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Freeston, I.L.; Tozer, R.C.
Impedance imaging using induced currents
Journal Physiological Measurement
16
Suppl. 3A
AUG
1995
A257-A266
IL Freeston
Univ Sheffield
Dept Electr & Elect Engn
Mappin St
Sheffield S1 3JD
S Yorkshire, England
TOMOGRAPHY
The principal features of an electrical impedance tomography system using induced currents are described. Images of the distribution of conductivity in a two-dimensional phantom are obtained using an algorithm based on a sensitivity matrix. Results are also presented which demonstrate the separation of conductivity and permittivity images from measurements of the complex peripheral voltage, the formation of unreferenced permittivity images, and the use of capacitively coupled electrodes in a measuring system without direct electrical contact. |
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Author(s):
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Abstract: |
Freeston, I.L.; Tozer, R.C.
Impedance imaging using induced currents
Journal Physiological Measurement
16
Suppl. 3A
AUG
1995
A257-A266
IL Freeston
Univ Sheffield
Dept Electr & Elect Engn
Mappin St
Sheffield S1 3JD
S Yorkshire, England
0967-3334
TOMOGRAPHY
The principal features of an electrical impedance tomography system using induced currents are described. Images of the distribution of conductivity in a two- dimensional phantom are obtained using an algorithm based on a sensitivity matrix. Results are also presented which demonstrate the separation of conductivity and permittivity images from measurements of the complex peripheral voltage, the formation of unreferenced permittivity images, and the use of capacitively coupled electrodes in a measuring system without direct electrical contact. |
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Fisch, B.J.; Spiegel, D.M.
Assessment of excess fluid distribution in chronic hemodialysis patients using bioimpedance spectroscopy
Kidney International
49
4
APR
1996
1105-1109
DM Spiegel
Univ Colorado
Hlth Sci Ctr
Box C-281
Denver, CO 80262 USA
0085-2538
TOTAL-BODY WATER; FAT-FREE BODY; HYDRATION; IMPEDANCE
Sodium and water homeostasis is abnormal in hemodialysis (HD) patients, however, the distribution of the excess fluid (extracellular vs. intracellular) has not been fully characterized. We studied the distribution of fluid using bioimpedance spectroscopy to determine if HD patients have an excess of fluid in any specific compartment relative to controls. Dual-energy x-ray absorptiometry was used to measure lean body mass and bone mineral content. The resistive index (RI) for extracellular water volume (RI(ECW)), was significantly increased in patients pre-HD when corrected for bone mineral content (RI(ECW):BMC) (pre- HD, 19.0 +/- 3.3; controls, 15.8 +/- 1.7 cm(2)-ohms(-1)-kg(- 1); P < 0.01). This value decreased to the control range following HD (15.2 +/- 2.5 cm(2)-ohms(-1)-kg(-1)). The intracellular water volume to bone mineral content (RI(ICW): BMC) was not different between controls and HD patients. These data suggest that hemodialysis patients carry their excess fluid volume primarily in the extracellular compartment and that bioimpedance spectroscopy coupled with a stable measure of lean tissue such as bone mineral content can determine the degree of relative excess hydration. |
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Fisker, S.; Vahl, N.; Jorgensen, J.O.L.; Christiansen, J.S.; Orskov, H.
Abdominal fat determines growth hormone-binding protein levels in healthy
non-obese adults
Journal Journal of Clinical Endocrinology and Metabolism
82
1
JAN
1997
123-128
S Fisker
Aarhus Kommune Hosp
Dept Endocrinol & Diabet
Norrebrogade 44
DK-8000 Aarhus C, Denmark
0021-972X
DEPENDENT DIABETES-MELLITUS; RECOMBINANT HUMAN GH; ABNORMAL BODY-COMPOSITION; IDIOPATHIC SHORT STATURE; LARON-TYPE DWARFISM; FACTOR-I; ANOREXIA-NERVOSA; DEFICIENT ADULTS; IMMUNOFUNCTIONAL ASSAY; (GH)-BINDING PROTEIN
The circulating high affinity GH-binding protein (GHBP), which derives from the extracellular domain of the hepatic GH receptor, correlates inversely to GH levels and directly to body mass index (BMI) in healthy adults. As GH secretion and adiposity are also interrelated, we tested the hypothesis that body composition, more than GH, determines GHBP levels in healthy adults. Forty-two healthy adults [21 females and 21 males; mean age, 39.4 yr range, 27-59 yr); mean BMI, 23.9 kg/m(2) (range, 18.9-34.7 kg/m(2))], underwent anthropometric measurements (BMI, W/H ratio, computed tomography scan, dual energy x-ray absortiometry (DEXA) scan, and bioimpedance) in addition to two GH stimulation tests (arginine and clonidine) and a 24-h GH profile. By simple linear regression, serum GHBP correlated positively to several indices of adiposity: intraabdominal fat (r = 0.537; P = 0.001), sc abdominal fat (r = 0.680; P < 0.001), BMI = 0.483; P = 0.001), W/H ratio (r = 0.452; P = 0.003), total body fat (DEXA scanning; r = 0.503; P = 0.002), and body fat (bioimpedance; r = 0.354; P = 0.023). Lean body mass estimated by DEXA scan was negatively associated with GHBP (r = 0.541; P < 0.001). GHBP was inversely proportional to arginine-stimulated GH release (r = -0.346; P = 0.027) and negatively associated with several measures of spontaneous GH release as estimated by deconvolution analysis (GH mass, GH production rate, and mean GH; r = -0.371; P = 0.017, r = -0.393; P = 0.011, and r = -0.343; P = 0.028, respectively)). With multiple linear regression analyses, indices of adiposity were significant determinants of GHBP levels, whereas GH status did not contribute independently to the prediction of GHBP. Neither insulin-like growth factor I nor fasting insulin levels correlated to GHBP levels. In conclusion, GHBP levels in normal adults seem to be determined by abdominal fat mass rather than GH secretion. |
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Frerichs, I.; Hahn, G.; Hellige, G.
Gravity-dependent phenomena in lung ventilation determined by functional EIT
Journal Physiological Measurement
17
Suppl. 4A
NOV
1996
A149-A157
I Frerichs
Univ Gottingen
Ctr Anaestheisol & Emergency
& Intens Care Med
Dept Anaesthesiol Res
Tl 195
D-37075 Gottingen, Germany
0967-3334
Tomography
Gravity exerts an effect on the distribution of intrapulmonary ventilation. A study on the detection of gravity-dependent inhomogeneity of ventilation by a functional EIT technique is presented. The study was performed on five human subjects, whose ventilation distribution was modified by changes in body position. The subjects were studied during spontaneous tidal breathing. The qualitative and quantitative analysis of the functional EIT images revealed that the ventilation is higher in the dependent lung regions when compared with the non-dependent ones. These EIT findings correspond to current knowledge of the physiological behaviour of the lungs as derived from the radioactive-gas methods and raise the possibility of applying the less complicated functional EIT in future studies on ventilation distribution in the lungs. This may be of major interest in the monitoring of intensive care patients with severe pulmonary disorders. |
