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  • 1.
    Höglund, Gustav
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grip, Helena
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Öhberg, Fredrik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    The importance of inertial measurement unit placement in assessing upper limb motion2021In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 92, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Motion analysis using inertial measurement units (IMU) has emerged as an alternative to optical motion capture. However, the validity and reliability of upper limb measurements varies significantly between studies. The objective of this study was to determine how sensor placement affects kinematic output in the assessment of motion of the arm, shoulder, and scapula. IMUs were placed proximally/distally on arms, and medially/laterally on the scapula, in a group of eleven healthy participants, while performing nine different motion tasks. Linear regressions and mixed models analysed how these different sensor placements affected the estimated joint motion by establishing the linear relationship between sensors placed on the same body segment. The placement of sensors affected the measured kinematic output considerably, most prominent affect was seen for sensor placement on scapula during flexion and abduction, and on forearm during pronation/supination. The slope of the linear regression lines was 2.5 during flexion, 2.7 during abduction, and 1.8 for forearm pronation/supination. The results of this study suggest that the forearm sensor should be placed on the dorsal side of the forearm, at the distal end; the upper arm sensor should be placed laterally, on the distal part of the arm; and the sensor on the scapula should be placed cranially, along the spine of scapula.

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  • 2.
    Kulmala, Katariina
    et al.
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Karjalainen, Hannu
    Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
    Kokkonen, Harri
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Tiitu, Virpi
    Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
    Kovanen, Vuokko
    Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland.
    Lammi, Mikko
    Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
    Jurvelin, Jukka
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Korhonen, Rami
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Töyräs, Juha
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland.
    Diffusion of ionic and non-ionic contrast agents in articular cartilage with increased cross-linking: contribution of steric and electrostatic effects2013In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 35, no 10, p. 1415-20Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To investigate the effect of threose-induced collagen cross-linking on diffusion of ionic and non-ionic contrast agents in articular cartilage.

    DESIGN: Osteochondral plugs (Ø=6mm) were prepared from bovine patellae and divided into two groups according to the contrast agent to be used in contrast enhanced computed tomography (CECT) imaging: (I) anionic ioxaglate and (II) non-ionic iodixanol. The groups I and II contained 7 and 6 sample pairs, respectively. One of the paired samples served as a reference while the other was treated with threose to induce collagen cross-linking. The equilibrium partitioning of the contrast agents was imaged after 24h of immersion. Fixed charge density (FCD), water content, contents of proteoglycans, total collagen, hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP) and pentosidine (Pent) cross-links were determined as a reference.

    RESULTS: The equilibrium partitioning of ioxaglate (group I) was significantly (p=0.018) lower (-23.4%) in threose-treated than control samples while the equilibrium partitioning of iodixanol (group II) was unaffected by the threose-treatment. FCD in the middle and deep zones of the cartilage (p<0.05) and contents of Pent and LP (p=0.001) increased significantly due to the treatment. However, the proteoglycan concentration was not systematically altered after the treatment. Water content was significantly (-3.5%, p=0.007) lower after the treatment.

    CONCLUSIONS: Since non-ionic iodixanol showed no changes in partition after cross-linking, in contrast to anionic ioxaglate, we conclude that the cross-linking induced changes in charge distribution have greater effect on diffusion compared to the cross-linking induced changes in steric hindrance.

  • 3.
    Panarese, Alessandro
    et al.
    Scuola Superiore Sant’Anna, Pisa.
    Edin, Benoni B
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    A modified low-cost haptic interface as a tool for complex tactile stimulation2011In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 33, no 3, p. 386-390Article in journal (Refereed)
    Abstract [en]

    This study describes the development and evaluation of a platform for the investigation of the human tactile ability. Specifically, it enables precise and reproducible application of time-varying 3D force stimuli to the skin of an immobilized human limb. We proceeded in the following steps: (1) programming a low-cost haptic interface to apply time-varying 3D force stimuli to a fixed rigid target, (2) implementing a combined feed-forward/feedback controller to improve the platform's precision and reliability in force stimulation, (3) determining the optimal tuning of the control loop parameters and (4) evaluating the system's performances when applying time-varying 3D force stimuli to an immobilized human finger pad. The system's performances were evaluated in terms of the accuracy and repeatability when delivering standard 3D force stimuli, i.e., stimuli with specified force components in the normal and skin tangential directions. Within the range of forces tested (5N in various directions), the maximum difference between the actual force and the desired value during static phases was <30mN (accuracy) and the root-mean-square of the standard deviation (repeatability) was 15mN during static phases and <75mN during dynamic phases.

  • 4.
    Sierpowska, Joanna
    et al.
    Department of Physics, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Institute of Biomedicine, Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Hakulinen, Mikko
    Department of Physics, University of Kuopio, Kuopio, Finland.
    Jurvelin, Jukka
    Department of Physics, University of Kuopio, Kuopio, Finland; Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Kuopio, Finland.
    Lappalainen, Reijo
    Department of Physics, University of Kuopio, Kuopio, Finland.
    Töyräs, Juha
    Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Kuopio, Finland.
    Effect of human trabecular bone composition on its electrical properties.2007In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 29, no 8, p. 845-852, article id 17097909Article in journal (Refereed)
    Abstract [en]

    Mechanical properties of bone are determined not only by bone mineral density (BMD), but also by tissue trabecular structure and organic composition. Impedance spectroscopy has shown potential to diagnose trabecular bone BMD and strength, however, the relationships between organic composition and electrical and dielectric properties have not been systematically investigated. To investigate these issues organic composition of 26 human trabecular bone samples harvested from the distal femur and proximal tibia was determined and compared with relative permittivity, loss factor, conductivity, phase angle, specific impedance and dissipation factor measured at wide range (50 Hz to 5 MHz) of frequencies. A strong linear correlation was found between the relative permittivity at 1.2 MHz and trabecular bone fat content (r = -0.85, p<0.01, n=26). On the other hand, relative permittivity measured at 200 Hz served as a good predictor of water content (r = 0.83). Phase angle, specific impedance and especially conductivity were strongly related to the trabecular bone dry density and water content (|r| > or = 0.69). Variation in bone tissue collagen content was strongly related to the relative permittivity measured at 1.2 MHz (r = 0.64), but only moderately to other parameters. Glycosaminoglycan content showed no significant relations with any investigated electrical parameters. The present study indicates that if the trabecular bone composition is known, the relationships presented in this study could facilitate calculation of current field distribution, e.g. during electrical stimulation of osteogenesis. On the other hand, our results suggest that permittivity measured at low (<1 kHz) or high (>100 kHz) frequencies could be used, e.g. during implant surgery, for prediction of trabecular bone water or fat contents, respectively.

  • 5.
    Öhberg, Fredrik
    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.
    Vänn, Mårten
    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.
    Jonzén, Karolina
    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.
    Edström, Urban
    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.
    Sundström, Nina
    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).
    Comparison between two mobile applications measuring shoulder elevation angle–A validity and feasibility study2021In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 98, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Pain in the shoulder complex affects the working population where work with elevated arms is a risk factor. The aim of the present study was to compare a mobile application for measurements of arm elevation, ErgoExposure, against an existing mobile application, ErgoArmMeter, in a laboratory setting and to test the feasibility in a field trial. Eleven persons performed three tasks in the laboratory setting: static, dynamic, and simulated work tasks, where the applications were validated against an optical tracking system (OTS). Also, ErgoExposure was tested by a teacher in a real-world situation. Limits of agreement for the static task varied between -6.1° to 4.2° (ErgoExposure) and between -7.6° to 5.2° (ErgoArmMeter). The average root mean square difference for dynamic and simulated work tasks was 3.4° (ErgoExposure) and 7.7° (ErgoArmMeter). From the field trial, different work tasks produced distinct exposure variation analysis patterns. Both apps showed similar results compared to OTS, but ErgoExposure was more accurate than ErgoArmMeter.

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