第12次 아시아ㆍ太平洋 矯政局長會議 參加記

The wavelet transform has emerged over recent years as a powerful time-frequency analysis and signal coding tool favoured for the interrogation of complex nonstationary signals. Its application to biosignal processing has been at the forefront of these developments where it has been found particularly useful in the study of these, often problematic, signals: none more so than the ECG. In this review, the emerging role of the wavelet transform in the interrogation of the ECG is discussed in detail, where both the continuous and the discrete transform are considered in turn.

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Wavelet transforms and the ECG: a review.

Auditory selective attention is an important mechanism for top-down selection of the vast amount of auditory information our perceptual system is exposed to. In the present study, the impact of attention on auditory steady-state responses is investigated. This issue is still a matter of debate and recent findings point to a complex pattern of attentional effects on the auditory steady state response (aSSR). The present study aimed at shedding light on the involvement of ipsilateral and contralateral activations to the attended sound taking into account hemispheric differences and a possible dependency on modulation frequency. In aid of this, a dichotic listening experiment was designed using amplitude-modulated tones that were presented to the left and right ear simultaneously. Participants had to detect target tones in a cued ear while their brain activity was assessed using MEG. Thereby, a modulation of the aSSR by attention could be revealed, interestingly restricted to the left hemisphere and 20 Hz responses: contralateral activations were enhanced while ipsilateral activations turned out to be reduced. Thus, our findings support and extend recent findings, showing that auditory attention can influence the aSSR, but only under specific circumstances and in a complex pattern regarding the different effects for ipsilateral and contralateral activations.

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Top-down modulation of the auditory steady-state response in a task-switch paradigm.

Laser Doppler Vibrometry: Development of advanced solutions answering to technology's needs

In spite of the facts that magnetic resonance spectroscopy (MRS) is applied as clinical tool in non-specialized institutions and that semi-automatic acquisition and processing tools can be used to produce quantitative information from MRS exams without expert information, issues of spectral quality and quality assessment are neglected in the literature of MR spectroscopy. Even worse, there is no consensus among experts on concepts or detailed criteria of quality assessment for MR spectra. Furthermore, artifacts are not at all conspicuous in MRS and can easily be taken for true, interpretable features. This article aims to increase interest in issues of spectral quality and quality assessment, to start a larger debate on generally accepted criteria that spectra must fulfil to be clinically and scientifically acceptable, and to provide a sample gallery of artifacts, which can be used to raise awareness for potential pitfalls in MRS.

Issues of spectral quality in clinical 1H-magnetic resonance spectroscopy and a gallery of artifacts

Evaluation of measurement uncertainty is considered when the value of the measurand depends on the continuous variable time. A concept of dynamic measurement uncertainty is introduced by generalizing the GUM approach. The concept is applied to linear and time-invariant systems which are often appropriate to model dynamic measurements. Digital filtering is proposed for estimating the time-dependent value of the measurand and the design of an appropriate FIR filter is described. Dynamic uncertainty evaluation is then carried out for this analysis and conditions are specified for its proper use. The approach is illustrated for the particular example of a second-order model. It is shown in terms of simulations that the proposed analysis yields significantly improved results when compared with the sometimes applied quasi-static treatment.

https://iopscience.iop.org/article/10.1088/0026-1394/45/4/013/pdf

Uncertainty evaluation for dynamic measurements modelled by a linear time-invariant system

To assess the applicability of magnetic resonance spectroscopy (MRS) for long-term follow-up of neurological diseases a longitudinal 1H-MRS study at 3 T was carried out on ten patients having relapsing-remitting multiple sclerosis (MS) who, after baseline examination, received interferon-β (IFN) lb. At 8–20 examinations within up to 34 months absolute concentrations ofN-acetylaspartate (NAA), total creatine (tG), and choline-containing compounds (tCho) were determined in a large non-enhancing lesion and contralateral normal appearing white matter (NAWM). MR spectra were analyzed using a novel time domain-frequency domain method including non-parametric background characterization. For comparison at baseline, ten healthy controls were examined. The concentrations of tCho and tCr were found to be higher in MS brain than in control brain. Besides a non-significantly lower NAA concentration in lesions there were no concentration differences between lesions and NAWM. Over the follow-up period the measured metabolite concentrations exhibited a high variability. Most concentrations remained within this scatter, and statistical tests revealed significant fluctuations in the levels of metabolites in one case only. This stability of the metabolite concentrations over time might result from IFN therapy as for the spontaneous course of relapsing-remitting MS decreasing metabolite (NAA/tCr) ratios have been reported. The results further suggest that future treatment trials intending to use metabolite concentrations as a secondary outcome indicator use even longer observation periods and, besides group analysis of large cohorts, investigate the time behavior of selected single cases. The biochemical abnormalities found in NAWM emphasize the importance of analyzing both lesion and NAWM.

Serial 1H-MRS in relapsing-remitting multiple sclerosis: effects of interferon-β therapy on absolute metabolite concentrations

The task of analysing dynamic measurements is considered for the case that the input–output behaviour of the employed sensor can be described in terms of a second-order dynamic model. It is assumed that estimates of the parameters of this model are available which have been determined by the analysis of previous dynamic calibration measurements. The goal is to estimate the unknown input of the sensor given its discrete-time output signal. It is proposed to apply an FIR filter which is constructed according to the underlying dynamic model. The uncertainties associated with the obtained estimates of the time-dependent measurand are then determined by taking into account the uncertainty associated with the estimates of the parameters of the dynamic model, the uncertainty of the sensor's output signal and the applied signal processing steps. The proposed procedure allows real-time calculations including the real-time calculation of uncertainties, and it could therefore be directly integrated into the measurement chain. Utilizing dynamic calibration measurements of accelerometers, the proposed analysis is demonstrated by its application to acceleration measurements upon shock excitations.

https://iopscience.iop.org/article/10.1088/0957-0233/18/12/002/pdf

Analysis of dynamic measurements and determination of time-dependent measurement uncertainty using a second-order model

Pooling information from multiple, independent studies (meta-analysis) adds great value to medical research Random effects models are widely used for this purpose However, there are many different ways of estimating model parameters, and the choice of estimation procedure may be influential upon the conclusions of the meta-analysis In this paper, we describe a recently proposed Bayesian estimation procedure and compare it with a profile likelihood method and with the DerSimonian-Laird and Mandel-Paule estimators including the Knapp-Hartung correction The Bayesian procedure uses a non-informative prior for the overall mean and the between-study standard deviation that is determined by the Berger and Bernardo reference prior principle The comparison of these procedures focuses on the frequentist properties of interval estimates for the overall mean The results of our simulation study reveal that the Bayesian approach is a promising alternative producing more accurate interval estimates than those three conventional procedures for meta-analysis The Bayesian procedure is also illustrated using three examples of meta-analysis involving real data Copyright © 2016 John Wiley & Sons, Ltd

Bayesian estimation in random effects meta‐analysis using a non‐informative prior

At the Physikalisch-Technische Bundesanstalt (PTB), a self-calibration method for the fast and precise in situ calibration of angle encoders without recourse to external reference standards has been developed. It relies on a suitable geometric arrangement of multiple reading heads which read out the radial grating of the angle encoder at different angular positions. Fourier-based algorithms are used to analyse the measurement differences of pairs of heads to recover the graduation error of the grating. A comprehensive overview, both theoretical and experimental, of the capabilities and limitations of the self-calibration method is presented, including experimental data obtained with the high-precision primary angle standard of PTB. The evaluation and, where it is possible, correction of error influences due to lateral shifts of the centre of the encoder's grating during its rotation, including its eccentricity, the reading heads' angular positions, and their non-uniform response, are discussed in detail, as well as the resulting uncertainty budget.

https://iopscience.iop.org/article/10.1088/0957-0233/25/5/055003/pdf

Alfred Link

Papers

Uncertainty evaluation for dynamic measurements modelled by a linear time-invariant system

Serial 1H-MRS in relapsing-remitting multiple sclerosis: effects of interferon-β therapy on absolute metabolite concentrations

Analysis of dynamic measurements and determination of time-dependent measurement uncertainty using a second-order model

Bayesian estimation in random effects meta‐analysis using a non‐informative prior

Capabilities and limitations of the self-calibration of angle encoders