean age was 55.7 years and 52.9% were women. Plaque prevalence was 51.1% in men and 39.0% in women. cIMT was higher in men than in women and in the left compared with the right carotid artery. The strongest association of CVD risk factors was observed with the combined multi-view ultrasound variable (R2 = 24%), compared with single cIMT variables (R2 = 14–18%) and plaque presence (R2 = 15%). The pattern was similar in both sexes. The association with CVD risk factors and the combined ultrasound variable was stronger in 40-year olds (R2 = 22%) compared with 50- or 60-year olds (R = 12%). CVD risk factors are stronger associated with a combined ultrasound variable than plaque presence or single cIMT measures suggesting that carotid multi-view ultrasonography better captures the focality of early atherosclerosis. Clinical Trial Registration: ClinicalTrials.gov, number NCT01849575. May 8, 2013.

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  • 8.
    Brändström, Helge
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Anaesthesiology.
    Grip, Helena
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Hallberg, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Ängquist, Karl-Axel
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
    Giesbrecht, Gordon G
    Hand cold recovery responses before and after 15 months of military training in a cold climate2008In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 79, no 9, p. 904-908Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: The ability of fingers to rapidly rewarm following cold exposure is a possible indicator of cold injury protection. We categorized the post-cooling hand-rewarming responses of men before and after participation in 15 mo of military training in a cold environment in northern Sweden to determine: 1) if the initial rewarming category was related to the occurrence of local cold injury during training; and 2) if cold training affected subsequent hand-rewarming responses. METHODS: Immersion of the dominant hand in 10 degrees C water for 10 min was performed pre-training on 77 men. Of those, 45 were available for successful post-training retests. Infrared thermography monitored the dorsal hand during 30 min of recovery. Rewarming was categorized as normal, moderate, or slow based on mean fingertip temperature at the end of 30 min of recovery (TFinger,30) and the percentage of time that fingertips were vasodilated (%VD). RESULTS: Cold injury occurrence during training was disproportionately higher in the slow rewarmers (four of the five injuries). Post-training, baseline fingertip temperatures and cold recovery variables increased significantly in moderate and slow rewarmers: TFinger30 increased from 21.9 +/- 4 to 30.4 +/- 6 degrees C (Moderate), and from 17.4 +/- 0 to 22.3 +/- 7 degrees C (Slow); %VD increased from 27.5 +/- 16 to 65.9 +/- 34% (Moderate), and from 0.7 +/- 2 to 31.7 +/- 44% (Slow). CONCLUSIONS: Results of the cold recovery test were related to the occurrence of local cold injury during long-term cold-weather training. Cold training itself improved baseline and cold recovery in moderate and slow rewarmers.

  • 9.
    Byenfeldt, Marie
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Department of Radiology in Östersund, Östersund, Sweden; Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden.
    Kihlberg, Johan
    Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden; Department of Radiology in Linköping, Linköping, Sweden.
    Nasr, Patrik
    Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden; Division of Diagnostics and Specialist Medicine, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Lindam, Anna
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Family Medicine.
    Bartholomä, Wolf C
    Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden; Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden.
    Lundberg, Peter
    Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden; Department of Radiation Physics, Linköping University, Linköping, Sweden; Department of Medical and Health Science in Linköping University, Linköping, Sweden.
    Ekstedt, Mattias
    Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden; Division of Diagnostics and Specialist Medicine, Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden.
    Altered probe pressure and body position increase diagnostic accuracy for men and women in detecting hepatic steatosis using quantitative ultrasound2024In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084Article in journal (Refereed)
    Abstract [en]

    Objectives: To evaluate the diagnostic performance of ultrasound guided attenuation parameter (UGAP) for evaluating liver fat content with different probe forces and body positions, in relation to sex, and compared with proton density fat fraction (PDFF).

    Methods: We prospectively enrolled a metabolic dysfunction-associated steatotic liver disease (MASLD) cohort that underwent UGAP and PDFF in the autumn of 2022. Mean UGAP values were obtained in supine and 30° left decubitus body position with normal 4 N and increased 30 N probe force. The diagnostic performance was evaluated by the area under the receiver operating characteristic curve (AUC).

    Results: Among 60 individuals (mean age 52.9 years, SD 12.9; 30 men), we found the best diagnostic performance with increased probe force in 30° left decubitus position (AUC 0.90; 95% CI 0.82–0.98) with a cut-off of 0.58 dB/cm/MHz. For men, the best performance was in supine (AUC 0.91; 95% CI 0.81–1.00) with a cut-off of 0.60 dB/cm/MHz, and for women, 30° left decubitus position (AUC 0.93; 95% CI 0.83–1.00), with a cut-off 0.56 dB/cm/MHz, and increased 30 N probe force for both genders. No difference was in the mean UGAP value when altering body position. UGAP showed good to excellent intra-reproducibility (Intra-class correlation 0.872; 95% CI 0.794–0.921).

    Conclusion: UGAP provides excellent diagnostic performance to detect liver fat content in metabolic dysfunction-associated steatotic liver diseases, with good to excellent intra-reproducibility. Regardless of sex, the highest diagnostic accuracy is achieved with increased probe force with men in supine and women in 30° left decubitus position, yielding different cut-offs.

    Clinical relevance statement: The ultrasound method ultrasound-guided attenuation parameter shows excellent diagnostic accuracy and performs with good to excellent reproducibility. There is a possibility to alter body position and increase probe pressure, and different performances for men and women should be considered for the highest accuracy.

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  • 10.
    Fortuin-de Smidt, Melony
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Bergman, Frida
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Hult, Andreas
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation.
    Norberg, Margareta
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Wennberg, Maria
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Wennberg, Patrik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Early adulthood exercise capacity, but not muscle strength, associates with subclinical atherosclerosis 40 years later in Swedish men2023In: European Journal of Preventive Cardiology, ISSN 2047-4873, E-ISSN 2047-4881, Vol. 30, no 5, p. 407-415Article in journal (Refereed)
    Abstract [en]

    AIMS: Poor exercise capacity and muscle strength in early adulthood are risk factors for cardiovascular disease (CVD). However, it is unclear how these factors relate to subclinical atherosclerosis due to a lack of longitudinal studies. This study investigated whether early adulthood exercise capacity and muscle strength associated with later adulthood subclinical atherosclerosis.

    METHODS AND RESULTS: This study included Swedish men (n = 797) who were eligible for military conscription (at ∼18-years of age) and who participated in the baseline assessment of the visualization of asymptomatic atherosclerotic disease for optimum cardiovascular prevention trial between 2013 and 2016 (at 60 years of age). At conscription, isometric muscle strength (dynamometer) and maximum exercise capacity (maximal load cycle ergometer test) were measured. During later adulthood (at 60 years old), the presence of carotid plaques and intima media thickness were measured by using high-resolution ultrasound. At follow-up, plaques were present in 62% (n = 493) of men. Exercise capacity in early adulthood associated with 19% lower odds of plaques [odds ratio (OR) 0.81, 95% confidence interval (CI) 0.68-0.96], independent of muscle strength. This association was not mediated by any single CVD risk factor. However, the total indirect effect of later, but not early, adulthood CVD risk factors was significant, while the direct effect was non-significant (OR 0.85, 95% CI 0.71-1.02). Associations between muscle strength and subclinical atherosclerosis were non-significant.

    CONCLUSION: Higher exercise capacity during early adulthood, but not muscle strength, may protect against carotid plaque development during adulthood mediated by the combination rather than a single later adulthood CVD risk factors.

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  • 11. Gerdle, Björn
    et al.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, Stefan J
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Holtermann, Andreas
    Roeleveld, Karin
    Altered neuromuscular control mechanisms of the trapezius muscle in fibromyalgia.2010In: BMC Musculoskeletal Disorders, E-ISSN 1471-2474, Vol. 11, p. 42-Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: fibromyalgia is a relatively common condition with widespread pain and pressure allodynia, but unknown aetiology. For decades, the association between motor control strategies and chronic pain has been a topic for debate. One long held functional neuromuscular control mechanism is differential activation between regions within a single muscle. The aim of this study was to investigate differences in neuromuscular control, i.e. differential activation, between myalgic trapezius in fibromyalgia patients and healthy controls. METHODS: 27 fibromyalgia patients and 30 healthy controls performed 3 minutes bilateral shoulder elevations with different loads (0-4 Kg) with a high-density surface electromyographical (EMG) grid placed above the upper trapezius. Differential activation was quantified by the power spectral median frequency of the difference in EMG amplitude between the cranial and caudal parts of the upper trapezius. The average duration of the differential activation was described by the inverse of the median frequency of the differential activations. RESULTS: the median frequency of the differential activations was significantly lower, and the average duration of the differential activations significantly longer in fibromyalgia compared with controls at the two lowest load levels (0-1 Kg) (p < 0.04), but not at the two highest load levels (2 and 4 Kg). CONCLUSION: these findings illustrate a different neuromuscular control between fibromyalgia patients and healthy controls during a low load functional task, either sustaining or resulting from the chronic painful condition. The findings may have clinical relevance for rehabilitation strategies for fibromyalgia.

  • 12. Gerdle, Björn
    et al.
    Östlund, Nils
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Grönlund, Christer
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Roeleveld, Karin
    Karlsson, Stefan
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Firing rate and conduction velocity of single motor units in the trapezius muscle in fibromyalgia patients and healthy controls2008In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 18, no 5, p. 707-716Article in journal (Refereed)
    Abstract [en]

    Fibromyalgia is a common chronic pain condition in the population (2-4%), which often is associated with prominent negative consequences with respect to participation in daily activities. There are several reports in the literature concerning the effects of acute experimental pain on motor control. However, a more heterogeneous picture exists in the literature with respect to whether chronic pain conditions affect motor control. This study compares firing rate and conduction velocity (CV) of single motor units (MUs) in the trapezius muscle of fibromyalgia patients (FM) and healthy controls (CON). Multi-channel surface electromyography was used to estimate both MU firing rate and CV because this technique allows simultaneous estimation of both these variables and the measurements are easy and non-invasive. In this study, 29 FM and 30 CON subjects participated and performed isometric shoulder elevations using weights up to 4 kg. No significant differences in the firing rate of MUs in the trapezius muscle were found between the FM and CON groups (95% confidence interval was -1.9 and 1.3 pulses per second). There were no significant differences in CV between the groups at 1 and 2 kg load. However, the FM group had significantly higher CV in contractions without external load (p=0.004). We were unable to confirm the pain-adaptation model since no differences in firing rate between the two groups were found. CV was significantly higher in FM than in healthy controls; this might be due to alterations in histopathology and microcirculation.

  • 13.
    Granåsen, Gabriel
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, Markus
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. marcus.karlsson@regionvasterbotten.se.
    Westermark, Per
    Institutionen för immunologi, genetik och patologi, Uppsala universitet.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Suhr, Ole B.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Multimodal analysis of the pattern of disturbances in heart rate variability and echocardiographic features in patients with hereditary transthyretin amyloidosis and hypertrophic cardiomyopathyManuscript (preprint) (Other academic)
  • 14.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Spatio-temporal processing of surface electromyographic signals: information on neuromuscular function and control2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    During muscle contraction, electrical signals are generated by the muscle cells. The analysis of those signals is called electromyography (EMG). The EMG signal is mainly determined by physiological factors including so called central factors (central nervous system origin) and peripheral factors (muscle tissue origin). In addition, during the acquisition of EMG signals, technical factors are introduced (measurement equipment origin). The aim of this dissertation was to develop and evaluate methods to estimate physiological properties of the muscles using multichannel surface EMG (MCsEMG) signals.

    In order to obtain accurate physiological estimates, a method for automatic signal quality estimation was developed. The method’s performance was evaluated using visually classified signals, and the results demonstrated high classification accuracy.

    A method for estimation of the muscle fibre conduction velocity (MFCV) and the muscle fibre orientation (MFO) was developed. The method was evaluated with synthetic signals and demonstrated high estimation precision at low contraction levels.

    In order to discriminate between the estimates of MFCV and MFO belonging to single or populations of motor units (MUs), density regions of so called spatial distributions were examined. This method was applied in a study of the trapezius muscle and demonstrated spatial separation of MFCV (as well as MFO) even at high contraction levels.

    In addition, a method for quantification of MU synchronisation was developed. The performance on synthetic sEMG signals showed high sensitivity on MU synchronisation and robustness to changes in MFCV. The method was applied in a study of the biceps brachii muscle and the relation to force tremor during fatigue. The results showed that MU synchronisation accounted for about 40 % of the force tremor.

    In conclusion, new sEMG methods were developed to study muscle function and motor control in terms of muscle architecture, muscle fibre characteristics, and processes within the central nervous system.

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  • 15.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Albano, Amanda
    Gustavsson, Sandra
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Wiklund, Urban
    Henein, Michael Y
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology.
    Significant beat-to-beat variability of E/e’ irrespective of respiration2013In: International cardiovascular forum, ISSN 2409-3424, Vol. 1, no 2, p. 88-89Article in journal (Refereed)
    Abstract [en]

    The E/e’ ratio is commonly used in Doppler echocardiographic examinations to estimate the pulmonary capillary wedge pressure. The rationale of using this ratio is to combine left ventricular (LV) filling (E) and relaxation (e’) velocities to indirectly assess left atrial pressure. However, the accuracy of this index has recently been questioned, particularly in patients with controlled heart failure. Likewise, the potential beat-to-beat variability of such measurements remains undetermined. The cardiovascular system is subject to several oscillations with the potential of influencing LV function and its intra-cavitary pressures, hence measurements of its filling and relaxation velocities. The aim of this pilot study was to assess the beat-to-beat variability of the E/e’ ratio in one minute long examination in healthy subjects, and patients with various severity of amyloid heart disease. The results show that despite critical application of the standard echocardiographic recording recommendations, E/e’ beat-to-beat variability was 36 % (22 to 50%) in healthy subjects and 17 % (11-26%) in patients, and where the most severe amyloid heart disease had the least variability. Thus, clinical use of a single or few cardiac beats might not necessarily reflect an accurate ratio between the two velocities, and hence casts doubt over their diagnostic value.

  • 16.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Claesson, Kenji
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    D'hooge, Jan
    Department of Cardiovascular sciences, Leuven, Belgium.
    Henein, Michael Y.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology. Umeå Heart Centre.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology. Umeå Heart Centre.
    Simultaneous quantification of myocardial and blood flow velocities based on duplex mode ultrasound imaging2013In: Biomedical engineering online, E-ISSN 1475-925X, Vol. 12, article id 107Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Ultrasound imaging of the heart is a commonly used clinical tool to assess cardiac function. The basis for this analysis is the quantification of cardiac blood flow and myocardial velocities. These are typically measured using different imaging modes and on different cardiac cycles. However, due to beat-to-beat variations such as irregular heart rhythm and transient events, simultaneous acquisition is preferred. There exists specialized ultrasound systems for this purpose; however, it would be beneficial if this could be achieved using conventional ultrasound systems due to their wide availability. The conventional Duplex mode ultrasound allows simultaneous acquisition, however at a highly reduced spatial and temporal resolution.

    METHODS: The aim of this work was to present and evaluate the performance of a novel method to recover myocardial tissue velocity using conventional Duplex ultrasound imaging, and to demonstrate its feasibility for the assessment of simultaneous blood flow and myocardial velocity in-vivo. The essence of the method was the estimation of the axial phase shift of robust echogenic structures between subsequent image frames. The performance of the method was evaluated on synthetic tissue mimicking B-mode image sequences at different frame rates (20--60 Hz) and tissue velocities (peak velocities 5-15cm/s), using cardiac deformation and displacement characteristics. The performance was also compared to a standard 2-D speckle tracking technique.

    RESULTS: The method had an overall high performance at frame rates above 25 Hz, with less than 15% error of the peak diastolic velocity, and less than 10 ms peak timing error. The method showed superior performance compared to the 2-D tracking technique at frame rates below 50 Hz. The in-vivo quantification of simultaneous blood flow and myocardial tissue velocities verified the echocardiographic patterns and features of healthy subjects and the specific patient group.

    CONCLUSIONS: A novel myocardial velocity quantification method was presented and high performance at frame rates above 25Hz was shown. In-vivo quantification of simultaneous myocardial and blood flow velocities was feasible using the proposed method and conventional Duplex mode imaging. We propose that the methodology is suitable for retrospective as well as prospective studies on the mechanics and hemodynamics of the heart.

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  • 17.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Claesson, Kenji
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Holtermannz, Andreas
    Imaging two-dimensional mechanical waves of skeletal muscle contraction2013In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 39, no 2, p. 360-369Article in journal (Refereed)
    Abstract [en]

    Skeletal muscle contraction is related to rapid mechanical shortening and thickening. Recently, specialized ultrasound systems have been applied to demonstrate and quantify transient tissue velocities and one-dimensional (1-D) propagation of mechanical waves during muscle contraction. Such waves could potentially provide novel information on musculoskeletal characteristics, function and disorders. In this work, we demonstrate two-dimensional (2-D) mechanical wave imaging following the skeletal muscle contraction. B-mode image acquisition during multiple consecutive electrostimulations, speckle-tracking and a time-stamp sorting protocol were used to obtain 1.4 kHz frame rate 2-D tissue velocity imaging of the biceps brachii muscle contraction. The results present novel information on tissue velocity profiles and mechanical wave propagation. In particular, counter-propagating compressional and shear waves in the longitudinal direction were observed in the contracting tissue (speed 2.8-4.4 m/s) and a compressional wave in the transverse direction of the non-contracting muscle tissue (1.2-1.9 m/s). In conclusion, analysing transient 2-D tissue velocity allows simultaneous assessment of both active and passive muscle tissue properties. (E-mail: christer.gronlund@vll.se) (C) 2013 World Federation for Ultrasound in Medicine & Biology.

  • 18.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Holtermann, A
    Roeleveld, K
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Quantification of motor unit synchronization from surface EMG signals with minimized dependency on muscle fibre conduction velocityManuscript (preprint) (Other academic)
  • 19.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Holtermann, Andreas
    Roeleveld, Karin
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Motor unit synchronization during fatigue: a novel quantification method.2009In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 19, no 2, p. 242-251Article in journal (Refereed)
    Abstract [en]

    Motor unit (MU) synchronization is the result of commonality in the pre-synaptic input to MUs. Previously proposed techniques to estimate MU synchronization based on invasive and surface electromyography (sEMG) recordings have been, respectively, limited by the analyzed MU population size and influence of changes in muscle fibre conduction velocities (MFCVs). The aim of this paper was to evaluate a novel descriptor of MU synchronization on a large MU population, and to minimize its dependency on MFCV. The method is based on the asymmetry of MU action potentials, causing synchronized MU action potentials to skew the monopolar sEMG signal distribution. The descriptor was the skewness statistic used on sub-band filtered monopolar sEMG signals (sub-band skewness). The method was evaluated using simulated signals and its performance was evaluated in terms of bias and sensitivity of the sub-band skewness quantifying the MU synchronization level. The best sensitivity was obtained using sub-band filtering at scale 5 (Mexican hat wavelet). The sensitivity was in general about 0.1units per 5% MU synchronization level. Changes in MFCV had a minimal influence, and caused at most a 5% deviant MU synchronization quantification level. A halved recruitment level had higher bias and a 20% lower sensitivity. Increased firing rate (14-34Hz) reduced the sensitivity about 50%. The sensitivity of the descriptor was robust to noise, and different volume conduction properties. It should be noted that the sub-band skewness comprises a subject-dependent component implying that only changes in MU synchronization level can be quantified.

  • 20.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Roeleveld, Karin
    Holtermann, Andreas
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    On-line signal quality estimation of multichannel surface electromyograms2005In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, no 3, p. 357-364Article in journal (Refereed)
  • 21.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Rohlén, Robin
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Department of Biomedical Engineering, Lund University, Lund, Sweden.
    Ultrafast ultrasound imaging can be used to access single motor units in deep muscles, but the underlying biomechanical source remains to be understood2023In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 71, article id 102797Article in journal (Refereed)
  • 22.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Östlund, Nils
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindh, Jack
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Bergström, Per
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Oncology.
    Karlsson, Stefan J
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Spatio-temporal processing of surface EMG signals from the sternocleidomastoideus muscle to assess effects of radiotherapy on motor unit conduction velocity and firing rate: a pilot study2008In: Biomedical Signal Processing and Control, ISSN 1746-8094, Vol. 3, no 2, p. 163-168Article in journal (Refereed)
    Abstract [en]

    Radiation therapy causes both muscle and nerve tissue damage. However, the evolution and mechanisms of these damages are not fully understood. Information on the state of active muscle fibres and motoneurons can be obtained by measuring sEMG signals and calculating the conduction velocity (CV) and firing rate of individual motor units, respectively. The aim of this pilot study was to evaluate if the multi-channel surface EMG (sEMG) technique could be applied to the sternocleidomastoideus muscle (SCM) of radiotherapy patients, and to assess if the CV and firing rate are altered as a consequence of the radiation.

    Surface EMG signals were recorded from the radiated and healthy SCM muscles of 10 subjects, while subjects performed isometric rotation of the head. CV and firing rate were calculated using two recently proposed methods based on spatio-temporal processing of the sEMG signals. The multi-channel sEMG technique was successfully applied to the SCM muscle and CV and firing rates were obtained. The measurements were fast and simple and comfortable for the patients. Sufficient data quality was obtained from both sides of seven and four subjects for the CV and firing rate analysis, respectively. No differences in CV or firing rate were found between the radiated and non-radiated sides (p = 0.13 and p = 0.20, respectively). Firing rate and CV were also obtained from a myokymic discharge pattern. It was found that the CV decreased significantly (p = 0.01) during the bursts.

  • 23.
    Grönlund, Christer
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Östlund, Nils
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Roeleveld, Karin
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Simultaneous estimation of muscle fibre conduction velocity and muscle fibre orientation using 2D multichannel surface electromyogram2005In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, no 1, p. 63-70Article in journal (Refereed)
  • 24.
    Gustafsson, Sandra
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Granåsen, Gabriel
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Suhr, Ole B.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology.
    Discriminating hereditary transthyretin cardiomyopathy from hypertrophic cardiomyopathy using an echocardiographic and ECG based classification tree2014In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 35, no Supplement 1, Meeting abstract P5254, p. 929-929Article in journal (Other academic)
  • 25.
    Gustafsson, Sandra
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology. Umeå Heart Centre.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Mörner, Stellan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology. Umeå Heart Centre.
    Suhr, Ole
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology. Umeå Heart Centre.
    Can echocardiography differentiate hereditary transthyretin amyloidosis from hypertrophic cardiomyopathy?2013In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 34, no Supplement: 1, p. 213-213Article in journal (Other academic)
    Abstract [en]

    Purpose: Hereditary transthyretin amyloidosis (ATTR) andhypertrophic cardiomyopathy (HCM) have many phenotypic similarities when examined by echocardiography. As the two conditions have different treatment strategies it is of importance to accurately diagnose these patients early in the disease. This study aimed to identify the most accurate echocardiographic method in differentiating these two conditions by using traditional and speckle tracking echocardiographyas well as myocardial texture analysis.

    Methods: We investigated 40 healthy controls, 33 patients with biopsy proven ATTR and 20 with HCM. All patients had septal thickness >12 mm. We measured left ventricular (LV) global strain as intrinsic systolic function and LV E/e' to estimate filling pressures. We also tested septal cyclic integrated backscatter (cIBS) and septal entropy as both being measures for myocardial highly reflection pattern whereas cIBS showing motion of highly reflective echoes and entropy the distribution of highly reflective echoes.

    Results: LV global strain, cIBS and E/e' were not useful in differentiating ATTR from HCM. However, septal entropy was found to be significantly different and showed an area under the curve from ROC analysis of 0.66 separating ATTR from HCM.

    Conclusion: After using detailed analysis of different aspects of LV morphology and function we found that myocardial texture behavior from entropy analysis was the only method useful in differentiating patients with ATTR fromHCM.

  • 26.
    Gustavsson, Sandra
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Granåsen, Gabriel
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Mörner, Stellan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Henein, Michael
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Suhr, Ole B
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Can echocardiography and ECG discriminate hereditary transthyretin V30M amyloidosis from hypertrophic cardiomyopathy?2015In: Amyloid: Journal of Protein Folding Disorders, ISSN 1350-6129, E-ISSN 1744-2818, Vol. 22, no 3, p. 163-170Article in journal (Refereed)
    Abstract [en]

    Objective: Hereditary transthyretin (ATTR) amyloidosis with increased left ventricular wall thickness could easily be misdiagnosed by echocardiography as hypertrophic cardiomyopathy (HCM). Our aim was to create a diagnostic tool based on echocardiography and ECG that could optimise identification of ATTR amyloidosis. Methods: Data were analysed from 33 patients with biopsy proven ATTR amyloidosis and 30 patients with diagnosed HCM. Conventional features from ECG were acquired as well as two dimensional and Doppler echocardiography, speckle tracking derived strain and tissue characterisation analysis. Classification trees were used to select the most important variables for differentiation between ATTR amyloidosis and HCM. Results: The best classification was obtained using both ECG and echocardiographic features, where a QRS voltage >30 mm was diagnostic for HCM, whereas in patients with QRS voltage <30 mm, an interventricular septal/posterior wall thickness ratio (IVSt/PWt) >1.6 was consistent with HCM and a ratio <1.6 supported the diagnosis of ATTR amyloidosis. This classification presented both high sensitivity (0.939) and specificity (0.833). Conclusion: Our study proposes an easily interpretable classification method for the differentiation between HCM and increased left ventricular myocardial thickness due to ATTR amyloidosis. Our combined echocardiographic and ECG model could increase the ability to identify ATTR cardiac amyloidosis in clinical practice.

  • 27.
    Henein, Mark
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Tossavainen, Erik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Söderberg, Stefan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Gonzalez, Manuel
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Left atrial strain rate estimates PCWP2013In: International cardiovascular forum, ISSN 2409-3424, no 1, p. 25-30Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: Raised left atrial (LA) pressure is a common pathway for many pathologies and is known for its complications. It has a direct effect on LA cavity size and potentially also its function. We hypothesized that raised LA pressure, as shown by pulmonary capillary wedge pressure (PCWP), correlates with severity of global LA deformation abnormalities during atrial systole (LASRa). DESIGN AND PATIENTS: We prospectively studied 46 consecutive patients, mean age 61 ±13 years, 17 males, of various etiologies who underwent right heart catheterization and simultaneous Doppler echocardiography using spectral, tissue Doppler and speckle tracking echocardiography techniques for assessing LA structure and function. RESULTS: PCWP correlated with direct measurements of LA structure and function: LA volume (r= 0.43, p<0.01) and LASRa (r=0.79, p<0.001). PCWP correlated also with other indirect measures of LA pressure such as E/A (r=0.65, p<0.001), E wave deceleration time (r=0.54, p<0.001), E/e’ (r=0.49, p<0.001) and LA systolic filling fraction (r=0.52, p<0.001). However, LASRa together with LA systolic filling fraction, had the highest areas under the curve (0.83 and 0.87, respectively) for identifying patients with PCWP > 15 mmHg. CONCLUSION: PCWP correlates with LA deformation rate during atrial systole and to a higher extent than conventional Doppler measures of raised LA pressures. These findings should have significant clinical implications in correctly identifying breathless patients due to raised LA pressure.

  • 28.
    Henein, Michael Y
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Tossavainen, Erik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Söderberg, Stefan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Gonzalez, Manuel
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology.
    Right and left heart dysfunction predict mortality in pulmonary hypertension2017In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 37, no 1, p. 45-51Article in journal (Refereed)
    Abstract [en]

    In pulmonary hypertension (PH), the right heart dysfunction is a strong predictor of adverse clinical outcome, while the role of the left heart is not fully determined. The aim of this study was to identify predictors of mortality in precapillary PH including measures of both right and left heart function. We studied 34 patients (mean age 64 ± 13, range 31-82 years, 24 females) with precapillary PH, all of whom underwent detailed Doppler echocardiographic examination of the right and left heart function using conventional and speckle-tracking echocardiography. Patients were followed up for up to 8 years (mean 4·2 ± 1·9 years). At follow-up, 16 patients survived. Left ventricular (LV) filling time (P = 0·007), pulmonary artery acceleration time (P = 0·009), right atrial pressure (RAP) (P<0·001) and tricuspid regurgitation (TR) severity (P = 0·007) were worse in the deceased group. RV global longitudinal strain (GLS) (P = 0·001), RAP (P≤0·001), LV filling time (P<0·001) and TR severity (P<0·001) were the most accurate predictors, having the largest AUC (>0·65) and carried the highest risk for mortality (P<0·001 for all). The strongest predictors of mortality in precapillary PH indirectly reflect both left and right heart dysfunction including atrial structure and function disturbances. While an interaction pattern is observed, it needs to be confirmed in a larger cohort.

  • 29.
    Holtermann, A
    et al.
    Human Movement Sciences Programme, Norwegian University of Science and Technology, Trondheim, Norway.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Ingebrigtsen, J
    Human Movement Sciences Programme, Norwegian University of Science and Technology, Trondheim, Norway.
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Roeleveld, K
    Human Movement Sciences Programme, Norwegian University of Science and Technology, Trondheim, Norway.
    Duration of differential activations is functionally related to fatigue prevention during low-level contractions.2010In: Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, ISSN 1873-5711, Vol. 20, no 2, p. 241-245Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the importance of duration of differential activations between the heads of the biceps brachii on local fatigue during prolonged low-level contractions. Fifteen subjects carried out isometric elbow flexion at 5% of maximal voluntary contraction (MVC) for 30 min. MVCs were performed before and at the end of the prolonged contraction. Surface electromyographic (EMG) signals were recorded from both heads of the biceps brachii. Differential activation was analysed based on the difference in EMG amplitude (activation) between electrodes situated at the two heads. Differential activations were quantified by the power spectral median frequency of the difference in activation between the heads throughout the contraction. The inverse of the median frequency was used to describe the average duration of the differential activations. The relation between average duration of the differential activations and the fatigue-induced reduction in maximal force was explored by linear regression analysis. The main finding was that the average duration of differential activation was positively associated to relative maximal force at the end of the 30 min contraction (R(2)=0.5, P<0.01). The findings of this study highlight the importance of duration of differential activations for local fatigue, and support the hypothesis that long term differential activations prevent fatigue during prolonged low-level contractions.

  • 30. Holtermann, A.
    et al.
    Grönlund, Christer
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Karlsson, J. Stefan
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Roeleveld, Karin
    Differential activation of regions within the biceps brachii muscle during fatigue2008In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 192, no 4, p. 559-567Article in journal (Refereed)
    Abstract [en]

    Aim: To examine the occurrence of repeated differential activation between the heads of the biceps brachii muscle and its relation to fatigue prevention during a submaximal contraction.

    Methods: Thirty‐nine subjects carried out an isometric contraction of elbow flexion at 25% of maximal voluntary contraction (MVC) until exhaustion. A grid of 13 by 10 electrodes was used to record surface electromyographic signals from both heads of the biceps brachii. The root‐mean‐square of signals recorded from electrodes located medially and laterally was used to analyse activation differences. Differential activation was defined as periods of 33% different activation level between the two heads of the biceps brachii muscle.

    Results: Differential muscle activation was demonstrated in 30 of 33 subjects with appropriate data quality. The frequency of differential activation increased from 4.9 to 6.6 min−1 at the end of the contractions with no change in duration of the differential activations (about 1.4 s). Moreover, the frequency of differential activation was, in general, negatively correlated with time to exhaustion.

    Conclusion: The observed differential activation between the heads of the biceps brachii can be explained by an uneven distribution of synaptic input to the motor neurone pool. The findings of this study indicate that differential activation of regions within a muscle does not prevent fatigue at a contraction level of 25% of MVC.

  • 31. Holtermann, Andreas
    et al.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Roeleveld, Karin
    Motor unit synchronization during fatigue: described with a novel sEMG method based on large motor unit samples.2009In: Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, ISSN 1873-5711, Vol. 19, no 2, p. 232-241Article in journal (Refereed)
    Abstract [en]

    The amount of documented increase in motor unit (MU) synchronization with fatigue and its possible relation with force tremor varies largely, possibly due to inhomogeneous muscle activation and methodological discrepancies and limitations. The aim of this study was to apply a novel surface electromyographical (EMG) descriptor for MU synchronization based on large MU populations to examine changes in MU synchronization with fatigue at different sites of a muscle and its relation to tremor. Twenty-four subjects performed an isometric elbow flexion at 25% of maximal voluntary contraction until exhaustion. Monopolar EMG signals were recorded using a grid of 130 electrodes above the biceps brachii. Changes in MU synchronization were estimated based on the sub-band skewness of EMG signals and tremor by the coefficient of variation in force. The synchronization descriptor was dependent on recording site and increased with fatigue together with tremor. There was a general association between these two parameters, but not between their fluctuations. These results are in agreement with other surface EMG studies and indicate that the novel descriptor can be used to attain information of synchronization between large MU populations during fatigue that cannot be retrieved with intra-muscular EMG.

  • 32. Holtermann, Andreas
    et al.
    Grönlund, Christer
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Karlsson, Stefan
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF). Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Roeleveld, Karin
    Spatial distribution of active muscle fibre characteristics in the upper trapezius muscle and its dependency on contraction level and duration2008In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 18, no 3, p. 372-381Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to provide direct in vivo information of the physiological and structural characteristics of active muscle fibres from a large part of the upper trapezius muscle. Two-dimensional (2-D) multi-channel surface electromyography recordings were used, with 13 × 10 electrodes covering 6 × 4.5 cm of the skin’s surface. A previously developed method was applied to detect individual propagating motor unit action potentials and to estimate their corresponding muscle fibre conduction velocity (MFCV) and muscle fibre orientation (MFO). Using these estimates, spatial distributions of MFCV and MFO were examined for five male subjects performing isometric shoulder elevation at different force levels. The main results were: (1) the general relationship between MFCV and force generation was non-systematic, with a positive relationship at the inferior part of the muscle, (2) the spatial distribution of MFCV at different force levels and fatigue was inhomogeneous and (3) the MFO was slightly different (6°) of the muscle fibres with origin superior compared to inferior to the C7 vertebra. These findings provide new information of the MFO of contracting muscle fibres and knowledge of the physiological characteristics of a large part of the upper trapezius muscle that previously was based on observations from human cadavers only.

  • 33. Holtermann, Andreas
    et al.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Roeleveld, Karin
    Gerdle, Björn
    The relation between neuromuscular control and pain intensity in fibromyalgia2011In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 21, no 3, p. 519-524Article in journal (Refereed)
    Abstract [en]

    Fibromyalgia patients are shown to have a different neuromuscular control (differential activation) than healthy persons. Before clinical trials can be initiated, the relation between differential activations and pain intensity among fibromyalgia patients needs to be investigated. Twenty-seven fibromyalgia patients performed 3 min bilateral shoulder elevations with different loads (0-4 kg) with a high-density surface electromyographical (EMG) grid placed on the upper trapezius. Differential activation was quantified by the power spectral median frequency of the difference in EMG amplitude between the cranial and caudal parts of the upper trapezius. The average duration of the differential activation was described by the inverse of the median frequency of the differential activations. The relation between frequency and duration of differential activations as an average of the 4 loads and pain intensity the same day prior to the experiment was explored by Pearson's correlation coefficients. A strong negative relation between frequency of differential activations and pain intensity (R=-0.67, p<0.001) and a strong positive association between duration of differential activations and pain intensity (R=0.66, p<0.001) were found. The significant association between frequency and duration of differential activations and pain intensity among the fibromyalgia patients indicates a relation between this neuromuscular control pattern and pain intensity. This finding support initiation of clinical trials for investigating effects on pain intensity of modifying differential activations among fibromyalgia patients.

  • 34. Holtermann, Andreas
    et al.
    Roeleveld, Karin
    Mork, Paul Jarle
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Andersen, Lars L
    Olsen Baare, Henrik
    Zebis Kreutzfeldt, Mette
    Sjøgaard, Gisela
    Søgaard, Karen
    Selective activation of neuromuscular compartments within the human trapezius muscle.2009In: Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, ISSN 1873-5711, Vol. 19, no 5, p. 896-902Article in journal (Refereed)
    Abstract [en]

    Task-dependent differences in relative activity between "functional" subdivisions within human muscles are well documented. Contrary, independent voluntary control of anatomical subdivisions, termed neuromuscular compartments is not observed in human muscles. Therefore, the main aim of this study was to investigate whether subdivisions within the human trapezius can be independently activated by voluntary command using biofeedback guidance. Bipolar electromyographical electrodes were situated on four subdivisions of the trapezius muscle. The threshold for "active" and "rest" for each subdivision was set to >12% and <1.5% of the maximal electromyographical amplitude recorded during a maximal voluntary contraction. After 1h with biofeedback from each of the four trapezius subdivisions, 11 of 15 subjects learned selective activation of at least one of the four anatomical subdivisions of the trapezius muscle. All subjects managed to voluntarily activate the lower subdivisions independently from the upper subdivisions. Half of the subjects succeeded to voluntarily activate both upper subdivisions independently from the two lower subdivisions. These findings show that anatomical subdivisions of the human trapezius muscle can be independently activated by voluntary command, indicating neuromuscular compartmentalization of the trapezius muscle. The independent activation of the upper and lower subdivisions of the trapezius is in accordance with the selective innervation by the fine cranial and main branch of the accessory nerve to the upper and lower subdivisions. These findings provide new insight into motor control characteristics, learning possibilities, and function of the clinically relevant human trapezius muscle.

  • 35.
    Ibrahimi, Pranvera
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Jashari, Fisnik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Johansson, Elias
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine. Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Bajraktari, Gani
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Henein, Michael Y.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Common carotid intima-media features determine distal disease phenotype and vulnerability in asymptomatic patients2015In: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 196, p. 22-28Article in journal (Refereed)
    Abstract [en]

    Objectives: There is a growing awareness of the importance of carotid plaque features evaluation in stroke prediction. Carotid intima-media thickness (IMT) and recently its echogenicity were used for stroke prediction, although their clinical relevance was not well determined. The aim of this study was to assess the relationship between common carotid artery (CCA) ultrasound markers of atherosclerosis and distal, bifurcation and internal carotid artery (ICA), plaque features. Methods: We analyzed 137 carotid arteries in 87 asymptomatic patients with known carotid disease (mean age 69 +/- 6 year, 34.5% females). Intima media thickness (IMT) and its gray scale median (IM-GSM) were measured at the CCA. Plaque textural features including gray scale median (GSM), juxtaluminal black area (JBA-mm(2)) without a visible cap, and plaque coarseness, at bifurcation and ICA were also determined. CCA measurements were correlated with those of the distal plaques. Results: An increased IMT in CCA correlated with plaque irregularities in the bifurcation and ICA (r = 0.53, p < 0.001), while IM-GSM was closely related to plaque echogenicity (GSM) (r = 0.76, p < 0.001), and other textural plaque features. Both, IMT and IM-GSM correlated weakly with stenosis severity (r = 0.27, p = 0.001 and r = -0.18, p = 0.026) respectively. Conclusion: In asymptomatic patients, measurements of CCA reflect distal, bifurcation and ICA disease, with IMT reflecting plaque irregularities and IM-GSM as markers of textural plaque abnormalities. Integrating measurements of both IMT and IM-GSM in a model could be used as a better marker of disease vulnerability over and above each measure individually. 

  • 36.
    Ibrahimi, Pranvera
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Jashari, Fisnik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Johansson, Elias
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Bajraktari, Gani
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Henein, Michael Y
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Vulnerable plaques in the contralateral carotid arteries in symptomatic patients: a detailed ultrasound analysis2014In: Atherosclerosis, ISSN 0021-9150, E-ISSN 1879-1484, Vol. 235, no 2, p. 526-531Article in journal (Refereed)
    Abstract [en]

    BACKGROUND AND AIM: Carotid plaques may represent a generalized atherosclerotic syndrome or a localized disease. The aim of this study was to assess the morphological and textural features of carotid plaques located contralateral to the symptomatic side and compare them with the symptomatic side and with plaques from asymptomatic patients. METHODS: We studied 66 arteries in 39 patients (mean age 70 ± 7 year, 33% females). Arterial plaques were classified as either symptomatic (n = 30), contralateral to symptomatic (n = 25) or asymptomatic (n = 11). We compared several plaque features between these groups including the mean values of the grey scale median (GSM), entropy, juxtaluminal black area (JBA) without visible echogenic cap, GSM of the JBA and surface irregularity. RESULTS: The plaques contralateral to symptomatic arteries had similar morphological and textural features to those in the symptomatic arteries. In contrast, they had more vulnerable morphological and textural features than those in asymptomatic arteries: less smooth plaques (12% vs. 55%) and instead more often mildly irregular (60% vs 36%) or markedly irregular (28% vs. 9%; p = 0.03), lower GSM (26.2 ± 8 vs. 49.4 ± 14, p < 0.001) and lower GSM of the JBA (5.0 ± 3.6 vs. 11.4 ± 2.1, p = 0.008). The frequency of entropy and plaque calcification was similar in all groups. CONCLUSION: Symptomatic patients with carotid artery disease seem to have similar morphological and textural features of vulnerability in the symptomatic and the contralateral carotid arteries, which are profound compared with asymptomatic carotid arteries. These findings support the concept of generalized carotid atherosclerotic pathology rather than incidental unilateral disease, and also emphasize a need for aggressive measures for plaque stabilization, particularly in symptomatic patients.

  • 37.
    Ibrahimi, Pranvera
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Jashari, Fisnik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Johansson, Elias
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Henein, Michael Y.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Common carotid intima-media measurements determine distal disease structure and vulnerability in asymptomatic patients2015In: Atherosclerosis, ISSN 0021-9150, E-ISSN 1879-1484, Vol. 241, no 1, p. E164-E164Article in journal (Other academic)
  • 38.
    Jashari, Fisnik
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Ibrahimi, Pranvera
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Bajraktari, Gani
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine. Department of Clinical Sciences, Danderyds Hospital, Karolinska Institute, Stockholm, Sweden.
    Henein, Michael Y
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Carotid plaque echogenicity predicts cerebrovascular symptoms: a systematic review and meta-analysis2016In: European Journal of Neurology, ISSN 1351-5101, E-ISSN 1468-1331, Vol. 23, no 7, p. 1241-1247Article in journal (Refereed)
    Abstract [en]

    Background and purpose: Many reports have shown an association between hypoechoic (echolucent) carotid atherosclerotic plaques and unstable features. In this meta-analysis our aim was to determine the role of carotid plaque echogenicity in predicting future cerebrovascular (CV) symptoms.

    Methods: Electronic databases (PubMed, MEDLINE, EMBASE and Cochrane Center Register) up to September 2015 were systematically searched. Studies with ultrasound-based characterization of carotid artery plaque echogenicity and its association with focal neurological symptoms of vascular origin were eligible for analysis. In the meta-analysis, heterogeneity was measured usingI2 statistics and publication bias was evaluated using the Begg–Mazumdar test. In addition several comparisons between subgroups were performed.

    Results: Of 1387 identified reports, eight studies with asymptomatic patients and three studies with symptomatic patients were meta-analyzed. Pooled analysis showed an association between echolucent carotid plaques and future CV events in asymptomatic patients [relative risk 2.72 (95% confidence interval 1.86–3.96)] and recurrent symptoms in symptomatic patients [relative risk 2.97 (95% confidence interval 1.85–4.78)]. The association was preserved for all stenosis degrees in asymptomatic patients, whilst patients with echolucent plaques and severe stenosis were at higher risk of future events. Also, computer-assisted methods for assessment of carotid plaque echogenicity and studies analyzing ultrasound data collected after the year 2000 showed better prediction.

    Conclusions: In asymptomatic and symptomatic patients, analysis of carotid plaque echogenicity could identify those at high risk of CV events.

  • 39.
    Jashari, Fisnik
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Ibrahimi, Pranvera
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Johansson, Elias
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine. Department of Clinical Sciences, Danderyds Hospital, Karolinska Institute, Stockholm, Sweden.
    Henein, Michael Y.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Carotid IM-GSM is better than IMT for identifying patients with multiple arterial disease2018In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, E-ISSN 1651-2006, Vol. 52, no 2, p. 93-99Article in journal (Refereed)
    Abstract [en]

    Objective. Atherosclerosis is a systemic inflammatory disease that can affect more than one arterial bed simultaneously. The aim of this study was to determine the relationship between ultrasound markers of atherosclerosis and multiple arterial disease. Design. We have included 87 currently asymptomatic carotid disease patients (mean age 69 +/- 6 year, 34% females) in this study. Intima media thickness (IMT) and intima media-grey scale median (IM-GSM) were measured in the common carotid artery (CCA), and correlated with previous and/or current atherosclerotic vascular disease in the coronary, carotid and lower extremities. Patients were divided into three groups: (1) asymptomatic, (2) previous symptoms in one arterial territory and (3) previous symptoms in multiple arterial territories. Results. Patients with previous disease in the coronary arteries had higher IMT (p=.034) and lower IM-GSM (p<.001), and those with prior stroke had lower IM-GSM (p=.007). Neither IMT nor IM-GSM was different between patients with and without previous lower extremity vascular disease. IM-GSM was significantly different between groups, it decreased significantly with increasing number of arterial territories affected (37.7 +/- 15.4 vs. 29.3 +/- 16.4 vs. 20.7 +/- 12.9) p<.001, for asymptomatic, symptoms in one and in multiple arterial systems, respectively. Conventional IMT was not significantly different between groups p=.49. Conclusion. Carotid IMT was higher and IM-GSM lower in patients with symptomatic nearby arterial territories but not in those with peripheral disease. In contrast to conventional IMT, IM-GSM can differentiate between numbers of arterial territories affected by atherosclerosis, suggesting that it is a better surrogate for monitoring multiple arterial territory disease.

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  • 40.
    Jashari, Fisnik
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Ibrahimi, Pranvera
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Johansson, Elias
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Henein, Michael Y.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Carotid im-gsm is related to multisite atherosclerosis disease2015In: Atherosclerosis, ISSN 0021-9150, E-ISSN 1879-1484, Vol. 241, no 1, p. E164-E164Article in journal (Other academic)
  • 41.
    Jiang, Biao
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Ali, Hazrat
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Imaging carotid wall mechanical heterogeneity in ultrasound image sequences using Eulerian video magnification2020In: Proceedings - IEEE 20th International Conference on Bioinformatics and Bioengineering, BIBE 2020, IEEE, 2020, p. 785-788, article id 9288064Conference paper (Refereed)
    Abstract [en]

    Atherosclerosis is a cardiovascular disease causing gradual infiltration of fatty streaks in the arterial wall and eventually plaque build-up that may rupture and cause a stroke. This induces changes in local biomechanics in response to systemic pressure variations. Such mechanical heterogeneities in the carotid arteries can be studied using ultrasound imaging methods. However, in 2-D ultrasound imaging, mechanical heterogeneity may result in both in-plane motions as well as out-of-plane motion, the latter causing intensity variations. Here, we evaluate linear Eulerian video magnification (EVM) processing on carotid ultrasound image sequences, and its ability to image local mechanical heterogeneity. In addition, we explore the method on several ultrasound image sequences from carotid wall tissues at different atherosclerotic disease stages ranging from healthy, early and late atherosclerosis, as well as changes with pharmacological treatment. The results show that linear EVM can be used to magnify motions in carotid ultrasound image sequences, and to derive heterogeneity maps that can visualize mechanical aspects of the carotid walls and its composition. Empirical case study on carotid walls indicate that the heterogeneity maps transition from homogenic to heterogenic pattern with progression of the atherosclerotic disease. The findings of this work show that mechanical heterogeneity imaging may be important in assessing atherosclerotic disease progression and potential risk prediction.

  • 42.
    Karlsson, J Stefan
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Roeleveld, Karin
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Holtermann, Andreas
    Östlund, Nils
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Signal processing of the surface electromyogram to gain insight into neuromuscular physiology.2009In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 367, no 1887, p. 337-356Article in journal (Refereed)
    Abstract [en]

    A surface electromyogram (sEMG) contains information about physiological and morphological characteristics of the active muscle and its neural strategies. Because the electrodes are situated on the skin above the muscle, the sEMG is an easily obtainable source of information. However, different combinations of physiological and morphological characteristics can lead to similar sEMG signals and sEMG recordings contain noise and other artefacts. Therefore, many sEMG signal processing methods have been developed and applied to allow insight into neuromuscular physiology. This paper gives an overview of important advances in the development and applications of sEMG signal processing methods, including spectral estimation, higher order statistics and spatio-temporal processing. These methods provide information about muscle activation dynamics and muscle fatigue, as well as characteristics and control of single motor units (conduction velocity, firing rate, amplitude distribution and synchronization).

  • 43. Khangure, Simon R.
    et al.
    Benhabib, Hadas
    Machnowska, Matylda
    Fox, Allan J.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Herod, Wendy
    Maggisano, Robert
    Sjöberg, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Medicine. Department of Clinical Sciences, Karolinska Institutet Danderyds Hospital, Stockholm, Sweden.
    Hojjat, Seyed-Parsa
    Hopyan, Julia
    Aviv, Richard I.
    Johansson, Elias
    Carotid near-occlusion frequently has high peak systolic velocity on Doppler ultrasound2018In: Neuroradiology, ISSN 0028-3940, E-ISSN 1432-1920, Vol. 60, no 1, p. 17-25Article in journal (Refereed)
    Abstract [en]

    Purpose: Carotid near-occlusion is a tight atherosclerotic stenosis of the internal carotid artery (ICA) resulting in decrease in diameter of the vessel lumen distal to the stenosis. Near-occlusions can be classified as with or without full collapse, and may have high peak systolic velocity (PSV) across the stenosis, mimicking conventional > 50% carotid artery stenosis. We aimed to determine how frequently near-occlusions have high PSV in the stenosis and determine how accurately carotid Doppler ultrasound can distinguish high-velocity near-occlusion from conventional stenosis.

    Methods: Included patients had near-occlusion or conventional stenosis with carotid ultrasound and CT angiogram (CTA) performed within 30 days of each other. CTA examinations were analyzed by two blinded expert readers. Velocities in the internal and common carotid arteries were recorded. Mean velocity, pulsatility index, and ratios were calculated, giving 12 Doppler parameters for analysis.

    Results: Of 136 patients, 82 had conventional stenosis and 54 had near-occlusion on CTA. Of near-occlusions, 40 (74%) had high PSV (≥ 125 cm/s) across the stenosis. Ten Doppler parameters significantly differed between conventional stenosis and high-velocity near-occlusion groups. However, no parameter was highly sensitive and specific to separate the groups.

    Conclusion: Near-occlusions frequently have high PSV across the stenosis, particularly those without full collapse. Carotid Doppler ultrasound does not seem able to distinguish conventional stenosis from high-velocity near-occlusion. These findings question the use of ultrasound alone for preoperative imaging evaluation.

  • 44. Lindberg, F
    et al.
    Öhberg, Fredrik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Brodin, LA
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Assessment of intramuscular activation patterns using ultrasound M-mode strain2013In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 23, no 4, p. 879-885Article in journal (Refereed)
    Abstract [en]

    The intramuscular activation pattern can be connected to the motor unit recruitment strategy of force generation and fatigue resistance. Electromyography has earlier been used in several studies to quantify the spatial inhomogeneity of the muscle activation. We applied ultrasound M-mode strain to study the activation pattern through the tissue deformation. Correlation values of the strain at different force levels were used to quantify the spatial changes in the activation. The assessment was done including the biceps brachii muscle of 8 healthy subjects performing isometric elbow flexion contractions ranging from 0% to 80% of maximum voluntary contraction. The obtained results were repeatable and demonstrated consistent changes of the correlation values during force regulation, in agreement with previously presented EMG-results. Both intra-subject and inter-subject activation patterns of strain were considered along and transverse the fiber direction. The results suggest that ultrasound M-mode strain can be used as a complementary method to study intramuscular activation patterns with high spatial resolution.

    (C) 2013 Elsevier Ltd. All rights reserved.

  • 45. Lindberg, Frida
    et al.
    Mårtensson, Mattias
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Brodin, Lars-Åke
    Evaluation of ultrasound Tissue Velocity Imaging: a phantom study of velocity estimation in skeletal muscle low-level contractions2013In: BMC Medical Imaging, E-ISSN 1471-2342, Vol. 13, no 16Article in journal (Refereed)
    Abstract [en]

    Background: Tissue Velocity Imaging (TVI) is an ultrasound based technique used for quantitative analysis of the cardiac function and has earlier been evaluated according to myocardial velocities. Recent years several studies have reported applying TVI in the analysis of skeletal muscles. Skeletal tissue velocities can be very low. In particular, when performing isometric contractions or contractions of low force level the velocities may be much lower compared to the myocardial tissue velocities. Methods: In this study TVI was evaluated for estimation of tissue velocities below the typical myocardial velocities. An in-house phantom was used to see how different PRF-settings affected the accuracy of the velocity estimations. Results: With phantom peak velocity at 0.03 cm/s the error ranged from 31% up to 313% with the different PRF-settings in this study. For the peak velocities at 0.17 cm/s and 0.26 cm/s there was no difference in error with tested PFR settings, it is kept approximately around 20%. Conclusions: The results from the present study showed that the PRF setting did not seem to affect the accuracy of the velocity estimation at tissue velocities above 0.17 cm/s. However at lower velocities (0.03 cm/s) the setting was crucial for the accuracy. The PRF should therefore preferable be reduced when the method is applied in low-level muscle contraction.

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  • 46. Lindberg, Frida
    et al.
    Öhberg, Fredrik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Granåsen, Gabriel
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Brodin, Lars-Åke
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Pennation angle dependency in skeletal muscle tissue doppler strain in dynamic contractions2011In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 37, no 7, p. 1151-1160Article in journal (Refereed)
    Abstract [en]

    Tissue velocity imaging (TVI) is a Doppler based ultrasound technique that can be used to study regional deformation in skeletal muscle tissue. The aim of this study was to develop a biomechanical model to describe the TVI strain's dependency on the pennation angle. We demonstrate its impact as the subsequent strain measurement error using dynamic elbow contractions from the medial and the lateral part of biceps brachii at two different loadings; 5% and 25% of maximum voluntary contraction (MVC). The estimated pennation angles were on average about 4° in extended position and increased to a maximal of 13° in flexed elbow position. The corresponding relative angular error spread from around 7% up to around 40%. To accurately apply TVI on skeletal muscles, the error due to angle changes should be compensated for. As a suggestion, this could be done according to the presented model.

  • 47.
    Lindkvist, Markus
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Granåsen, Gabriel
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Coherent Derivation of Equations for Differential Spectroscopy and Spatially Resolved Spectroscopy: An undergraduate tutorial2013In: Spectroscopy Letters, ISSN 0038-7010, E-ISSN 1532-2289, Vol. 46, no 4, p. 243-249Article in journal (Refereed)
    Abstract [en]

    Near-infrared spectroscopy (NIRS) is a spectroscopic method that is frequently used in health care and sports medicine to monitor oxygenation parameters in biological tissue. This tutorial provides a coherent derivation of equations for differential spectroscopy and spatially resolved spectroscopy, from basic theories to implementable equations. The basic theories are applicable to any kind of tissue oximeter but mainly focus on continuous-wave instruments. 

  • 48.
    Lindkvist, Markus
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Granåsen, Gabriel
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Department of Epidemiology and Global Health.
    Precontractile optical response during excitation-contraction in human muscle revealed by non-invasive high-speed spatiotemporal NIR measurement2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, article id 213Article in journal (Refereed)
    Abstract [en]

    During muscle contraction the excitation-contraction process mediates the neural input and mechanical output. Proper muscle function and body locomotion depends on the status of the elements in the same process. However, non-invasive and in-vivo methods to study this are not available. Here we show the existence of an optical response occurring during the excitation-contraction process in human biceps brachii muscle. We developed a non-invasive instrument from a photodiode array and light emitting diodes to detect spatially propagating (similar to 5 m/s) and precontractile (similar to 6 ms onset) optical signals closely related to the action potential during electrostimulation. Although this phenomenon was observed 60 years ago on isolated frog muscle cells in the lab, it has not been shown in-vivo before now. We anticipate our results to be a starting point for a new category in-vivo studies, characterising alterations in the excitation-contraction process in patients with neuromuscular disease and to monitor effects of therapy.

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  • 49.
    Lindkvist, Markus
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Absolute quantifications of oxy- and deoxyhemoglobin concentrations by combination of differentially resolved spectroscopy and spatially resolved spectroscopy2015In: Spectroscopy Letters, ISSN 0038-7010, E-ISSN 1532-2289, Vol. 48, no 3, p. 170-172Article in journal (Refereed)
    Abstract [en]

    This letter proposes a theoretical framework to calculate absolute concentrations of oxy- and deoxyhemoglobin using continuous-wave near-infrared spectroscopy. While previous methods on this topic require assumptions on constant blood volume, the proposed method does not. Equations for the absolute concentrations were derived from a combination of the modified Beer-Lambert equation and the theory of diffusion of photons in turbid media. The method has an advantage over and is theoretically consistent with previous methods. It needs yet to be evaluated in an experimental study.

  • 50. Lindqvist, G
    et al.
    Grönlund, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Söderberg, Stefan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Gonzalez, Manuel
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Henein, Michael Y
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Tossavainen, Erik
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
    Biventricular dysfunction and their consequences predict mortality in pulmonary arterial hypertension2014In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 35, no Supplement 1, Meeting abstract P492, p. 78-78Article in journal (Other academic)
12 1 - 50 of 83
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