Current Issue : July - September Volume : 2018 Issue Number : 3 Articles : 5 Articles
Background: In longitudinal electroencephalography (EEG) studies, repeatable\nelectrode positioning is essential for reliable EEG assessment. Conventional methods\nuse anatomical landmarks as fiducial locations for the electrode placement. Since the\nlandmarks are manually identified, the EEG assessment is inevitably unreliable because\nof individual variations among the subjects and the examiners. To overcome this unreliability,\nan augmented reality (AR) visualization-based electrode guidance system was\nproposed.\nMethods: The proposed electrode guidance system is based on AR visualization to\nreplace the manual electrode positioning. After scanning and registration of the facial\nsurface of a subject by an RGB-D camera, the AR of the initial electrode positions as reference\npositions is overlapped with the current electrode positions in real time. Thus, it\ncan guide the position of the subsequently placed electrodes with high repeatability.\nResults: The experimental results with the phantom show that the repeatability of\nthe electrode positioning was improved compared to that of the conventional 10ââ?¬â??20\npositioning system.\nConclusion: The proposed AR guidance system improves the electrode positioning\nperformance with a cost-effective system, which uses only RGB-D camera. This system\ncan be used as an alternative to the international 10ââ?¬â??20 system....
Background: Cerebrovascular events are frequently associated with hemodynamic\ndisturbance caused by internal carotid artery (ICA) stenosis. It is challenging to determine\nthe ischemia-related carotid stenosis during the intervention only using digital\nsubtracted angiography (DSA). Inspired by the performance of well-established FFRct\ntechnique in hemodynamic assessment of significant coronary stenosis, we introduced\na pressure-based carotid arterial functional assessment (CAFA) index generated from\ncomputational fluid dynamic (CFD) simulation in DSA data, and investigated its feasibility\nin the assessment of hemodynamic disturbance preliminarily using pressure-wired\nmeasurement and arterial spin labeling (ASL) MRI as references.\nMethods: The cerebral multi-delay multi-parametric ASL-MRI and carotid DSA including\ntrans-stenotic pressure-wired measurement were implemented on a 65-year-old\nman with asymptomatic unilateral (left) ICA stenosis. A CFD simulation using simplified\nboundary condition was performed in DSA data to calculate the CAFA index. The\ncerebral blood flow (CBF) and arterial transit time (ATT) of ICA territories were acquired.\nResults: CFD simulation showed good correlation (r = 0.839, P = 0.001) with slight systematic\noverestimation (mean difference âË?â?? 0.007, standard deviation 0.017) compared\nwith pressure-wired measurement. No significant difference was observed between\nthem (P = 0.09). Though the narrowing degree of in the involved ICA was about 70%,\nthe simulated and measured CAFA (0.942/0.937) revealed a functionally nonsignificant\nstenosis which was also verified by a compensatory final CBF (fronto-temporal/frontoparietal\nregion: 51.58/45.62 ml/100 g/min) and slightly prolonged ATT (1.23/1.4 s)\nin the involved territories, together with a normal leftââ?¬â??right percentage difference\n(2.1ââ?¬â??8.85%).\nConclusions: The DSA based CFD simulation showed good consistence with invasive\napproach and could be used as a cost-saving and efficient way to study the\nrelationship between hemodynamic disorder caused by ICA stenosis and subsequent\nperfusion variations in brain. Further research should focus on the role of noninvasive\npressure-based CAFA in screening asymptomatic ischemia-causing carotid stenosis....
Background: Many studies have demonstrated that the geometry of the carotid\nbifurcation enables prediction of blood flow variation associated with atherosclerotic\nplaque formation. The phase angle between the arterial wall circumferential strain and\nits instantaneous wall shear stress is known as stress phase angle (SPA). This parameter\nis used to evaluate hemodynamic factors of atherogenesis. Note that SPA can be\nnumerically computed for the purpose of locating atherosclerosis in different artery\ngeometries. However, there is no experimental data to verify its role in the location of\natherosclerosis in different artery geometries. In this study, we use an ultrasonic biomechanical\nmethod to experimentally evaluate the role of SPA for locating atherosclerosis\nin carotid bifurcation.\nResults: For carotid anthropomorphic vascular phantom experiments, the SPAs\nof common carotid arteries (CCAs), external carotid arteries (ECAs) and internal\ncarotid arteries (ICAs) are âË?â?? 148.53 Ã?± 6.92Ã?°, âË?â?? 153.95 Ã?± 5.11Ã?°, and âË?â?? 238.69 Ã?± 1.72Ã?°,\nrespectively. The corresponding SPAs are âË?â?? 173.47 Ã?± 0.065Ã?°, âË?â?? 115.57 Ã?± 4.83Ã?° and\nâË?â?? 233.9 Ã?± 8.12Ã?° for the polyvinyl alcohol (PVA-c) phantoms. In vivo mouse experiments\nindicated that the wall shear stress and circumferential strain were out of phase in the\nICAs (âË?â?? 280.08 Ã?± 13.12Ã?°) to a greater extent as compared to CCAs (âË?â?? 141.97 Ã?± 8.03Ã?°)\nand ECAs (âË?â?? 170.07 Ã?± 9.24Ã?°).\nConclusions: The results suggested that SPA may be a useful indicator to locate the\natherosclerosis position in carotid bifurcation....
Background: The present study contrasts the accuracy of different reconstructed\nmodels with distinctive segmentation methods performed by various experts. Seven\nresearch groups reconstructed nine 3D models of one human femur based on an\nacquired CT image using their own computational methods. As a reference model for\naccuracy assessment, a 3D surface scan of the human femur was created using an optical\nmeasuring system. Prior to comparison, the femur was divided into four areas; ââ?¬Å?neck\nand greater trochanterââ?¬Â, ââ?¬Å?proximal metaphysisââ?¬Â, ââ?¬Å?diaphysisââ?¬Â, and ââ?¬Å?distal metaphysisââ?¬Â. The\ndeviation analysis was carried out in GEOMAGIC studio v.2013 software.\nResults: The results revealed that the highest deviation errors occurred in ââ?¬Å?neck and\ngreater trochanterââ?¬Â area and ââ?¬Å?proximal metaphysisââ?¬Â area with RMSE of 0.84 and 0.83 mm\nrespectively.\nConclusion: In conclusion, this study shows that the average deviation of reconstructed\nmodels prepared by experts with various methods, skills and software from\nthe surface 3D scan is lower than 0.79 mm, which is not a significant discrepancy...
Background: Most of the objective and quantitative methods proposed for spasticity\nmeasurement are not suitable for clinical application, and methods for surface electromyography\n(sEMG) signal processing are mainly limited to the time-domain. This study\naims to quantify muscle activity in the timeââ?¬â??frequency domain, and develop a practical\nclinical method for the objective and reliable evaluation of the spasticity based on\nthe Hilbertââ?¬â??Huang transform marginal spectrum entropy (HMSEN) and the root mean\nsquare (RMS) of sEMG signals.\nMethods: Twenty-six stroke patients with elbow flexor spasticity participated in\nthe study. The subjects were tested at sitting position with the upper limb stretched\ntowards the ground. The HMSEN of the sEMG signals obtained from the biceps brachii\nwas employed to facilitate the stretch reflex onset (SRO) detection. Then, the difference\nbetween the RMS of a fixed-length sEMG signal obtained after the SRO and the RMS of\na baseline sEMG signal, denoted as the RMS difference (RMSD), was employed to evaluate\nthe spasticity level. The relations between Modified Ashworth Scale (MAS) scores\nand RMSD were investigated by Ordinal Logistic Regression (OLR). Goodness-of-fit of\nthe OLR was obtained with Hosmerââ?¬â??Lemeshow test.\nResults: The HMSEN based method can precisely detect the SRO, and the RMSD\nscores and the MAS scores were fairly well related (test: Ãâ?¡2 = 8.8060, p = 0.2669; retest:\nÃâ?¡2 = 1.9094, p = 0.9647). The prediction accuracies were 85% (test) and 77% (retest)\nwhen using RMSD for predicting MAS scores. In addition, the testââ?¬â??retest reliability was\nhigh, with an interclass correlation coefficient of 0.914 and a standard error of measurement\nof 1.137. Blandââ?¬â??Altman plots also indicated a small bias.\nConclusions: The proposed method is manually operated and easy to use, and\nthe HMSEN based method is robust in detecting SRO in clinical settings. Hence, the\nmethod is applicable to clinical practice. The RMSD can assess spasticity in a quantitative\nway and provide greater resolution of spasticity levels compared to the MAS\nin clinical settings. These results demonstrate that the proposed method could be clinically more useful for the accurate and reliable assessment of spasticity and may be\nan alternative clinical measure to the MAS....
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