| 1. |
- Grönlund, Christer, et al.
(författare)
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Imaging two-dimensional mechanical waves of skeletal muscle contraction
- 2013
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629 .- 1879-291X. ; 39:2, s. 360-369
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Grönlund, Christer, et al.
(författare)
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Simultaneous quantification of myocardial and blood flow velocities based on duplex mode ultrasound imaging
- 2013
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Ingår i: Biomedical engineering online. - : BioMed Central (BMC). - 1475-925X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 3. |
- Stubenrauch, Cosima, et al.
(författare)
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Aqueous foams stabilized by n-dodecyl-beta-D-maltoside, hexaethyleneglycol monododecyl ether, and their 1 : 1 mixture
- 2009
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 5:16, s. 3070-3080
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous foams stabilized by the non-ionic surfactants n-dodecyl-beta-D-maltoside (beta-C(12)G(2)) and hexaethyleneglycol monododecyl ether (C12E6) as well as by their 1 : 1 mixture were studied as a function of the total surfactant concentration from 0.1 to 10 cmc. Foamability and foam stability were measured with home-built winding equipment, the commercially available FoamScan, and a home-built foam conductivity apparatus (FCA), respectively. It was found that the foamability increases with increasing surfactant concentration for both the single and the mixed surfactant systems. On the other hand, at a fixed relative surfactant concentration (c/cmc) the foamability of beta-C(12)G(2) solutions was found to be much higher than that of C12E6 solutions, while the 1 : 1 mixture behaves like the pure C12E6. Measurements at different gas (N-2) flow rates have shown that the foamability decreases non-linearly with decreasing N-2 flow rate, which shows that foam generation and foam breakdown occur simultaneously. Regarding foam stability it was found that it also increases with increasing surfactant concentration. As was the case for the foamability, the stability of foams stabilized by beta-C(12)G(2) was much higher than that of foams stabilized by C12E6, while the foam stability of the 1 : 1 mixture was comparable to that of the pure C12E6. The foam results are discussed in the light of static surface tensions, dynamic surface tensions, and surface elasticities, which were measured for the single and the mixed surfactant systems.
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| 4. |
- Öhberg, Fredrik, 1969-, et al.
(författare)
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Home-based system for recording pulmonary function and disease-related symptoms in patients with chronic obstructive pulmonary disease, COPD : a pilot study
- 2016
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Ingår i: SM Journal of Pulmonary Medicine. - : SM Group. - 2574-240X. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Many patients with Chronic Obstructive Pulmonary Disease (COPD) suffer from acute exacerbations characterized by an increase in symptoms beyond normal day-to-day variation. The prognosis of patients with frequent exacerbations is poor and effort to curb these worsening episodes has great potential to improve the patient’s quality of life and to reduce associated costs. Telemonitoring has been proposed as a promising strategy in this respect. However, information on what physical signs or symptoms that should be recorded and how recorded data should be interpreted is largely missing in the literature.Methods: A new home-based system, based on a tablet computer, which can guide COPD patients to perform spirometry (inspiratory capacity, IC and forced expiratory volume in one and six seconds, FEV1 and FEV6) and record symptoms (COPD assessment test, CAT) was developed. The system was evaluated for 8-12 weeks in four patients with moderate to severe COPD with the aims to; i) assess the feasibility of the system to be used unsupervised by COPD patients and, ii) to evaluate the quality and ability of recorded parameters to reveal early signs of an exacerbation. Pearson bivariate correlation was performed between all outcome measures and descriptive information about inherent subject properties were presented.Results: The system was well accepted by all study subjects and the study generated a total of 253 measurements of which 94.5% were considered acceptable for analysis. One of the subjects developed an acute exacerbation towards the end of the study, whereas the other three subjects remained stable. Descriptive analysis of the data suggest that trends in the CAT score may indicate changes in health status and that IC tends to be more responsive to these changes compared to FEV1.Conclusion: The system developed in this study is well suited to be used unsupervised by COPD patients. Recorded data, in particular CAT, may be sensitive enough to detect early signs of an acute COPD exacerbation, although more data is needed to fully resolve the nature of such an association.
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