Abstract:
:The ability to image the impedance changes that accompany neuronal depolarization in the brain would constitute a major advance in neuroscience technology. Unfortunately, these changes are likely to be small and rapid and so difficult to measure. The impedance change at frequencies above 10 kHz, as used by conventional EIT systems, may be estimated to be about 0.1%. Modelling indicates that a much larger impedance change of about 7% may occur with DC or very-low-frequency excitation. Difficulties with this approach include a low permissive current level and high electrode impedance. We constructed a prototype system employing square wave excitation at 5 Hz to evaluate such problems. It was tested in a saline-filled tank, recording 4000 frames s-1 at a current level of 50 microA. After averaging 100 sets of frames, the signal to noise ratio was 40-50 dB, and reciprocity errors were mostly 10-20%. Images of discrete resistivity changes of less than 10% could be obtained, but with significant systematic errors. While our prototype would not be suitable for neurophysiological imaging as it stands, it has enabled us to determine the modifications that would be required to construct a system for this application.
journal_name
Physiol Measjournal_title
Physiological measurementauthors
Boone KG,Holder DSdoi
10.1088/0967-3334/16/3a/009subject
Has Abstractpub_date
1995-08-01 00:00:00pages
A87-98issue
3 Suppl Aeissn
0967-3334issn
1361-6579journal_volume
16pub_type
杂志文章abstract::Arterial pCO2 is known to influence cerebral autoregulation but its effect on the dynamic relationship between mean arterial blood pressure (ABP) and mean cerebral blood flow velocity (CBFV), obtained from spontaneous fluctuations in ABP, has not been established. In 16 normal subjects, ABP was measured non-invasively...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/20/3/304
更新日期:1999-08-01 00:00:00
abstract:OBJECTIVE:In this research, we introduce a new methodology for atrial fibrillation (AF) diagnosis during sleep in a large population sample at risk of sleep-disordered breathing. APPROACH:The approach leverages digital biomarkers and recent advances in machine learning (ML) for mass AF diagnosis from overnight-hours o...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/abb8bf
更新日期:2020-11-06 00:00:00
abstract::Electrical impedance tomography (EIT) image reconstruction is an ill-posed problem requiring maximum measurement precision. Recent EIT systems claim 60 to 80 dB precision. Achieving higher values is hard in practice since measurements must be performed at relatively high frequency, on a living subject, while using com...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/27/5/S05
更新日期:2006-05-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/37/5/673
更新日期:2016-05-01 00:00:00
abstract::Conventional bioimpedance spectrometers measure resistance and reactance over a range of frequencies and, by application of a mathematical model for an equivalent circuit (the Cole model), estimate resistance at zero and infinite frequencies. Fitting of the experimental data to the model is accomplished by iterative, ...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/27/9/007
更新日期:2006-09-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/32/7/S10
更新日期:2011-07-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/aaaaa0
更新日期:2018-02-28 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/28/10/008
更新日期:2007-10-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/32/2/001
更新日期:2011-02-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/32/12/009
更新日期:2011-12-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章,评审
doi:10.1088/0967-3334/30/9/R01
更新日期:2009-09-01 00:00:00
abstract::Direct digital acquisition of images using a scanning laser ophthalmoscope (SLO) offers several advantages over the conventional fundus camera; in particular, the ability to produce tomographic images using a confocal aperture. This note describes measurements of the performance of an SLO. Spatial resolution, measured...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/15/3/010
更新日期:1994-08-01 00:00:00
abstract::Heart rate variability (HRV) is often analysed using short-term studies. Our objective was to compare two of them in a group of diabetic patients (reduced HRV) and in a control group. From the same 10 min surface electrocardiogram (ECG) two recordings were obtained. In one of them the whole signal was acquired through...
journal_title:Physiological measurement
pub_type: 临床试验,杂志文章
doi:10.1088/0967-3334/25/6/n01
更新日期:2004-12-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/abb141
更新日期:2020-10-06 00:00:00
abstract::This paper describes the design, construction, and testing of a multi-channel fetal electrocardiogram (fECG) signal generator based on LabVIEW. Special attention is paid to the fetal heart development in relation to the fetus' anatomy, physiology, and pathology. The non-invasive signal generator enables many parameter...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/37/2/238
更新日期:2016-02-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/ab3493
更新日期:2019-11-04 00:00:00
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journal_title:Physiological measurement
pub_type: 临床试验,杂志文章
doi:10.1088/0967-3334/32/4/008
更新日期:2011-04-01 00:00:00
abstract::In this study, we designed and tested a new algorithm, which we call the 'restricted parabola', to identify the optimum atrioventricular (AV) delay in patients with biventricular pacemakers. This algorithm automatically restricts the hemodynamic data used for curve fitting to the parabolic zone in order to avoid inadv...
journal_title:Physiological measurement
pub_type: 杂志文章,随机对照试验
doi:10.1088/0967-3334/36/9/1889
更新日期:2015-09-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/27/7/006
更新日期:2006-07-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/37/10/1785
更新日期:2016-10-01 00:00:00
abstract::Extension of the frequency range of electrical impedance myography (EIM) to 2 MHz discloses a major rise in the reactance of muscle above 3-500 kHz, together with a slow decrease in the resistance consonant with the Kramers-Kronig relations. This 'upturn' phenomenon is found when the distant current electrode configur...
journal_title:Physiological measurement
pub_type: 临床试验,杂志文章
doi:10.1088/0967-3334/29/6/S29
更新日期:2008-06-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/35/1/31
更新日期:2014-01-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/36/2/231
更新日期:2015-02-01 00:00:00
abstract::The purpose of this study was to determine the validity and reliability of a timed 5 km cycle ergometer ride to predict maximum oxygen uptake (VO2max). Fifty-two healthy volunteers had their VO2max determined during a maximal treadmill run. They also performed a timed 5 km cycle ergometer ride. The resistance setting ...
journal_title:Physiological measurement
pub_type: 临床试验,杂志文章,随机对照试验
doi:10.1088/0967-3334/17/4/009
更新日期:1996-11-01 00:00:00
abstract::This study was done to introduce new parameters derived by time frequency analysis of heart rate variability data. Four simulation experiments were carried out to compare the short-time Fourier transform (STFT) analysis method to the traditional overall spectral analysis method. Sinusoidal signals were generated with ...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/21/2/303
更新日期:2000-05-01 00:00:00
abstract::In the clinical environment the reliable interpretation of EIT images depends on the quality of the data. In the electrically noisy hospital environment the system performance needs to be assessed for each clinical investigation. From the model of noise presented, a figure of merit for comparisons of system performanc...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/17/4a/006
更新日期:1996-11-01 00:00:00
abstract::There has been a surge of interest in using electrical impedance tomography (EIT) for monitoring regional lung ventilation, however, EIT is an ill-conditioned problem, and errors/noise in the boundary voltages can have an undesirable effect on the quality of the final image. Most EIT systems in clinical usage use seri...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/34/6/659
更新日期:2013-06-01 00:00:00
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journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/37/1/100
更新日期:2016-01-01 00:00:00
abstract::The assessment and diagnosis of lower limb peripheral arterial occlusive disease (PAOD) is important since it can lead progressively to disabling claudication, ischaemic rest pain and gangrene. Historically, the first assessment has been palpation of the peripheral pulse since it can become damped, delayed and diminis...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/26/5/018
更新日期:2005-10-01 00:00:00
abstract::Current methods for analysing foetal heart rate (FHR) patterns have yet to meet their full potential in the recognition of hypoxia in the foetus. Following the recent suggestion that fractal analysis can be applied to FHR recordings, the current paper describes a method for distinguishing two simultaneous fractal dime...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/14/3/009
更新日期:1993-08-01 00:00:00