| 1. |
- Abbaspour Asadollah, Sara, et al.
(författare)
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Evaluation of surface EMG-based recognition algorithms for decoding hand movements
- 2019
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Ingår i: Medical and Biological Engineering and Computing. - : Springer. - 0140-0118 .- 1741-0444. ; 58:1, s. 83-100
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Tidskriftsartikel (refereegranskat)abstract
- Myoelectric pattern recognition (MPR) to decode limb movements is an important advancement regarding the control of powered prostheses. However, this technology is not yet in wide clinical use. Improvements in MPR could potentially increase the functionality of powered prostheses. To this purpose, offline accuracy and processing time were measured over 44 features using six classifiers with the aim of determining new configurations of features and classifiers to improve the accuracy and response time of prosthetics control. An efficient feature set (FS: waveform length, correlation coefficient, Hjorth Parameters) was found to improve the motion recognition accuracy. Using the proposed FS significantly increased the performance of linear discriminant analysis, K-nearest neighbor, maximum likelihood estimation (MLE), and support vector machine by 5.5%, 5.7%, 6.3%, and 6.2%, respectively, when compared with the Hudgins’ set. Using the FS with MLE provided the largest improvement in offline accuracy over the Hudgins feature set, with minimal effect on the processing time. Among the 44 features tested, logarithmic root mean square and normalized logarithmic energy yielded the highest recognition rates (above 95%). We anticipate that this work will contribute to the development of more accurate surface EMG-based motor decoding systems for the control prosthetic hands. [Figure not available: see fulltext.].
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| 2. |
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| 3. |
- Albinsson, John, et al.
(författare)
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A combination of parabolic and grid slope interpolation for 2D tissue displacement estimations
- 2017
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Ingår i: Medical & Biological Engineering & Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 55:8, s. 1327-1338
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Tidskriftsartikel (refereegranskat)abstract
- Parabolic sub-sample interpolation for 2D block-matching motion estimation is computationally efficient. However, it is well known that the parabolic interpolation gives a biased motion estimate for displacements greater than |y.2| samples (y = 0, 1, …). Grid slope sub-sample interpolation is less biased, but it shows large variability for displacements close to y.0. We therefore propose to combine these sub-sample methods into one method (GS15PI) using a threshold to determine when to use which method. The proposed method was evaluated on simulated, phantom, and in vivo ultrasound cine loops and was compared to three sub-sample interpolation methods. On average, GS15PI reduced the absolute sub-sample estimation errors in the simulated and phantom cine loops by 14, 8, and 24% compared to sub-sample interpolation of the image, parabolic sub-sample interpolation, and grid slope sub-sample interpolation, respectively. The limited in vivo evaluation of estimations of the longitudinal movement of the common carotid artery using parabolic and grid slope sub-sample interpolation and GS15PI resulted in coefficient of variation (CV) values of 6.9, 7.5, and 6.8%, respectively. The proposed method is computationally efficient and has low bias and variance. The method is another step toward a fast and reliable method for clinical investigations of longitudinal movement of the arterial wall.
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| 4. |
- Andersson, Kennet, et al.
(författare)
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Real-time estimation of cerebrospinal fluid system parameters via oscillating pressure infusion
- 2010
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Ingår i: Medical and Biological Engineering and Computing. - : Springer. - 0140-0118 .- 1741-0444. ; 48:11, s. 1123-1131
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Tidskriftsartikel (refereegranskat)abstract
- Hydrocephalus is related to a disturbed cerebrospinal fluid (CSF) system. For diagnosis, lumbar infusion test are performed to estimate outflow conductance, C (out), and pressure volume index, PVI, of the CSF system. Infusion patterns and analysis methods used in current clinical practice are not optimized. Minimizing the investigation time with sufficient accuracy is of major clinical relevance. The aim of this study was to propose and experimentally evaluate a new method, the oscillating pressure infusion (OPI). The non-linear model of the CSF system was transformed into a linear time invariant system. Using an oscillating pressure pattern and linear system identification methods, C (out) and PVI with confidence intervals, were estimated in real-time. Forty-two OPI and constant pressure infusion (CPI) investigations were performed on an experimental CSF system, designed with PVI = 25.5 ml and variable C (out). The ARX model robustly estimated C (out) (mean C (out,OPI) - C (out,CPI) = 0.08 μl/(s kPa), n = 42, P = 0.68). The Box-Jenkins model proved most reliable for PVI (23.7 ± 2.0 ml, n = 42). The OPI method, with its oscillating pressure pattern and new parameter estimation methods, efficiently estimated C (out) and PVI as well as their confidence intervals in real-time. The results from this experimental study show potential for the OPI method and supports further evaluation in a clinical setting.
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| 5. |
- Andersson, Nina, et al.
(författare)
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Adaptive method for assessment of cerebrospinal fluid outflow conductance.
- 2007
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 45:4, s. 337-343
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Tidskriftsartikel (refereegranskat)abstract
- Outflow conductance (C out) is important for predicting shunt responsiveness in patients with suspected idiopathic adult hydrocephalus syndrome (IAHS). C out is determined by performing an infusion test into the cerebrospinal fluid system, and the reliability of the test is dependent on the measurement time. The objective of this study was to develop an adaptive signal analysis method to reduce the investigation time, by taking the individual intracranial pressure variations of the patient into consideration. The method was evaluated on 28 patients with suspected IAHS. The results from full time investigations (60 min) were compared to the results of the new algorithm. Applying the new adaptive method resulted in a reduction of mean investigation time by 14.3 ± 5.9 min (mean ± SD), p < 0.01. The reduction of reliability in the C out estimation was found clinically negligible. We thus recommend this adaptive method to be used when performing constant pressure infusion tests.
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| 6. |
- Arildsson, Mikael, et al.
(författare)
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Spectral signature and heterodyne efficiency for different wavelengths in laser Doppler flowmetry
- 2002
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 40:1, s. 85-89
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Tidskriftsartikel (refereegranskat)abstract
- Laser Doppler perfusion monitoring and imaging technologies generate time traces and two-dimensional flow maps of the microcirculation. With the goal of reaching different tissue depths, these technologies are equipped with lassers operating at different wavelengths λ. The fact that the average scattering angle, at a single scattering event, between a photon and a red blood cell increases with λ is compensated for by a 1/λ effect in the scattering vector, rendering the average frequency shift virtually independent of the choice of wavelength. Monte Carlo simulations showed that the corresponding spectral signature of the Doppler signals for λ=632.8nm and 780nm were close to identical. The theoretical predictions were verified by calculating the centre-of-gravity (COG) frequency of the laser Doppler power spectral density for the two wavelengths from forearm and finger skin, representing a low and high perfusion area, respectively (forearm COG=123 against 121Hz, finger COG=220 against 212 Hz). When the wavelength changes from 632.8nm to 780nm, the heterodyne efficiency of the detector and, thereby, the inherent system amplifcation increase. For tissues with identical microvascular flow conditions, the output signal therfore tends to increase in magnitude when shifting to longer wavelengths.
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| 7. |
- Ask, Per, et al.
(författare)
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Accuracy and choice of procedures in 24-hour oesophageal pH monitoring with monocrystalline antimony electrodes.
- 1986
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 24:6, s. 602-608
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Tidskriftsartikel (refereegranskat)abstract
- In 24 h pH monitoring, the evaluation is dependent on the absolute accuracy of the pH measurements. Several sources of error exist, such as the chemical composition of calibration buffers and reference electrode gel and the effect of temperature on both the pH and the reference electrodes. We investigated the magnitude of these errors for the monocrystalline antimony electrode. Similar analysis applies to other types of pH electrodes. The errors we found are important when choosing a calibration procedure. We recommend a calibration procedure in which the pH and reference electrodes are both put in a beaker with the calibration buffers prior to and after the 24 h measurements. The calibration buffers and the electrode gel should have a specially selected ion composition where, for example, the Cl-ion concentration is critical. Corrections for differences in temperature between the calibration and the in situ measurements must be added. The pH measurements can be checked by performing in situ calibration.
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| 8. |
- Ask, Per, et al.
(författare)
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Bio-acoustic signals from stenotic tube flow : state of the art and perspectives for future methodological development.
- 1995
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 33:5, s. 669-675
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Tidskriftsartikel (refereegranskat)abstract
- To study the degree of stenosis from the acoustic signal generated by the turbulent flow in a stenotic vessel, so-called phonoangiography was first suggested over 20 years ago. A reason for the limited use of the technique today may be that, in the early work, the theory of how to relate the spectrum of the acoustic signal to the degree of the stenosis was not clear. However, during the last decade, the theoretical basis for this and other biological tube flow applications has been clarified. Now there is also easy access to computers for frequency analysis. A further explanation for the limited diagnostic use of bio-acoustic techniques for tube flow is the strong competition from ultrasound Doppler techniques. In the future, however, applications may be expected in biological tube flow where the non-invasive, simple and inexpensive bio-acoustic techniques will have a definite role as a diagnostic method.
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| 9. |
- Ask, Per, 1950-, et al.
(författare)
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Bioacoustic signals from stenotic tube flow
- 1995
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Ingår i: Medical & Biological Engineering & Computing. - : Springer. - 0140-0118 .- 1741-0444. ; 33, s. 669-675
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Ask, Per, et al.
(författare)
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Combined pH and pressure measurement device for oesophageal investigations.
- 1981
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 19:4, s. 443-446
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Tidskriftsartikel (refereegranskat)abstract
- A combined pH- and pressure-measurement device for oesophageal investigations has been designed using monocrystalline antimony pH electrodes and perfused polyvinyl catheters. The combined device facilitates pressure measurements simultaneously with pH recording, both distal and proximal to the pH electrode. The device is easier to pass through the nose to the oesophagus than the conventional glass pH electrode. pH and pressure measurements in the oesophagus are therefore simplified and valuable information about the function of the region of the lower oesophageal sphincter is added owing to the simultaneous recording of the two parameters.
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