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differences were observed between groups. Table 1 Anthropometric data. Variables Groups Mean Age (years) Mass (kg) Height (m) BMI (kg/m 2 ) Mean 32 80.81 1.81 24.77 Paraplegic active SD 6.06 17.19 0.07 4.24 CI 26.4- 64,91- 1.74- 20.85- 37.6 96.71 1.86 28.69 Mean 37.73 77.43 1.74 25.58 Paraplegic inactive SD 9.09 15.12 0.07 4.64 CI 32.7- 69.06- 1.7-1.78 23.01- 42.77 85.81 28.16 Mean 34 63.4 1.74 20.95 Tetraplegic active SD 8.31 9.61 0.03 2.89 CI 23.69- 51.47- 1.7-1.78 17.35- 44.31 75.33 24.54 Mean 37.25 76.98 1.78 24.11 Tetraplegic inactive SD 9.94 10.46 0.05 2.82 CI 30

. Figure 2 Apparent frequencies of a signal with a 0.3 Hz actual frequency component, sampled at 0.2, 0.3, 0.4 and 0.5 Hz are depicted. It is clear that due to aliasing the apparent frequency differs from the actual frequency in all cases. Irrespective of choice of estimation method for the impedance spectra, be it frequency sweep, multi-sine or other, longer estimation times yield better estimates; the more periods of the stimulation and sensing voltage/current, the higher signal-to-noise ratio (SNR). For slowly varying signals, e.g. body composition estimates, this

. A. Aguillon M.A. Rosell F. P. J. Carrera B. J Electrical Impedance Tomography: An Electronic Design, with Adaptive Voltage Measurements and A Phantom Circuit for Research in The Epilepsy Field Proceedings - 19th Internl Conf. - IEEE/EMBS Oct. 30 - Nov. 2 1997 867 868 USA 19 Henderson R. P., Webster J. G. An impedance camera for spatially specific measurements of the thorax. IEEE Transactions on Biomedical Engineering. 1978;Bme-25(3):250-254. 10.1109/TBME.1978.326329 Henderson R. P. Webster J. G An impedance camera for spatially specific measurements of the thorax

those obtained with the MT4080. Table 2 Capacitance C HL measured with the 4294A impedance analyzer and calculated body capacitance to ground C g for the four subjects and two feet heights above to ground: 10 cm (u) and direct outsole contact (d). Subject C HLu (pF) C gu (pF) C HLd (pF) C gd (pF) 1 22.5 95.4 18.2 153.0 2 23.5 85.1 17.8 159.7 3 24.8 72.9 20.5 119.2 4 25.5 66.8 20.2 123.2 Table 3 Capacitance C HL measured with the MT4080 LCR meter and calculated body capacitance to ground C g for the four subjects and two feet heights above ground: 10 cm (u

.05 1.49 2.91 13.09 2 1.65 3.77 20.10 6 2.55 5.06 24.96 20 6.62 10.38 24.03 60 15.78 20.25 34.16 100 20.05 23.81 44.28 The configuration of the electrodes also contributes to the increase in the measured admittance. For the four electrode setup there is no current flow through the voltage measurement electrodes, thus there is no voltage drop across these electrodes. This is illustrated by table (5) . Table (5) the influence of the three experimental setups (2-Inner, 2-Outer and 4- Electrodes) on the impedance and admittance values. Distilled Water Frequency (kHz

) Normal 30 0.939 ± 0.1 [0.821, 1.232] P < 0.001 P < 0.001 Osteopenia 15 0.736 ± 0.05 [0.657, 0.805] - P < 0.001 Osteoporosis 3 0.569 ± 0.07 [0.497, 0.631] - - Total Hip Z Scores Normal 30 0.9 ± 0.7 [-0.1, 2.6] P < 0.001 P < 0.001 Osteopenia 15 -0.8 ± 0.41 [-1.7, -0.1] - P < 0.001 Osteoporosis 3 -2.4 ± 0.86 [-3.30, -1.6] - - Total Hip T Scores Normal 30 -0.1 ± 0.74 [-1.0, 1.7] P < 0.001 P < 0.001 Osteopenia 15 -1.7 ± 0.39 [-2.3, -1.1] - P < 0.001 Osteoporosis 3 -3.0 ± 0.55 [-3.6, -2.5] - - Total Hip BMC (g) Normal 30 33.40 ± 7.25 [26, 62.03] P < 0.001 P < 0

positions: 2.5 mm radial centre-to-centre distance between the phantom and the chamber, (a) angle of 135° and (b) angle of 112.5°. The colour scale is in arbitrary units (from -1 in blue, to +1 in red) representing the T‐score. Potato releases starch in the surrounding medium over time, which may change the conductivity of the electrolyte in the region surrounding the object, additionally contributing to the inaccuracy in the image. As different biological tissues have different spectral properties, f-EIT gives the advantage that complex tissues, composed of, e.g., fat

Data analysed BIS SFBIA ICC r Bias a (%) b 95%CI Bias c (%) d Lower Upper R (ohm) 848±74 596±103 -0.02 -0.12 252+134 (35.5+18.9) 209 to 294 (29 to 42) -10 513 Xc (ohm) 86±9.3 63±9.5 -0.03 -0.12 23+14 (31.1+18.1) 19 to 28 (25 to 37) -4.6 51 PA ( ₒ ) 5.8±0.5 6.1±0.6 0.12 0.09 -0.3+0.8 (-4.8+12.6) -0.5 to -0.05 (-8.9 to -0.7) -1.8 1.2 TBW (L) 27±3.9 30±4.1 0.38** 0.47** -3.4+4.1 (-11.7+14.3) -4.7 to -2 (-16 to -7.1) -11 4.7 ECW (L) 11±1.4 14±2.2 0.20* 0.47** -2.9+2 (-22.8+14.8) -3.6 to -2.3 (-28 to -18) -6.8 0.9 ICW (L) 16±2.6 16±1.9 0.45** 0.44** -0.4+2.5 (-3

calculated by the Student t-test, with p< 0.05 indicating a statistically significant difference between males and females FM: fat mass. FFM: fat-free mass. TBW: total body water. Table 2 Correspondence between the cutoff points of the BMI (kg/m 2 ) and body fat ranges (%) according to Gallagher et al (2000). Fat mass (%) BMI (kg/ 2 ) Total < 18.5 18.5 – 24.9 25 – 29.9 ≥ 30.0 Men (%) < 8 3.1 (12) 4.6 (18) 0.5 (2) 0 (0) 8.3 (32) 8–20 3.9 (15) 29.3 (113) 11.6 (45) 1.8 (7) 46.6 (180) 20 – 25 0.5 (2) 6.7 (26) 10.1 (39) 2.8 (11) 20.2 (78) > 25 0.3 (1) 4.4 (17) 10.4 (40) 9.8 (38

, 23 , 24 , 25 , 26 ). Most EIS systems consist of applying a multi-frequency sinusoidal current of constant amplitude into the tissue sample, measuring the resulting potential, and then calculating the transfer impedance (Z t ) ( 14 , 15 ). In order to get accurate calculated transfer impedances, it is necessary to ensure that the injecting current has a constant amplitude over a wide frequency range, which may be obtained by using a current source with high output impedance ( 14 , 15 ). However, stray capacitances are known reduce the current amplitude at higher