| 1. |
- Löfhede, Johan, 1978, et al.
(författare)
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Comparison of Three Methods for Classifying Burst and Suppression in the EEG of Post Asphyctic Newborns
- 2007
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Ingår i: Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE. - : IEEE. - 1557-170X. - 9781424407880 - 9781424407873 ; , s. 5136-5139
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Konferensbidrag (refereegranskat)abstract
- Fisher's linear discriminant, a feed-forward neural network (NN) and a support vector machine (SVM) are compared with respect to their ability to distinguish bursts from suppression in burst-suppression electroencephalogram (EEG) signals using five features inherent in the EEG as input. The study is based on EEG signals from six full term infants who have suffered from perinatal asphyxia, and the methods have been trained with reference data classified by an experienced electroencephalographer. The results are summarized as area under the curve (AUC) values derived from receiver operating characteristic (ROC) curves for the three methods, and show that the SVM is slightly better than the others, at the cost of a higher computational complexity.
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| 2. |
- Corino, V. D. A., et al.
(författare)
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A Gaussian mixture model for time-frequency analysis during atrial fibrillation electrocardiograms
- 2007
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Ingår i: 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS 2007.. - 1557-170X. - 9781424407880 ; , s. 271-274
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Konferensbidrag (refereegranskat)abstract
- During atrial fibrillation (AF), time-frequency analysis of atrial signal has been applied to describe fibrillatory frequency trends. Recently, temporal changes in spectral shape have been investigated using the spectral profile technique. This profile is computed recursively by fitting each short-time log-spectrum to a spectral template, using amplitude scaling and frequency shifting. The purpose of the present study was to develop a Gaussian mixture model of the spectral profile in order to characterize the shape of AF waveforms. A novel index is introduced, the so-called harmonic index (HI), which reflects properties of the fundamental frequency peak and related harmonics peaks as estimated from the model. The index was tested on recordings from 9 patients with persistent AF, obtained before and after exercise testing. The HI succeeded in monitoring the response to exercise, i.e. change in the spectral profile to a less harmonic pattern, which is consistent with a reduction in AF organization (HI: 0.61±0.11 vs. 0.50±0.19, rest vs. exercise; p≪0.05).
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| 3. |
- Wårdell, Karin, 1959-, et al.
(författare)
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A laser Doppler system for intracerebral measurements during stereotactic neurosurgery
- 2007
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Ingår i: Engineering in Medicine and Biology Society, 2007. EMBS 2007. - : IEEE. - 9781424407873 - 9781424407880 ; , s. 4083-4086
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Konferensbidrag (refereegranskat)abstract
- A laser Doppler system for intracerebral measurements during stereotactic and functional neurosurgery is presented. The system comprises a laser Doppler perfusion monitor, an optical probe adapted for the Leksellreg stereotactic system and a personal computer with software for acquisition, data analysis and presentation. The software makes it possible to present both the perfusion and the total backscattered light intensity (TLI) in real-time. During intracerebral measurements, the perfusion signal records the tissue's microcirculation whereas the TLI signal may be used to distinguish between grey and white matter. Evaluation of the system has been done during stereotactic neurosurgery in relation to implantation of deep brain stimulation electrodes. Measurements were made along trajectories towards targets in the deep brain structure as well as in pre-calculated target areas. The measurements show that the system has a potential to be used for intracerebral guidance but further evaluation of the technique is needed.
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| 4. |
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| 5. |
- Abualhoul, Mohammad Y., et al.
(författare)
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Free space optical link for biomedical applications
- 2012
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Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. - 9781424441198 ; , s. 1667-1670
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Konferensbidrag (refereegranskat)abstract
- Free space optics is an interesting alternative for telemetry with medical implants, due to the high data bandwidths available at optical frequencies. Especially implanted brain-computer interfaces gives rise to large data sets that needs to be transmitted transcutaneous. In this paper we show that it is possible to establish such a link at near-IR wavelengths using a modulated reflector in the implant, thus keeping the laser and the detector on the outside. In addition, we show that it will not only work on short, i.e. touch, distances but also at larger distances, in the range of a meter. We have used an electro absorption modulator to modulate the reflection of an external laser source back towards an external detector. The only part of this system that needs to be implanted is the modulator and drive electronics. The study has been done both by Monte-Carlo simulations of a multi-layer model of a rat skull, and with an experiment demonstrating the feasibility of the link when transmitted through biological tissue. The results show that it is possible to establish a transcutaneous link with an external laser source and light detector, and an internal modulated reflector.
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| 6. |
- Ahkami, Bahareh, 1994, et al.
(författare)
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Probability-Based Rejection of Decoding Output Improves the Accuracy of Locomotion Detection During Gait
- 2023
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Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X.
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Konferensbidrag (refereegranskat)abstract
- Prosthetic users need reliable control over their assistive devices to regain autonomy and independence, particularly for locomotion tasks. Despite the potential for myoelectric signals to reflect the users' intentions more accurately than external sensors, current motorized prosthetic legs fail to utilize these signals, thus hindering natural control. A reason for this challenge could be the insufficient accuracy of locomotion detection when using muscle signals in activities outside the laboratory, which may be due to factors such as suboptimal signal recording conditions or inaccurate control algorithms.This study aims to improve the accuracy of detecting locomotion during gait by utilizing classification post-processing techniques such as Linear Discriminant Analysis with rejection thresholds. We utilized a pre-recorded dataset of electromyography, inertial measurement unit sensor, and pressure sensor recordings from 21 able-bodied participants to evaluate our approach. The data was recorded while participants were ambulating between various surfaces, including level ground walking, stairs, and ramps. The results of this study show an average improvement of 3% in accuracy in comparison with using no post-processing (p-value < 0.05). Participants with lower classification accuracy profited more from the algorithm and showed greater improvement, up to 8% in certain cases. This research highlights the potential of classification post-processing methods to enhance the accuracy of locomotion detection for improved prosthetic control algorithms when using electromyogram signals.Clinical Relevance-Decoding of locomotion intent can be improved using post-processing techniques thus resulting in a more reliable control of lower limb prostheses.
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| 7. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Assessment of Suspected Aortic Stenosis by Auto Mutual Information Analysis of Murmurs
- 2007
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Ingår i: Engineering in Medicine and Biology Society, 2007. EMBS 2007. - 9781424407873 ; , s. 1945-1948
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Konferensbidrag (refereegranskat)abstract
- Mild sclerotic thickening of the aortic valve affects 25% of the population, and the condition causes aortic valve stenosis (AS) in 2% of adults above 65 years. Echocardiography is today the clinical standard for assessing AS. However, a cost effective and uncomplicated technique that can be used for decision support in the primary health care would be of great value. In this study, recorded phonocardiographic signals were analyzed using the first local minimum of the auto mutual information (AMI) function. The AMI method measures the complexity in the sound signal, which is related to the amount of turbulence in the blood flow and thus to the severity of the stenosis. Two previously developed phonocardiographic methods for assessing AS severity were used for comparison, the murmur energy ratio and the sound spectral averaging technique. Twenty-nine patients with suspected AS were examined with Doppler echocardiography. The aortic jet velocity was used as a reference of AS severity, and it was found to correlate with the AMI method, the murmur energy ratio and the sound spectral averaging technique with the correlation coefficient R = 0.82, R = 0.73 and R = 0.76, respectively.
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| 8. |
- Alcaraz Martinez, Raul, et al.
(författare)
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Application of frequency and sample entropy to discriminate long-term recordings of paroxysmal and persistent atrial fibrillation
- 2010
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Ingår i: Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE. - 1557-170X. - 9781424441235 ; , s. 4558-4561
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Konferensbidrag (refereegranskat)abstract
- Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. At an early stage of the disease, AF may terminate spontaneously and is then referred to as paroxysmal AF. On the other hand, when external intervention is required for the arrhythmia to terminate, it is referred to as persistent AF. In this work, a method to discriminate between paroxysmal and persistent AF in the long-term ECGs is presented. The dominant frequency as well as the organization of the atrial activity are employed to characterize AF. The dominant atrial frequency (DAF) is estimated using hidden Markov model based frequency tracking, and organization is estimated by the sample entropy of the main atrial wave (MAW) and the first two harmonics, respectively. Long-term variations in DAF and organization from 50 ECG recordings were evaluated, showing that episodes of paroxysmal AF were consistently associated with lower DAF and organization of the MAW and the harmonics, than was persistent AF. Discrimination of paroxysmal and persistent AF resulted in classification rates of 84.1±26.1%, thus suggesting that it possible to discriminate between paroxysmal and persistent AF in patients without previously known AF history.
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| 9. |
- Alipoor, Mohammad, 1983, et al.
(författare)
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On High Order Tensor-based Diffusivity Profile Estimation
- 2013
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Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. - 9781457702167 ; , s. 93-96, s. 4-
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Konferensbidrag (refereegranskat)abstract
- Diffusion weighted magnetic resonance imaging (dMRI) is used to measure, in vivo, the self-diffusion of water molecules in biological tissues. High order tensors (HOTs) are used to model the apparent diffusion coefficient (ADC) profile at each voxel from the dMRI data. In this paper we propose: (i) A new method for estimating HOTs from dMRI data based on weighted least squares (WLS) optimization; and (ii) A new expression for computing the fractional anisotropy from a HOT that does not suffer from singularities and spurious zeros. We also present an empirical evaluation of the proposed method relative to the two existing methods based on both synthetic and real human brain dMRI data. The results show that the proposed method yields more accurate estimation than the competing methods.
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| 10. |
- Anderson, Rachele, et al.
(författare)
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Insights on Spectral Measures for HRV Based on a Novel Approach for Data Acquisition
- 2018
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Ingår i: Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings. - 1557-170X. ; 2018, s. 510-513
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present new insights on classical spectral measures for heart rate variability (HRV), based on a novel method for HRV acquisition. A dynamic breathing task, where the test participants are asked to breathe following a metronome with slowly increasing frequency, allows for the acquisition of respiratory-related HRV-data covering the frequency range in which adults breathe in different everyday situations. We discuss how the use of a time-frequency representation, e.g. the spectrogram or the Wigner-Ville distribution, should be preferred to the traditional use of the periodogram, due to the non-stationarity of the data. We argue that this approach can highlight the correlation of spectral measures such as low-frequency and high-frequency HRV with relevant factors as age, gender and Body-Mass-Index, thanks to the improved quality of the spectral measures.
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