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  • 1.
    Andersson, Nina
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology. Neurologi.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Assessment of cerebrospinal fluid outflow conductance using constant-pressure infusion - a method with real time estimation of reliability2005In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 26, no 6, p. 1137-1148Article in journal (Refereed)
  • 2.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Department of Clinical Sciences.
    Wearable systems and sensors for the assessment of motor control: Development and validation of methods for clinical assessment of idiopathic normal pressure hydrocephalus2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Human gait and balance are controlled by automatic processes in the central nervous system, and in sensory and proprioceptive systems. If a disturbance occurs in any of these complex structures, it may lead to balance and gait problems. Equally important are the systems controlling the upper extremity functions where reach, grasp and manipulation skills may be affected. For the neurodegenerative disease idiopathic normal pressure hydrocephalus (iNPH), balance and gait disturbances are cardinal symptoms. Motor control of the upper extremities is also affected. In clinic today, physical impairment of persons with iNPH is commonly visually assessed using subjective, course tests with ordinal scales with the risk of missing minor changes. There is a lack of objective and quantitative ways to measure motor control in daily patient care. The aim of this thesis was to develop and validate tools for objective assessment of parameters that affect motor control in persons with iNPH.

    Postural stability in stance and walking was assessed using gyroscopes in patients with iNPH, healthy elderly (HE) and patients with ventriculomegaly (VM). Compared to HE, patients with iNPH had reduced postural stability and relied less on vision. iNPH patients also had a lower trunk sway velocity than VM during walking. The gyroscopic system could quantitatively assess postural deficits in iNPH, making it a potentially useful tool for diagnosis and for clinical follow-up. The differences found during gait also suggests that walking, rather than quiet stance, should be further investigated for facilitating differential diagnosis compared to other patient groups with ventriculomegaly.

    The gait in patients with iNPH is according to guidelines defined as slow, shuffling with a low foot-lift, and wide based. To objectively quantify the latter two features, a system (Striton) was developed in-house to assess the increased distance between the feet and the peak heel-height at the push-off phase of the gait cycle. It was validated in experimental setups, compared to gold standard motion capture systems (MCS), on healthy elderly (HE), through test-retest and day-to-day evaluations, and in four patients with iNPH. Striton demonstrated high correlations, in step-width and in heel-height, compared with the MCS. The mean step-width in the HE was 5.2 ± 0.9 cm (mean±Standard Deviation) and the heel-height 16.7±0.6 cm. Test-retest and day-to-day variations were small, ±0.5 cm in step-width and ±1.2 cm in heel-height, and differences in the parameters were seen between HE and iNPH both before and after surgery. Thus, Striton has the potential of quantitatively assessing gait parameters in HE and iNPH in a valuable manner.

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  • 3.
    Bäcklund, Tomas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Frankel, Jennifer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Israelsson, Hanna
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience. Vrinnevi Hospital, Norrköping, Sweden.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Sundström, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Trunk sway in idiopathic normal pressure hydrocephalus: quantitative assessment in clinical practice2017In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, p. 62-70, article id 54Article in journal (Refereed)
    Abstract [en]

    Background: In diagnosis and treatment of patients with idiopathic normal pressure hydrocephalus (iNPH), there is need for clinically applicable, quantitative assessment of balance and gait. Using a body worn gyroscopic system, the aim of this study was to assess postural stability of iNPH patients in standing, walking and during sensory deprivation before and after cerebrospinal fluid (CSF) drainage and surgery. A comparison was performed between healthy elderly (HE) and patients with various types of hydrocephalus (ventriculomegaly (VM)).

    Methods: Trunk sway was measured in 31 iNPH patients, 22 VM patients and 58 HE. Measurements were performed at baseline in all subjects, after CSF drainage in both patient groups and after shunt surgery in the iNPH group.

    Results: Preoperatively, the iNPH patients had significantly higher trunk sway compared to HE, specifically for the standing tasks (p < 0.001). Compared to VM, iNPH patients had significantly lower sway velocity during gait in three of four cases on firm support (p < 0.05). Sway velocity improved after CSF drainage and in forward-backward direction after surgery (p < 0.01). Compared to HE both patient groups demonstrated less reliance on visual input to maintain stable posture.

    Conclusions: INPH patients had reduced postural stability compared to HE, particularly during standing, and for differentiation between iNPH and VM patients sway velocity during gait is a promising parameter. A reversible reduction of visual incorporation during standing was also seen. Thus, the gyroscopic system quantitatively assessed postural deficits in iNPH, making it a potentially useful tool for aiding in future diagnoses, choices of treatment and clinical follow-up. 

  • 4.
    Bäcklund, Tomas
    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.
    Sundström, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Single sensor measurement of heel-height during the push-off phase of gait2021In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 42, no 10, article id 105016Article in journal (Refereed)
    Abstract [en]

    Objective: In healthy gait a forceful push-off is needed to get an efficient leg swing and propulsion, and a high heel lift makes a forceful push-off possible. The power of the push-off is decreased with increased age and in persons with impaired balance and gait. The aim of this study was to evaluate whether a wearable equipment (Striton) and algorithms to estimate vertical heel-height during gait from a single optical distance sensor is reliable and feasible for clinical applications.

    Approach: To assess heel-height with the Striton system an optical distance sensor was used to measure the distance to the floor along the shank. An algorithm was created to transform this measure to a vertical distance. The heel-height was validated in an experimental setup, against a 3D motion capture system (MCS), and test-retest and day-to-day tests were performed on 10 elderly persons. As a reference material 83 elderly persons were included, and heel-height was measured before and after surgery in four patients with the neurological disorder idiopathic normal pressure hydrocephalus (iNPH).

    Main results: In the experimental setup the accuracy was high with a maximum error of 2% at all distances, target colours and inclination angles, and the correlation to the MCS was R = 0.94. Test-retest and day-to-day tests were equal within ±1.2 cm. Mean heel-height of the elderly persons was 16.5 ± 0.6 cm and in the patients with iNPH heel-height was increased from 11.2 cm at baseline to 15.3 cm after surgery.

    Significance: Striton can reliably measure heel-height during gait, with low test-retest and day-to-day variability. The system was easy to attach, and simple to use, which makes it suitable for clinical applications.

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  • 5.
    Bäcklund, Tomas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Öhberg, Fredrik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grip, Helena
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Johansson, Gudrun
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation.
    Sundström, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    O 035 - A novel method to measure step width during the swing phase of gait2018In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 65, p. 71-72Article in journal (Refereed)
  • 6.
    Bäcklund, Tomas
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Öhberg, Fredrik
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Johansson, Gudrun
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation.
    Grip, Helena
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Sundström, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Novel, clinically applicable method to measure step-width during the swing phase of gait2020In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 41, no 6, article id 065005Article in journal (Refereed)
    Abstract [en]

    Objective: Step-width during walking is an indicator of stability and balance in patients with neurological disorders, and development of objective tools to measure this clinically would be a great advantage. The aim of this study was to validate an in-house-developed gait analysis system (Striton), based on optical and inertial sensors and a novel method for stride detection, for measuring step-width during the swing phase of gait and temporal parameters.

    Approach: The step-width and stride-time measurements were validated in an experimental setup, against a 3D motion capture system and on an instrumented walkway. Further, test-retest and day-to-day variability were evaluated, and gait parameters were collected from 87 elderly persons (EP) and four individuals with idiopathic normal pressure hydrocephalus (iNPH) before/after surgery.

    Main results: Accuracy of the step-width measurement was high: in the experimental setup mean error was 0.08 +/- 0.25 cm (R = 1.00) and against the 3D motion capture system 0.04 +/- 1.12 cm (R = 0.98). Test-retest and day-to-day measurements were equal within +/- 0.5 cm. Mean difference in stride time was -0.003 +/- 0.008 s between Striton and the instrumented walkway. The Striton system was successfully applied in the clinical setting on individuals with iNPH, which had larger step-width (6.88 cm, n = 4) compared to EP (5.22 cm, n = 87).

    Significance: We conclude that Striton is a valid, reliable and wearable system for quantitative assessment of step-width and temporal parameters during gait. Initial measurements indicate that the newly defined step-width parameter differs between EP and patients with iNPH and before/after surgery. Thus, there is potential for clinical applicability in patients with reduced gait stability.

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  • 7.
    Eklund, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Henein, Michael Y
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology. Heart centrum, Umeå universitet.
    Natural angioplasty as a mechanical effect of exercise2013In: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 168, no 3, p. 3083-3085Article in journal (Refereed)
  • 8.
    Eklund, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Andersson, Britt M
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindahl, Olof A
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Evaluation of applanation resonator sensors for intra-ocular pressure measurement: results from clinical and in vitro studies.2003In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 41, no 2, p. 190-197Article in journal (Refereed)
    Abstract [en]

    Glaucoma is an eye disease that, in its most common form, is characterised by high intra-ocular pressure (IOP), reduced visual field and optic nerve damage. For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring IOP. Recently, an applanation resonator sensor (ARS) for measuring IOP was introduced and evaluated using an in vitro pig-eye model. In the present study, the first clinical evaluation of the same probe has been carried out, with experiments in vivo on human eyes. There was a low but significant correlation between IOP(ARS) and the IOP measured with a Goldmann applanation tonometer (r = 0.40, p = 0.001, n = 72). However, off-centre positioning of the sensor against the cornea caused a non-negligible source of error. The sensor probe was redesigned to have a spherical, instead of flat, contact surface against the eye and was evaluated in the in vitro model. The new probe showed reduced sensitivity to off-centre positioning, with a decrease in relative deviation from 89% to 11% (1 mm radius). For normalised data, linear regression between IOP(ARS) and direct IOP measurement in the vitreous chamber showed a correlation of r = 0.97 (p < 0.001, n = 108) and a standard deviation for the residuals of SD < or = 2.18 mm Hg (n = 108). It was concluded that a spherical contact surface should be preferred and that further development towards a clinical instrument should focus on probe design and signal analysis.

  • 9.
    Fröjse, Rolf
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
    Arnerlöv, Conny
    Hedberg, Bengt
    Häggström, Mats
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindahl, Olof
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Ängquist, Karl-Axel
    A new method for continuous tonometric pCO2 measurement - in vitro studies.1999In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 20, no 2, p. 129-136Article in journal (Refereed)
    Abstract [en]

    The available methods for tonometric pCO2 measurement only provide the possibility of performing intermittent registrations. A new method allowing continuous tonometric pCO2 measurement has been developed and tested in an in vitro model. A standard tonometer for intestinal pCO2 measurement was modified to allow continuous perfusion of the balloon with physiological saline solution in a closed system. The pCO2 in the system was determined in a specially constructed measurement chamber with a TCM20 percutaneous pCO2 monitor. In this in vitro model the tonometer balloon was placed in a saline bath with a constant pCO2 concentration and the measurements from the closed circulating system were compared with those obtained from a standard tonometer placed in the same bath. In 8 and 24 h experiments the circulating system measured the pCO2 value as accurately and reliably as traditional tonometry. This study indicates that the new method makes continuous monitoring of pCO2 possible.

  • 10.
    Fröjse, Rolf
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
    Hedberg, Bengt
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindahl, Olof
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Häggström, Mats
    Ängquist, Karl-Axel
    Arnerlöv, Conny
    Intestinal pHi studied with continuous saline tonometry during ischaemia and reperfusion in the pig.2002In: European Journal of Vascular and Endovascular Surgery, ISSN 1078-5884, E-ISSN 1532-2165, Vol. 24, no 2, p. 150-155Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To evaluate continuous saline tonometry for detection of progressive intestinal ischaemia and reperfusion in a porcine model. DESIGN: In eight anaesthetised pigs, small bowel mucosal pCO2 was recorded by means of two identical equipments for continuous saline tonometry and a standard tonometry balloon during ischaemia and reperfusion. RESULTS: Both systems of saline tonometry functioned stably during the four hour protocol ischaemia, although not significant until after 45 min for one of the tonometers. CONCLUSION: The equipment for continuous saline tonometry has a good reactivity, an accuracy comparable with standard tonometry.

  • 11.
    Fröjse, Rolf
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
    Hedberg, Bengt
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindahl, Olof
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Häggström, Mats
    Ängquist, Karl-Axel
    Arnerlöv, Conny
    Validation of a novel method for continuous saline tonometry in a procine model.2001In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 22, no 3, p. 453-460Article in journal (Refereed)
    Abstract [en]

    Only intermittent and semi-continuous tonometric measurement of gastric and intestinal pHi is possible with the equipment available today. Earlier we developed a system for continuous saline tonometry and tested it in vitro. To assess the in vivo reliability of this method for continuous gastrointestinal saline tonometry, a standard tonometer for measurement of intestinal pCO2 and corresponding pHi was modified to allow continuous perfusion of physiological saline in a closed system and tested in a porcine model. In 11 anaesthetized and haemodynamically stable pigs, two continuous tonometry balloons were inserted into the distal small bowel, and a standard tonometry balloon was used as reference. To test long-term function of the continuous tonometers the research protocol lasted for eight hours. The two continuous saline tonometers performed well, and after an equilibration time of three hours the mean pHi values were stable between 7.35 and 7.43 and between 7.32 and 7.39 respectively. The standard tonometer measured stable pHi values. These preliminary studies indicate that continuous saline tonometry performs well over eight hours with a small bias and a good precision.

  • 12. Hallberg, Per
    et al.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Clinical evaluation of applanation resonance tonometry: a comparison with Goldmann applanation tonometry.2007In: Journal of glaucoma, ISSN 1057-0829, E-ISSN 1536-481X, Vol. 16, no 1, p. 88-93Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose of this study was to calibrate and evaluate the precision of the new applanation resonance tonometry (ART) in a clinical study designed in accordance with the International Standard Organization's requirements. METHODS: This was a prospective, randomized, single-center study, where healthy volunteers and patients participated. A total of 153 eyes were divided into 3 groups with respect to their intraocular pressure (IOP) at screening: <16 mm Hg, 16 to 23 mm Hg, and >23 mm Hg. IOP was measured with Goldmann applanation tonometry (GAT) as reference method and by ART in both a biomicroscope (ARTBiom) and a handheld (ARTHand) setup with a 10-minutes pause between methods. The mean of 6 readings was regarded as one measurement value. RESULTS: Mean age of the subjects was 59 years (range 20 to 87 y). GAT showed a mean IOP of 20.0 mm Hg (range 8.5 to 43.5 mm Hg, n=153). The precision was 2.07 mm Hg for ARTBiom and 2.50 mm Hg for ARTHand, with a significant dependency for age as compared with GAT. Measurement order produced a decreasing IOP with a mean of 2.3 mm Hg between the first and last method. CONCLUSIONS: The precision obtained in both ARTBiom and ARTHand was within the limits set by the International Standard Organization standards for tonometers. The standardized procedure and the stability of the biomicroscope setup resulted in a slightly better precision as compared with the handheld setup. Despite a 10-minutes pause between measurements, the order was a significant factor, possibly because the patients were more apprehensive at the first measurement.

  • 13.
    Hallberg, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Bäcklund, Tomas
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Symmetric sensor for applanation resonance tonometry of the eye2006In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 1-2, p. 54-60Article in journal (Refereed)
    Abstract [en]

    Applanation resonance tonometry (ART) has been shown in a number of studies to be useful for measuring intraocular pressure (IOP). Data from in vitro laboratory bench testing, where the sensor was carefully centralised onto the cornea, has been very consistent with good precision in the determination of IOP. However, in a clinical study the unavoidable off-centre placement of the sensor against the cornea resulted in a reduced precision. The aim of this study was to evaluate a new design of the sensor with a symmetric sensor probe and a contact piece with a larger diameter. Two in vitro porcine eye experimental set-ups were used. One bench-based for examining position dependence and one biomicroscope-based set-up, simulating a clinical setting, for evaluating IOP(ART) precision at seven different pressure levels (1040 mmHg), set by connecting a saline column to the vitreous chamber. The reference IOP was recorded using a pressure transducer. There was no significant difference between four positions 1 mm off centre and the one centre position. The precision of the ART as compared with the reference pressure was +/- 1.03 mmHg (SD, n = 42). The design improvement has enhanced the precision of the ART in the biomicroscope set-up to be in parity with bench test results from a set-up using perfect positioning. This indicates that off-centre positioning was no longer a major contributor to the deviations in measured IOP. The precision was well within the limits set by ISO standard for eye tonometers. Therefore, a larger in vivo study on human eyes with the ART should be performed.

  • 14.
    Hallberg, Per
    et al.
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Lindén, Christina
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
    Lindahl, Olof A.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Bäcklund, Tomas
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Eklund, Anders
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Applanation resonance tonometry for intraocular pressure in humans2004In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 25, no 4, p. 1053-1065Article in journal (Refereed)
    Abstract [en]

    Glaucoma is a group of diseases associated with optic nerve damage and loss of visual field. The aetiology is not completely understood, but one of the major risk factors is elevated intraocular pressure (IOP). Reliable methods for measuring the IOP are therefore important. The aim of the study was to investigate the ability of the applanation resonance tonometry (ART) system, based on continuous force and area recording, to measure IOP in humans. Both the phase of initial indentation (IOPIndentation) and the phase when the sensor was removed (IOPRemoval) from the cornea were analysed. The Goldmann applanation tonometry (GAT) was used as reference method. The study included 24 healthy volunteers with normal IOP and 24 patients with elevated IOP. The correlation and standard deviation (SD) between IOPIndentation and IOPGAT was R = 0.92 (p < 0.001), SD = 3.6 mmHg, n = 104, and between IOPRemoval and IOPGAT R = 0.94 (p < 0.001), SD = 3.1 mmHg, n = 104. In conclusion, resonance sensor technology has made it possible to introduce a new multi-point method for measuring IOP, and the method is relevant for measuring IOP in humans. The study indicates that with further development towards elimination of position dependence, the ART has the potential to become a useful clinical instrument for IOP measurement.

  • 15.
    Hellström, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation. University Hospital of Northern Sweden, Umeå, Sweden.
    Lindahl, Olof
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation. University Hospital of Northern Sweden, Umeå, Sweden.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation. University Hospital of Northern Sweden, Umeå, Sweden.
    Karlsson, Marcus
    Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation. University Hospital of Northern Sweden, Umeå, Sweden.
    Hohnloser, Peter
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation. University Hospital of Northern Sweden, Umeå, Sweden.
    Bråndal, Anna
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine. University Hospital of Northern Sweden, Umeå, Sweden.
    Hu, Xiaolei
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation. University Hospital of Northern Sweden, Umeå, Sweden; Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, Sweden.
    Wester, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine. University Hospital of Northern Sweden, Umeå, Sweden.
    An intelligent rollator for mobility impaired persons, especially stroke patients2016In: Journal of Medical Engineering & Technology, ISSN 0309-1902, E-ISSN 1464-522X, Vol. 40, no 5, p. 270-279Article in journal (Refereed)
    Abstract [en]

    An intelligent rollator (IRO) was developed that aims at obstacle detection and guidance to avoid collisions and accidental falls. The IRO is a retrofit four-wheeled rollator with an embedded computer, two solenoid brakes, rotation sensors on the wheels and IR-distance sensors. The value reported by each distance sensor was compared in the computer to a nominal distance. Deviations indicated a present obstacle and caused activation of one of the brakes in order to influence the direction of motion to avoid the obstacle. The IRO was tested by seven healthy subjects with simulated restricted and blurred sight and five stroke subjects on a standardised indoor track with obstacles. All tested subjects walked faster with intelligence deactivated. Three out of five stroke patients experienced more detected obstacles with intelligence activated. This suggests enhanced safety during walking with IRO. Further studies are required to explore the full value of the IRO.

  • 16.
    Lindahl, Olof A
    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.
    Bäcklund, Tomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Ramser, Kerstin
    Department of Engineering Sciences and Mathematics, Lulea University of Technology, Lulea, Sweden.
    Liv, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Sustainable Health.
    Ljungberg, Börje
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Urology and Andrology.
    Bergh, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    A tactile resonance sensor for prostate cancer detection - Evaluation on human prostate tissue2021In: Biomedical Engineering & Physics Express, E-ISSN 2057-1976, Vol. 7, no 2, article id 025017Article in journal (Refereed)
    Abstract [en]

    Prostate cancer surgery risks erectile problems and incontinence for the patient. An instrument for guiding surgeons to avoid nerve bundle damage and ensure complete cancer removal is desirable. We present a tactile resonance sensor made of PZT ceramics, mounted in a 3D motorized translation stage for scanning and measuring tissue stiffness for detecting cancer in human prostate. The sensor may be used during surgery for guidance, scanning the prostate surface for the presence of cancer, indicating migration of cancer cells into surrounding tissue. Ten fresh prostates, obtained from patients undergoing prostate cancer surgery, were cut into 0.5 cm thick slices. Each slice was measured for tissue stiffness at about 25 different sites and compared to histology for validation cancer prediction by stiffness. The statistical analysis was based on a total of 148 sites with non-cancer and 40 sites with cancer. Using a generalized linear mixed model (GLMM), the stiffness data predicted cancer with an area under the curve of 0.74, after correcting for overfitting using bootstrap validation. Mean prostate stiffness on the logarithmic scale (p = 0.015) and standardized Z-scores (p = 0.025) were both significant predictors of cancer. This study concludes that stiffness measured by the tactile resonance sensor is a significant predictor of prostate cancer with potential for future development towards a clinical instrument for surgical guidance.

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  • 17.
    Lindahl, Olof A
    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).
    Ramser, K.
    Bäcklund, Tomas
    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).
    Ljungberg, Börje
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Urology and Andrology.
    Bergh, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Prostate cancer detection ex vivo combining Raman spectroscopy and tactile resonance technology2018In: EMBEC & NBC 2017 / [ed] Eskola, H Vaisanen, O Viik, J Hyttinen, J, SPRINGER-VERLAG SINGAPORE PTE LTD , 2018, p. 193-196Conference paper (Refereed)
    Abstract [en]

    Prostate cancer is the most common cancer for men in the western world. The most prevalent curative treatment is radical prostatectomy. However, prostate surgery can give unwanted side effects and there is a need for an instrument that can provide decision support to the surgeon during surgery on the presence of cancer cells in the surgical margin. A dual modality probe, combining Raman spectroscopy and tactile resonance technology, has been used for detecting cancer in fresh human prostate tissue. The tactile resonance modality measures the tissue stiffness and Raman spectroscopy depicts the molecular content in tissue, both related to cancer. After ethical approval, the study investigated the potential of the dual-modality probe by testing its ability to differentiate between normal and cancerous prostate tissue ex vivo. It also investigated the minimal amount of measurement points needed to securely detect cancer on the surface of prostate tissue. Measurements on three prostate tissue slices show that the tactile resonance modality measuring stiffness was able to detect differences between normal and cancerous tissue on a significant level of 90%, but the sample size was too low to draw any firm conclusions. It was also suggested from the study results that the high wavenumber region in the Raman spectrum can give valuable information about cancer in prostate tissue. A number of 24 measurement points were enough for detecting cancer in prostate slices in this study. It can be suggested from this study that combining these two sensor modalities is promising for accurate detection of prostate cancer that is needed during prostate surgery, but more measurements including more prostates must be performed before the full value of the study result can be established.

  • 18.
    Öhberg, Fredrik
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Bäcklund, Tomas
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Sundström, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grip, Helena
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Portable Sensors Add Reliable Kinematic Measures to the Assessment of Upper Extremity Function2019In: Sensors, E-ISSN 1424-8220, Vol. 19, no 5, article id 1241Article in journal (Refereed)
    Abstract [en]

    Ordinal scales with low resolution are used to assess arm function in clinic. These scales may be improved by adding objective kinematic measures. The aim was to analyze within-subject, inter-rater and overall reliability (i.e., including within-subject and inter-rater reliability) and check the system's validity of kinematic measures from inertial sensors for two such protocols on one person. Twenty healthy volunteers repeatedly performed two tasks, finger-to-nose and drinking, during two test sessions with two different raters. Five inertial sensors, on the forearms, upper arms and xiphoid process were used. Comparisons against an optical camera system evaluated the measurement validity. Cycle time, range of motion (ROM) in shoulder and elbow were calculated. Bland-Altman plots and linear mixed models including the generalizability (G) coefficient evaluated the reliability of the measures. Within-subject reliability was good to excellent in both tests (G = 0.80-0.97) and may serve as a baseline when assessing upper extremities in future patient groups. Overall reliability was acceptable to excellent (G = 0.77-0.94) for all parameters except elbow axial rotation in finger-to-nose task and both elbow axial rotation and flexion/extension in drinking task, mainly due to poor inter-rater reliability in these parameters. The low to good reliability for elbow ROM probably relates to high within-subject variability. The sensors provided good to excellent measures of cycle time and shoulder ROM in non-disabled individuals and thus have the potential to improve today's assessment of arm function.

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