Abstract:
:In magnetic resonance electrical impedance tomography (MREIT) we inject currents through electrodes placed on the surface of a subject and try to reconstruct cross-sectional resistivity (or conductivity) images using internal magnetic flux density as well as boundary voltage measurements. In this paper we present a static resistivity image of a cubic saline phantom (50 x 50 x 50 mm3) containing a cylindrical sausage object with an average resistivity value of 123.7 ohms cm. Our current MREIT system is based on an experimental 0.3 T MRI scanner and a current injection apparatus. We captured MR phase images of the phantom while injecting currents of 28 mA through two pairs of surface electrodes. We computed current density images from magnetic flux density images that are proportional to the MR phase images. From the current density images and boundary voltage data we reconstructed a cross-sectional resistivity image within a central region of 38.5 x 38.5 mm2 at the middle of the phantom using the J-substitution algorithm. The spatial resolution of the reconstructed image was 64 x 64 and the reconstructed average resistivity of the sausage was 117.7 ohms cm. Even though the error in the reconstructed average resistivity value was small, the relative L2-error of the reconstructed image was 25.5% due to the noise in measured MR phase images. We expect improvements in the accuracy by utilizing an MRI scanner with higher SNR and increasing the size of voxels scarifying the spatial resolution.
journal_name
Physiol Measjournal_title
Physiological measurementauthors
Lee BI,Oh SH,Woo EJ,Lee SY,Cho MH,Kwon O,Seo JK,Baek WSdoi
10.1088/0967-3334/24/2/367subject
Has Abstractpub_date
2003-05-01 00:00:00pages
579-89issue
2eissn
0967-3334issn
1361-6579journal_volume
24pub_type
杂志文章abstract:OBJECTIVE:The Actiwatch 2 (AW2) is a wrist-worn accelerometer typically used to measure sleep. Although it can measure physical activity, there is limited evidence supporting its validity. We assessed the validity and reliability of the AW2 to measure sedentary behavior and physical activity (light, moderate, vigorous ...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/aba80f
更新日期:2020-09-04 00:00:00
abstract:BACKGROUND:Uterine activity monitoring is an essential part of managing the progress of pregnancy and labor. Although intrauterine pressure (IUP) is the only reliable method of estimating uterine mechanical activity, it is highly invasive. Since there is a direct relationship between the electrical and mechanical activ...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/ab37db
更新日期:2019-09-03 00:00:00
abstract:UNLABELLED:The study created an 'ex vivo' model to test different algorithms for measurements of mucosal haemoglobin saturation with visible light spectrophotometry (VLS). The model allowed comparison between algorithms, but it also allowed comparison with co-oximetry using a 'gold standard' method. This has not been d...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/37/9/1624
更新日期:2016-09-01 00:00:00
abstract::The effect of composition on the dielectric properties of hydrogels for biomedical applications is experimentally investigated. The hydrogels, containing hydroxyethylcellulose (HEC), are characterized by means of the impedance spectroscopy technique. The real and imaginary parts of the electrical impedance of the hydr...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/31/10/S02
更新日期:2010-10-01 00:00:00
abstract::Temporal variability of parameters which describe dynamic cerebral autoregulation (CA), usually quantified by the short-term relationship between arterial blood pressure (BP) and cerebral blood flow velocity (CBFV), could result from continuous adjustments in physiological regulatory mechanisms or could be the result ...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/29/4/006
更新日期:2008-04-01 00:00:00
abstract::This paper introduces a new clinical distortion index able to measure the decrease in diagnostic content in compressed echocardiograms. It is calculated using cardiologists' answers to a clinical testbed composed of two types of tests: one blind and the other semi-blind. This index may be used to compare clinical perf...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/30/5/001
更新日期:2009-05-01 00:00:00
abstract::We aim to investigate whether phase shift between respiratory oscillations in cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP) is associated with changes in cerebral autoregulation (CA) or reflects the mechano-elastic properties of the cerebrovascular bed. The relationships between respiratory pha...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/38/2/310
更新日期:2017-02-01 00:00:00
abstract:OBJECTIVE:Arterial CO2 (PaCO2) has a strong effect on cerebral blood flow (CBF), but its influence on CBF regulatory mechanisms and circulatory systemic variables has not been fully described over the entire physiological range of PaCO2. APPROACH:CBF velocity (CBFV, transcranial Doppler), blood pressure (BP, Finometer...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/aac76b
更新日期:2018-06-19 00:00:00
abstract::We investigated five different methods which can be applied to quantitatively construct functional tomograms of the lungs. The focus was on the sensitivity of functional tomograms to errors in acquired data. To quantify this sensitivity, theoretical, error-free data sets of well-known properties were artificially gene...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/31/8/S06
更新日期:2010-08-01 00:00:00
abstract::Patients with claudication have an inadequate haemodynamic response to exercise. Blood flow response will not only have a magnitude, but also a rate of change. There is scope for investigating these parameters, as manipulation of the factors which control them may benefit work to improve the treatment for claudication...
journal_title:Physiological measurement
pub_type: 临床试验,杂志文章
doi:10.1088/0967-3334/26/6/002
更新日期:2005-12-01 00:00:00
abstract::Easily applicable and inexpensive water-specific techniques to evaluate local oedema, swollen tissue problems and fluid retention in humans are not available. In the present investigation a recently constructed non-invasive device for a local measurement of changes in tissue water in human skin and subcutaneous fat (S...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/25/2/004
更新日期:2004-04-01 00:00:00
abstract::EPR oximetry is a promising, relatively non-invasive method for monitoring the partial pressure of oxygen in tissue (PtO2) that has proved useful in following changes under various physiologic and pathophysiologic conditions. Optimal utilization of the method will be facilitated by systematic comparisons with other av...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/25/6/007
更新日期:2004-12-01 00:00:00
abstract::The postural stability of 30 normal subjects in the age range 15 to 64 years was measured on five separate occasions, using the sway magnetometry technique, to determine the day-to-day repeatability of this measurement technique. On each occasion the pathlength and area enclosed by movement of the hips in a horizontal...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/19/2/003
更新日期:1998-05-01 00:00:00
abstract::This paper describes an open loop feedback intelligent system for neonatal intensive care management. The system provides a tool enabling the user to make the final decision to accept or reject the advice given. The system collects 18 parameters from the bedside monitor and ventilator using a Medical Information Bus (...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/26/4/019
更新日期:2005-08-01 00:00:00
abstract::This observational study investigated digital auscultation for the purpose of assessing the clinical feasibility of monitoring vascular sounds in pregnancy. The study was performed at the Regional Hospital Viborg, Denmark, and included 29 pregnant women, 10 non-pregnant women and 10 male participants. Digital ausculta...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/37/7/1163
更新日期:2016-07-01 00:00:00
abstract:OBJECTIVE:Physical activity has been shown to impact future health outcomes in adults, but little is known about the long-term impact of physical activity in toddlers. Accurately measuring the specific types and amounts of physical activity in toddlers will help us to understand, predict, and better affect their future...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/ab6ebb
更新日期:2020-03-06 00:00:00
abstract::Several factors affect the viability of biosensor design. A computer-based model is being developed to enable the sources and effect of noise and variability within the sensor to be analysed. The work now presented details the modelling of the biochemical aspect of the biosensor model-the immunoassay. The equilibrium ...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/22/3/318
更新日期:2001-08-01 00:00:00
abstract::The ambulatory arterial stiffness index (AASI) is claimed to be a new estimator for arterial rigidity. It was recently defined as one minus the slope of the linear regression of systolic to diastolic ambulatory pressure during 24 h. Although several reports testify its clinical relevance, the explanation of how this n...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/31/7/012
更新日期:2010-07-01 00:00:00
abstract::This paper discusses some important issues for the design of electrical impedance measurement systems intended for body fluid shift monitoring, in particular during dialysis treatments. We have studied two common signal generation systems: digital synthesis and carrier recovery. We have found that in prolonged measure...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/16/4/003
更新日期:1995-11-01 00:00:00
abstract:OBJECTIVE:U-shaped patterns, characteristic periods of time observed in tachograms, are a specific subgroup among very low frequency components characterized by relatively short periods of smooth accelerations followed by decelerations of heart rhythm. In this study, we characterize this phenomenon and its effect on he...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/ab9376
更新日期:2020-07-02 00:00:00
abstract::Polysomnography (PSG) has been extensively studied for sleep staging, where sleep stages are usually classified as wake, rapid-eye-movement (REM) sleep, or non-REM (NREM) sleep (including light and deep sleep). Respiratory information has been proven to correlate with autonomic nervous activity that is related to slee...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/35/12/2529
更新日期:2014-12-01 00:00:00
abstract:BACKGROUND AND OBJECTIVE:Walking is a complex human behavior, usually performed in a dynamic environment. Gait parameters are thought to reflect this complexity. Re-Step™ is a therapy system in the form of a computerized shoe, originally developed for the training and rehabilitation of individuals with brain damage. Th...
journal_title:Physiological measurement
pub_type: 临床试验,杂志文章
doi:10.1088/1361-6579/aab659
更新日期:2018-04-26 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::The recently-introduced technique of detrended fluctuation analysis (DFA) for heart-rate variability appears to yield improved prognostic power in cardiovascular disease through calculation of the fractal scaling exponent alpha. However, the physiological meaning of alpha remains unclear. In DFA, the signal is segment...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/23/2/314
更新日期:2002-05-01 00:00:00
abstract::Electrical impedance tomography (EIT) is a recent imaging technique based on electrical impedance, offering the possibility of measuring pulmonary perfusion. In the present study the influence of several pulmonary haemodynamical parameters on the EIT signal were investigated. First, the influence on the systolic wave ...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/19/2/013
更新日期:1998-05-01 00:00:00
abstract::We present an adaptive algorithm for solving the inverse problem in electrical impedance tomography. To strike a balance between the accuracy of the reconstructed images and the computational efficiency of the forward and inverse solvers, we propose to combine an adaptive mesh refinement technique with the adaptive Ka...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/35/6/1111
更新日期:2014-06-01 00:00:00
abstract:OBJECTIVE:It is accepted that changes in the peripheral pulse waveform characteristics occur with ageing. Pulse risetime is one important feature which has clinical value. However, it is unclear how it varies across the full age spectrum from child to senior and for different peripheral measurement sites. The objective...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/ab9b67
更新日期:2020-08-11 00:00:00
abstract::A gamma fit facilitates smoothing and extrapolation of distorted tracer-dilution curves in blood flow studies. Theoretically based empirical estimators were developed as simple alternatives to direct regression approaches from simulated gamma distributions with a wide range of shape asymmetry. Key curve features of pe...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/0967-3334/22/4/401
更新日期:2001-11-01 00:00:00
abstract:OBJECTIVE:To quantify the presence of cardiorespiratory interaction in a group of 41 healthy subjects performing a subset of the Ewing test battery. APPROACH:We measure the empirical distribution of the cardiorespiratory coupling time (RI), defined as the time from inspiration onset to R peaks in the ECG. The study pr...
journal_title:Physiological measurement
pub_type: 杂志文章
doi:10.1088/1361-6579/aa9693
更新日期:2017-11-30 00:00:00
abstract::Obesity is a major health issue in both developed and developing countries. The balance between energy intake and exercise is important, and measurements of both energy intake and energy expenditure are required. Many studies have attempted to monitor energy intake via wearable technology, but no standard methods have...
journal_title:Physiological measurement
pub_type: 杂志文章,评审
doi:10.1088/1361-6579/ab3827
更新日期:2019-09-03 00:00:00