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Gabriel, C.; Gabriel, S.; Corthout, E.
The dielectric properties of biological tissues .1. Literature survey
Journal Physics in Medicine and Biology
41
11
NOV
1996
2231-2249
C Gabriel
Univ London Kings Coll
Dept Phys
London WC2R 2LS, England
0031-9155
FLUID-SATURATED BONE; ELECTRICAL-PROPERTIES; SKELETAL-MUSCLE; MICROWAVE-FREQUENCIES; LOW RADIOFREQUENCIES; POSTMORTEM CHANGES; ANIMAL-TISSUES; BRAIN-TISSUE; INVIVO; INVITRO.
The dielectric properties of tissues have been extracted from the literature of the past Ave decades and presented in a graphical format. The purpose is to assess the current state of knowledge, expose the gaps there are and provide a basis for the evaluation and analysis of corresponding data from an on-going measurement programme. |
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Gabriel, S.; Lau, R.W.; Gabriel, C.
The dielectric properties of biological tissues .2. Measurements in the frequency range 10 Hz to 20 GHz
Journal Physics in Medicine and Biology
41
11
NOV
1996
2251-2269
S Gabriel
Univ London Imperial
Coll Sci Technol & Med
Dept Chem
London SW7 2AY, England
0031-9155
Three experimental techniques based on automatic swept- frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz. The technique used in conjunction with the impedance analyser is described. Results are given for a number of human and animal tissues, at body temperature, across the frequency range, demonstrating that good agreement was achieved between measurements using the three pieces of equipment. Moreover, the measured values fall well within the body of corresponding literature data. |
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Gabriel, S.; Lau, R.W.; Gabriel, C.
The dielectric properties of biological tissues .3.
Parametric models for the dielectric spectrum of tissues
Journal Physics in Medicine and Biology
41
11
NOV
1996
2271-2293
S Gabriel
Univ London Imperial
Coll Sci Technol & Med
Dept Chem
London SW7 2AY, England
0031-9155
PERMITTIVITY; WATER; GHZ
A parametric model was developed to describe the variation of dielectric properties of tissues as a function of frequency. The experimental spectrum from 10 Hz to 100 GHz was modelled with four dispersion regions. The development of the model was based on recently acquired data, complemented by data surveyed from the literature. The purpose is to enable the prediction of dielectric data that are in line with those contained in the vast body of literature on the subject. The analysis was carried out on a Microsoft Excel spreadsheet. Parameters are given for 17 tissue types. |
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Gasperino, J.A.; Wang, J.; Pierson, R.N.; Heymsfield, S.B.
Age-related changes in musculoskeletal mass between black and white women
Journal Metabolism - Clinical and Experimental
44
1
JAN
1995
30-34
SB Heymsfield
St Lukes Roosevelt Hosp
Obes Res Ctr
Amsterdam Ave W 114TH St
10TH Floor
Womans Hosp R
New York, NY 10025 USA
0026-0495
HORMONE-BINDING GLOBULIN; TRABECULAR BONE-DENSITY; BODY- COMPOSITION; ANDROGENS; CARBOHYDRATE; OBESITY; MUSCLE; CELLS.
Earlier studies from our laboratory indicated that matched black and white women differ significantly in total body potassium (TBK), total body bone density (TBD), and total body bone mineral (TBBM). The aim of this investigation was to examine absolute levels and the kinetics of age-related changes in TBK, TBD, TBBM, and percent body fat in a cross-sectional cohort of 34 matched pairs (age +/- 4 years, weight +/- 2 kg, and height +/- 4 cm) of black and white healthy non obese women. Black and white women had a similar percentage of body weight as fat, although adipose tissue distribution tie, waist to hip circumference ratio [WHR]) differed significantly (P < .0007) between the two groups (WHR, mean +/- SD: black, 0.837 +/- 0.062; white, 0.788 +/- 0.043). TBBM and TBD were significantly (P < .0001) higher in young black women, and ethnic differences in total bone mineral mass persisted at all ages. TBK (P = 0.0482) and appendicular skeletal muscle mass (P < .0001) were higher in young black women; however, by ages 60 to 70 years, the two groups had similar TBK. Both groups of women lost musculoskeletal mass tie, TBK and TBBM) and gained fat mass at similar rates. The results of this study suggest that black women have a greater appendicular muscle and skeletal mass, as well as upper-body fat distribution, than white women. These differences are independent of body weight, height, or percent fat, and the ethnic skeletal differences persist throughout the adult life span. The higher appendicular muscle mass, skeletal mass, and upper-body fat distribution suggest that black women may have greater androgenic activity than white women. Copyright (C) 1995 by W.B. Saunders Company |
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Geddes LA
Historical evolution of circuit models for the electrode-electrolyte interface.
English
Review
Ann Biomed Eng 1997 JAN-FEB;25(1):1-14
Geddes LA, Hillenbrand Biomed Engn Ctr, AA Potter Bldg
204, W Lafayette,IN 47907 USA
Electrodes are widely used to measure bioelectric events and to stimulate excitable tissues. In one form or another, electrodes have been around for nearly two centuries; yet our ability to predict their properties is extremely Limited, despite considerable research, especially during the last century. This paper chronicles the accumulation of knowledge about the electrode-electrolyte interface as a circuit element. Our understanding of this interface starts with the Helmholtz double layer of charge and progresses through the Warburg and Fricke low-current-density models, which demonstrated that the resistive and capacitive components are polarization elements, the values of which depend on frequency. The discovery by Schwan, showing that the components of the Warburg-Fricke model are current-density dependent, is recounted, along with the discovery of the rectifying properties of the electrode-electrolyte interface and how it was put to practical use. The very high current-density operation of the interface is discussed in terms of gas evolution, arcing, and shock-wave production. Finally the evolution of recording electrodes is traced. Because electrodes can be operated over a very wide range of current density, it is unlikely that a single model can be created for the electrode-electrolyte interface, although over a restricted current- density range such a model may be possible. |
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Gencer, N.G.; Ider, Y.Z.; Williamson, S.J.
Electrical impedance tomography: Induced-current imaging achieved with a multiple coil system
Journal IEEE Transactions on Biomedical Engineering
43
2
FEB
1996
139-149
NG Gencer
NYU
Dept Phys, Meyer Hall Phys
2 Washington Pl
New York, NY 10003 USA
0018-9294
An experimental study of induced-current electrical impedance tomography verifies that image quality. Is enhanced by employing six rather than three induction coils by increasing the number of independent measurements. However, with an increasing number of coils, the inverse problem becomes more sensitive to measurement noise. Using 16 electrodes to measure surface voltages, it Is possible to collect 6 x 15 = 90 independent measurements. For comparison purposes, images of two dimensional conductivity perturbations are reconstructed by using the data for three and six coils with the truncated pseudoinverse algorithm. By searching for the optimal truncation index that minimizes the noise error plus the resolution error, the signal-to-noise ratio of the data acquisition system was established as 58 db, Images obtained with this six-coil system reveal the sizes and locations of the conductivity perturbations, This system also provides images within the central region of the object space, a capability not achieved in previous experimental studies using only three circular coils. Nevertheless, the three-coil system can identify the conductivity perturbations near the periphery. However, it displays shifts in the locations and spread in the sizes of perturbations near the center of the object. |
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Gersing, E.; Kruger, W.; Osypka, M.; Vaupel, P.
Problems involved in temperature measurements using EIT
Journal Physiological Measurement
16
Suppl. 3A
AUG
1995
A153-A160
E Gersing
Univ Gottingen
Zentrum Physiol & Pathophysiol
Humboldtallee 23
Gottingen, Germany
0967-3334
In cancer therapy, hyperthermic treatment by microwaves requires a non-invasive and reliable method for measuring the temperature distribution inside the body. EIT seems to be able to evaluate the temperature-dependent tissue impedance for delivering the temperature profile in a cross-section of the body. Assuming a temperature coefficient of the resistivity of an electrolyte of about -2% degrees C-1 and temperature measurement to an accuracy of 0.5 degrees C, the error in impedance measurement must be lower than 1%. Irrespective of the accuracy of the tomographic measuring system itself, a problem arises from the fact that the fluid content in the tissue as well as the fluid distribution between the extracellular and the intracellular compartment change with temperature. Measurements of the impedance spectra of skeletal muscle and tumours of rats during hyperthermic treatment deliver very different temperature coefficients of the resistivity from -1.3% degrees C-1 to -3% degrees C-1, thus questioning the feasibility of the EIT as a temperature measuring method. However, changes in the tissue caused by hyperthermia (e.g., fluid shifts, development of oedema and membrane disintegration) can be detected. |
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Gersing, E.; Kruger, W.; Osypka, M.; Vaupel, P.
Problems involved in temperature measurements using EIT
Journal Physiological Measurement
16
Suppl. 3A
AUG
1995
A153-A160
E Gersing
Univ Gottingen
Zentrum Physiol & Pathophysiol
Humboldtallee 23
Gottingen, Germany
0967-3334
In cancer therapy, hyperthermic treatment by microwaves requires a non-invasive and reliable method for measuring the temperature distribution inside the body. EIT seems to be able to evaluate the temperature-dependent tissue impedance for delivering the temperature profile in a cross-section of the body. Assuming a temperature coefficient of the resistivity of an electrolyte of about -2% degrees C-1 and temperature measurement to an accuracy of 0.5 degrees C, the error in impedance measurement must be lower than 1%. Irrespective of the accuracy of the tomographic measuring system itself, a problem arises from the fact that the fluid content in the tissue as well as the fluid distribution between the extracellular and the intracellular compartment change with temperature. Measurements of the impedance spectra of skeletal muscle and tumours of rats during hyperthermic treatment deliver very different temperature coefficients of the resistivity from -1.3% degrees C-1 to -3% degrees C-1, thus questioning the feasibility of the EIT as a temperature measuring method. However, changes in the tissue caused by hyperthermia (e.g., fluid shifts, development of oedema and membrane disintegration) can be detected. |
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Gersing E; Hofmann B; Osypka M
Influence of changing peripheral geometry on electrical impedance tomography measurements.
English
Article
Med Biol Eng Comput 1996 SEP;34(5):359-361
Gersing E, Univ Gottingen, Inst Physiol & Pathophysiol, Humboldt Allee 23, D 37073 Gottingen, GERMANY |
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Giner, M.; Laviano, A.; Meguid, M.M.; Gleason, J.R.
In 1995 a correlation between malnutrition and poor outcome in critically ill patients still exists
Nutrition
12
1
JAN
1996
23-29
MM Meguid
SUNY Hlth Sci Ctr
Univ Hosp
Dept Surg
Surg Metab & Nutr Lab
750 E Adams St
Syracuse, NY 13210 USA
0899-9007
hospital-related malnutrition; serum albumin; weight/height ratio; intensive care unit (ICU); Therapeutic Intervention Scoring System (TISS); outcome,BIOELECTRICAL IMPEDANCE ANALYSIS; GENERAL SURGICAL PATIENTS; NUTRITIONAL-STATUS; GASTROINTESTINAL SURGERY; OPERATIVE MORBIDITY; MEDICAL PATIENTS; BODY-COMPOSITION; PROTEIN STATUS; FOOD-INTAKE; UNDERNUTRITION
After more than two decades of nutritional awareness, we designed a prospective study to determine whether malnutrition is still a significant issue in hospitalized patients. Patients admitted to an intensive care unit (ICU) were divided into well-nourished and malnourished groups, according to their nutritional status as assessed by serum albumin level and weight/height ratio. Severity of illness, as assessed by the Therapeutic Intervention Scoring System (TISS), was used to further stratify the study population. All patients were followed clinically until discharge or death and their outcome recorded. Of 129 patients studied, 43% were malnourished. Length of hospital stay (p = n.s.), incidence of complications (p < 0.01), and number of patients not discharged from hospital (p < 0.05) were greater in the malnourished patients than in the well-nourished. In patients with less severe degrees of illness, the existence of malnutrition led to a worse outcome than in sicker patients. To further assess the clinical setting in which hospital-related malnutrition develops or is
exacerbated, postoperative patients admitted to the ICU (n = 66) were also studied in a nutritional survey; the results of this survey indicate that: (a) the incidence of malnutrition in the surgical population is similar to that in the whole study population, and (b) hospital-related malnutrition in surgical patients mainly develops during their preoperative stay in general wards. Whereas our conclusion that patients' outcome is adversely affected by a poor nutritional status is not new or startling, malnutrition continues to be a persistent problem in hospitalized patients, which can be readily identified using simple and easily available indices and, furthermore, readily treated. |
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Gonzalez, J.; Morrissey, T.; Byrne, T.; Rizzo, R.; Wilmore, D.
Bioelectric impedance detects fluid retention in patients undergoing cardiopulmonary bypass
Journal Journal of Thoracic and Cardiovascular Surgery
110
1
JUL
1995
111-118
D Wilmore
Brigham & Womens Hosp
Thorn Res Bldg
14TH Floor
20 Shattuck St
Boston, MA 02115 USA
0022-5223
TOTAL-BODY WATER; RELEASE
Excessive fluid accumulation is associated with increased morbidity and prolonged convalescence after cardiopulmonary bypass. However, water fluctuations are difficult to assess solely on the basis of changes in body weight and fluid balance. Bioelectric impedance analysis is a simple, rapid, noninvasive bedside technique that measures the resistance of the body to a weak alternating current (50 kHz). The change in resistance is inversely proportional to the change in total body water, To investigate the relationship between body weight, fluid balance, and resistance, 18 patients who had cardiopulmonary bypass (9 men, 9 women, aged 61 +/- 3 years, weighing 80 +/- 4 kg, with ejection fraction 54% +/- 3% and bypass time 113 +/- 8 minutes [mean plus or minus standard error of the mean]) were followed up for 7 postoperative days. Body weight, fluid balance, and whole body and regional resistance were determined at 24- hour intervals. In the immediate postoperative period, fluid retention was accurately detected by simultaneous measurements of weight gain and decreased resistance (p < 0.001). Both measurements detected the initiation of diuresis by postoperative day 2 (p < 0.01). Whole body resistance returned to baseline values by day 7 (p 0.05), and body weight returned to baseline on day 4 (p 0.05). Change in weight and change in whole body resistance were highly correlated with cumulative fluid balance (r = 0.84, p < 0.001, and r = -0.81,p < 0.001, respectively), and these two measures were also related to each other throughout the study (r = -0.89, p < 0.001). The initial change in resistance was the best measurement associated with postoperative outcome (p less than or equal to 0.01). The data suggest that the measurement of electric resistance across the body can accurately detect acute changes in total body water and in fluid redistribution through the body. However, determining the relative day-to- day change in whole body resistance seems more appropriate than calculating absolute fluid changes over time. Bioelectric impedance offers a simple, rapid, noninvasive method to monitor serial changes in total body water, This technique can be useful in situations in which rapid alterations in water compartments occur, and it may be useful in predicting outcome after cardiopulmonary bypass. |
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Gonzalez, J.; Morrissey, T.; Byrne, T.; Rizzo, R.; Wilmore, D.
Bioelectric impedance detects fluid retention in patients undergoing cardiopulmonary bypass
Journal of Thoracic and Cardiovascular Surgery
110
1
JUL
1995
111-118
D Wilmore
Brigham & Womens Hosp
Thorn Res Bldg
14TH Floor
20 Shattuck St
Boston, MA 02115 USA
0022-5223
TOTAL-BODY WATER; RELEASE
Excessive fluid accumulation is associated with increased morbidity and prolonged convalescence after cardiopulmonary bypass. However, water fluctuations are difficult to assess solely on the basis of changes in body weight and fluid balance. Bioelectric impedance analysis is a simple, rapid, noninvasive bedside technique that measures the resistance of the body to a weak alternating current (50 kHz). The change in resistance is inversely proportional to the change in total body water, To investigate the relationship between body weight, fluid balance, and resistance, 18 patients who had cardiopulmonary bypass (9 men, 9 women, aged 61 +/- 3 years, weighing 80 +/- 4 kg, with ejection fraction 54% +/- 3% and bypass time 113 +/- 8 minutes [mean plus or minus standard error of the mean]) were followed up for 7 postoperative days. Body weight, fluid balance, and whole body and regional resistance were determined at 24- hour intervals. In the immediate postoperative period, fluid retention was accurately detected by simultaneous measurements of weight gain and decreased resistance (p < 0.001). Both measurements detected the initiation of diuresis by postoperative day 2 (p < 0.01). Whole body resistance returned to baseline values by day 7 (p 0.05), and body weight returned to baseline on day 4 (p 0.05). Change in weight and change in whole body resistance were highly correlated with cumulative fluid balance (r = 0.84, p < 0.001, and r = -0.81,p < 0.001, respectively), and these two measures were also related to each other throughout the study (r = -0.89, p < 0.001). The initial change in resistance was the best measurement associated with postoperative outcome (p less than or equal to 0.01). The data suggest that the measurement of electric resistance across the body can accurately detect acute changes in total body water and in fluid redistribution through the body. However, determining the relative day-to- day change in whole body resistance seems more appropriate than calculating absolute fluid changes over time. Bioelectric impedance offers a simple, rapid, noninvasive method to monitor serial changes in total body water, This technique can be useful in situations in which rapid alterations in water compartments occur, and it may be useful in predicting outcome after cardiopulmonary bypass. |
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Goran, M.I.; Driscoll, P.; Johnson, R.; Nagy, T.R.; Hunter, G.
Cross-calibration of body-composition techniques against dual- energy X-ray absorptiometry in young children
American Journal of Clinical Nutrition
63
3
MAR
1996
299-305
MI Goran
Univ Alabama
Dept Nutr Sci
Energy Metab Res Unit
Birmingham, AL 35294 USA
0002-9165
skinfold-thickness measurements; dual-energy X-ray absorptiometry; bioelectrical resistance; obesity; body composition; fat mass; fat-free mass; lean mass SKINFOLD EQUATIONS; DENSITY; VALIDATION; IMPEDANCE; ADULTS; YOUTH; FAT
Using dual-energy X-ray absorptiometry (DXA) as a standard method for determining body composition in children, we evaluated the accuracy of skinfold-thickness measurements (with the Slaughter et al equations, which are based on triceps and calf skinfold-thickness measurements), bioelectrical resistance (BR; with the Kushner et al equations and age-specific hydration constants), and other clinical measurements (individual skinfold thicknesses and body mass index) for the assessment of body fat in children. We studied a heterogenous group of 49 boys and 49 girls, aged 6.6 +/- 1.4 y and weighing 24.1 +/- 5.9 kg. Fat mass estimated by DXA was significantly lower than fat mass measured by skinfold thickness, even though fat mass measurements by these two techniques were strongly related to each other. Fat mass estimated by DXA was also significantly lower than fat mass measured by BR, and the model R(2) and SEE were not as strong as for the skinfold- thickness technique. Fat mass estimated by DXA also correlated with other clinical indexes such as triceps skinfold thickness, body mass index, body weight, and subscapular skinfold thickness. In forward-regression analysis, subscapular skinfold thickness, body weight, triceps skinfold thickness, sex, and height(2)/resistance estimated the value for fat mass measured by DXA with a model R(2) Of 0.91 and an SEE of 0.94 kg fat mass. These studies suggest that existing techniques for assessing body fat in children may be inaccurate. We provide new anthropometric equations based on the use of DXA as a criterion that provide accurate and precise measures of body fat and fat-free mass in white children aged 4-9 y. This approach provides estimates of body fat standardized to a known laboratory standard of chemical analysis of carcasses. |
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Goran, M.I.; Nagy, T.R.
Effect of the pre-testing environment on measurement of metabolic rate in children
Journal International Journal of Obesity
20
1
JAN
1996
83-87
MI Goran
Univ Alabama
Dept Nutr Sci
Energy Metab Res Unit
Birmingham, AL 35294 USA
0307-0565
children; energy expenditure; physical activity; measurement biasBODY-COMPOSITION
OBJECTIVE: To examine two different protocols for measurement of metabolic rate (MR) in children.
DESIGN: MR was first measured under typical basal conditions employed in adults and then compared to an alternative protocol in which the measurements were performed in post-prandial state. Repeat measurements were performed for the post-prandial protocol.
SUBJECTS: The cross-over study was performed in 19 healthy children and the reliability data were provided from 169 observations in children. All children were 4-9 years of age.
MEASUREMENTS: basal MR was measured in the morning in the fasted state after children spent the night at The Clinical Research Center. Measurements were repeated 2 weeks later after children reported to the laboratory after consuming their normal breakfast at home (post-prandial). Body composition was measured using bioelectrical resistance.
RESULTS: MR was similar to 11% higher under post-prandial conditions (1165 +/- 151 kcal/day vs 1050 +/- 151 kcal/day; p < 0.001 by paired t-test). Respiratory quotient (RQ) was similar to 3% higher under post prandial conditions (0.94 +/- 0.03 vs 0.91 +/- 0.05; p < 0.001 by paired t-test). The correlation between MR and fat free mass was stronger when measurements were performed under post-prandial (r = 0.88; p < 0.001) vs basal conditions (r = 0.64; p < 0.005). The coefficient of variation for 169 repeat measurements using the post-prandial protocol averaged 5.4 +/- 4.1% for MR and 2.9 +/- 2.2% for RQ.
CONCLUSIONS: The stronger correlation between MR and fat free mass during post prandial measurements implies that the less stringent testing conditions improves compliance during measurement and provides the environment for reproducible measurements. We propose an alternative protocol for determination of post-prandial metabolic rate in children that is reliable, practical and can be potentially applied in a clinical setting. |
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Griffiths, H.
A Cole phantom for EIT
Journal Physiological Measurement
16
Suppl. 3A
AUG
1995
A29-A38
H Griffiths
Inserm
U281
151 Cours Albert Thomas
F-69424 Lyon 03, France
0967-3334
A phantom was designed for testing and comparing multifrequency EIT data collection systems. The phantom simulates a cylinder of homogeneous conductor with 16 drive and 16 receive electrodes interleaved. Combinations of resistors and capacitors were used to simulate the complex impedance, Z*, of a typical tissue in the frequency range 8- 2048 kHz obeying the Cole equation Z* = Z(infinity) + (Z(0) - Z(infinity))/[1 + (i f/f(c))((1- alpha))] where Z* is the complex impedance at frequency f, Z(0) and Z(infinity) are the limiting values of impedance at low and high frequencies, f(c) is the characteristic frequency and alpha is a constant. A practical phantom was then constructed on which four different sets of spectroscopic parameters could be selected: (i) alpha = 0.20, f(c) = 150 kHz, Z(0)/Z(infinity) = 3.31; (ii) alpha = 0, f(c) = 273 kHz, Z(0)/Z(infinity) = 2.64; (iii) alpha = 0, f(c) = 71.1 kHz, Z(0)/Z(infinity) = 1.36 and (iv) Z(0)/Z(infinity) = 1.00 with no dispersion. |
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Griffiths, H.; Tucker, M.G.; Sage, J.; Herrendenharker, W.G.
Title An electrical impedance tomography microscope
Journal Physiological Measurement
17
Suppl. 4A
NOV
1996
A15-A24
H Griffiths
Univ Wales Hosp
Dept Med Phys & Bioengn
Heath Pk
Cardiff CF4 4XW
S Glam, Wales
0967-3334
CLINICAL-APPLICATIONS
A circular array of 16 electrodes has been constructed for use as an electrical impedance tomography (EIT) microscope. The electrodes were made from 60 mu m diameter gold wires anchored to a printed circuit board. The internal diameter of the array was 0.9 mm giving a theoretical spatial resolution of about 100 mu m. For EIT imaging, the array was connected to an imaging system operating at 82 kHz. Static images of conducting and insulating filaments (copper wire and human hair) in saline solution were obtained as well as dynamic imaging sequences of glass microspheres migrating through the array. The interelectrode impedance was typically 5 k Omega and the transimpedances ranged from 14 to 210 Omega. |
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Griffiths, H.
Tissue spectroscopy with electrical impedance tomography: Computer simulations
Journal IEEE Transactions on Biomedical Engineering
42
9
SEP
1995
948-954
H Griffiths
Univ Wales Hosp
Dept Med Phys & Bioengn
Heath Pk
Cardiff CF4 4XW
S Glam, Wales
0018-9294
COMPLEX IMPEDANCE; SYSTEM
A method is proposed by which bioelectrical spectroscopy could be combined with electrical impedance tomography (EIT) to provide noninvasive characterization of tissue. Multifrequency (2-200 kHz) EIT measurements were simulated with a numerical model for a volume of porcine liver immersed in an electrolytic tank. From the reconstructed EIT images the tissue characterization method was then applied enabling a plot of complex resistivity to be drawn for any selected pixel in the image. Simulations were performed for a small volume of degraded tissue embedded in the normal tissue to examine its effect on the derived spectroscopic parameters, The method could have an application in transplant surgery for screening organs for tissue degradation. |
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Guggenbuhl, P.
Comparative determinations of rat body composition by chemical, near infrared reflectance and total body electrical conductivity analyses
Journal Methods and Findings in Experimental and Clinical Pharmacology
17
9
NOV
1995
621-627
P. Guggenbuhl
Soc Chim Roche
Dept Crna
BP 170
F-68305 Villejuif, France
0379-0355
rats; body lipid contents; body protein contents; chemical analyses; near infrared analyses; total body electrical conductivity analyses CIMATEROL; AGONIST; GROWTH; FAT; SPECTROSCOPY; PROTEIN; CARCASS; BIRDS
Rat carcass characteristics were determined by classical chemical analyses, near infrared reflectance (NIR) and total body electrical conductivity (TOBEC), with the aim to establish a rapid reliable and soft method for numerous body composition predictions. In order to get a wide range in rat carcass protein and fat contents, animals were fed ad libitum with a commercial diet supplemented with various doses of cimaterol, alpha beta(2)-adrenergic agonist having repartitioning effects. Samples analyzed by chemical methods allowed a suitable NIR calibration for protein and fat rat carcass contents. Comparison of chemical chemical and NIR predictions gave equal values for protein and fat determinations. A linear correlation (R = 0.974) could be defined between both parameters. Similarly the comparison
of rat var fat content determined with NIR and TOBEC also showed a linear correlation (R = 0.984). These correlations allowed to calculate rat protein content after TOBEC fat measurements, using the prediction equation established from the linear protein-fat correlation found after NIR analyses. Calculated and NIR measured protein content values had a correlation coefficient of 0.956. It was concluded that for the experimental conditions and the animal strain used, TOBEC analyses showed the best qualities to meet the fixed goals. TOBEC appeared as a suitable noninvasive method for body composition determinations. Furthermore, the technique enables repeated measurements in living animals for kinetic evaluation studies. |
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Gutin, B.; Litaker, M.; Islam, S.; Manos, T.; Smith, C.; Treiber, F.
Body-composition measurement in 9-11-y-old children by dual- energy X-ray absorptiometry, skinfold-thickness measurements, and bioimpedance analysis
American Journal of Clinical Nutrition
63
3
MAR
1996
287-292
B Gutin
Med Coll Georgia
Georgia Prevent Inst
HS1651
Augusta, GA 30912 USA
0002-9165
dual-energy X-ray absorptiometry; bioimpedance analysis; skinfold-thickness measurement; body composition; children MASS
We compared, in 9-11-y-old children (n = 43), three measures of body composition: dual-energy X-ray absorptiometry (DXA), skinfold thickness, and bioimpedance analysis (BIA). The intraclass correlation coefficient (ICC), Bland-Altman procedure, and Spearman rank correlation were used to determine test-retest reliabilities of the three methods and to compare methods. For DXA measurements, the rank correlation between fat-free soft tissue acid fat-free mass (FFM) was 0.99, indicating that bone mineral content did not provide independent information. Thus, subsequent analyses used the two-compartment model tie, fat mass and FFM) for all three techniques, focusing especially on ;I values for percentage of fat. The test-retest reliabilities for all methods were high (ICCs 0.994 and no significant differences between trials 1 and 2). The range of individual differences from I: trial 1 to trial 2 and Bland-Altman limits of agreement suggested that the reliability was greatest for DXA, followed by BIA and skinfold-thickness measurement. The percentage of fat values for the three methods were highly intercorrelated (all Spearman r values 0.83). However, there was a systematic tendency (P < 0.01) for DXA values (mean: 23.98) to be higher than those derived from skinfold- thickness measurements (mean: 21.05) and BIA (mean: 21.52). The variance in percentage of fat values for BIA was significantly smaller than that for the other two techniques. These findings, along with rather large limits of agreement derived from the Bland-Altman procedure, suggest that the methods should not be used interchangeably. |
