9 4 - bioimpedance - 60 min

Bioimpedance

• 1780 - Galvani: frog muscle movements

• 1850 - Helmholtz: nerve cell conduction velocity

History

• 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

Definition

fCXc

21

fLXl 2

• Ionic current• Polarization • Resistive and capacitive characteristics• Specific values for each organ• Asymmetric measurement

Biologic Tissues Impedance

Biologic Tissues Impedance

Body Measurements (50 kHz )

Frequency Analyses

ECF – Extra Cellular FluidICF – Intra Cellular Fluid

Frequency Analyses

Tissues Equivalent Circuit

Tissues Equivalent Circuit (Cole)

Músculo (longitudinal)Músculo (transversal)Fígado

PulmãoBaçoIntestino

Body Impedance Spectrum

Measurements

• Wireless

• With electrodes• Invasive (needles)

• Non-invasive

Detector

Osciladorde

100 kHz

Amplificadorde potência

Bobina deexcitação

Bobinas de medida

Bipolar

Electrode Configuration

Tetrapolar

Tetrapolar

Electrode Configuration

• 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

Block Diagram

Safety

Current: limit 800 μA to 500 μA (IEC60601-1 norm)

• 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


• Stroke blood volume

Total Body Water

Eletrodos de sinal

Eletrodos

de medição

Impedance Body Composition

Lean Mass

Fat Mass

FM = weight - LM

Impedance Body Composition

Diagnostics

50 kHz

• 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

• Bacteria Biosensor

Cell Aggregation

Electrosurgery

Blood Clotting analysis

Blood Clotting analysis

Thrombocyte agrregationQuick-Wert, PT, INR

Electrical Impedance Tomography (EIT)

Electrical Impedance Tomography

Electrical Impedance Tomography Block Diagram

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:

Electrical Impedance Tomography

Questions

9 4 - bioimpedance - 60 min

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