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• 1928 - Cole: three-component electrical equivalent circuit
• 1998 - Electric changes before physiologic symptoms (REN et al.)
• 1999 - Impedance deviations between healthy and seek individuals (SIMONS et al.)
History
• Ionic current• Polarization • Resistive and capacitive characteristics• Specific values for each organ• Asymmetric measurement
Biologic Tissues Impedance
Tissues Equivalent Circuit (Cole)
Músculo (longitudinal)Músculo (transversal)Fígado
PulmãoBaçoIntestino
Measurements
• Wireless
• With electrodes• Invasive (needles)
• Non-invasive
Detector
Osciladorde
100 kHz
Amplificadorde potência
Bobina deexcitação
Bobinas de medida
• Signal Multiplication
Measurement
cos )
Filtro passa
baixa
Componente
em fase
s(t)Filtro passa
baixa
Componenteem
quadratura
cos(wt)
Low passfilter
Phasecomponent
Vi
s(t) Quadrature
componentLow pass
filtersin(wt)
• Discrete Fourier Transform - DFT
Measurement
1
0
2cos).(2 N
k Nkks
Nx
1
0
2sin).(2 N
k Nkks
Ny
22 yxA
xyarctan
• Plethysmography• Cardiography• Pneumography
• Total Body Water (TBW)• Cell Aggregation• Electrosurgery• Blood clotting analysis• Electrical Impedance Tomography (EIT)
Applications
Plethysmography - Cardiography
Blood´s resistivity(130 ~150 );
Distance between electrodes
Stroke blood volume
• Cell Impedance Monitoring with Interdigital electrode structures (IDES)
Cell Aggregation
50µm
0.5µm
0,5-5 µm current flow
10 µm
Substratum (Sapphire, Silicon)
Electrode (Platinum, Palladium)
• Cell Impedance Monitoring with Interdigital electrode structures (IDES)
0 5 10 15 20 25
0
1
2
3
impedance
pH
pO2
met
abol
ism
(rel
ativ
e ch
ange
s)
time [h]
50
100
150
200
250Cytochalasin B [2µM] present
Capacitance [nF]
Cell Aggregation
• Bacteria BiosensorBacteria Atraction
AC Voltage Source
SubstractBacteria Measurement
AC Voltage Source
Substract
Cell Aggregation
Electrical Impedance Tomography Reconstruction
Ab = I
1
1( , ) , , 1,2,...,
l
L
i j i jell
i j dr dS i j Nz
B
11 1
1 1( , ) , 1,2, ..., ,j
i ije e
i j dS dS i Nz z
C
1
1
11
1 1
| |
( , ) , , 1,2, ..., 1| || | j
j
e i jz
i j i j Lee i jz z
D
| |le Electrode area i Basis function
( 1) ( 1)
( 1)
( 1)
N L N L
N L P
N L P
A
b
I
1, 2,..., 1j L
N-Nodes, L-Electrodes, m-elementsP-Patterns
1 2
34
N
1
L
1 2
34
N
1
L
2
DNNCNCNB
A TT
βα
b
IN0
I ˆ~
T
PNα PL )1(β
100
010001111
,,, 121
LnnnN
N
iii
h yxyxuu1
,,
1
1
L
jjj
hU n
Potential inside:
Potential on electrodes: