IIRC Impedance Imaging Research Center Korea http iirc

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Basics of Bioimpedance and Admittivity Imaging Eung Je Woo Impedance Imaging Research Center (IIRC) Department of Biomedical Engineering, Kyung Hee University KOREA http: //iirc. khu. ac. kr

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Fundamental Quantity • • Length (dimension or size) in meter (m) Time (sequence or duration or interval) in second (s) Mass in kilogram (kg) Charge in coulomb (C) Temperature in kelvin (K) Amount of substance in mole (mol) Luminous intensity in candela (cd) • • • Mechanics Electromagnetics Optics Thermodynamics Chemistry January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Charged Particle and Charge Density • • Free electron and hole are mobile Unbounded ion and molecule are mobile Bounded atom and molecule are immobile but may vibrate Polar molecule has no net charge but dipole moment and may rotate • • Mass Charge Size Position

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Field • • • Space with nothing Space with a single charged particle Space with two charged particles Space with multiple charged particles Space with a charge density distribution z r Qr y x Q 0 January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Potential or Voltage • Space with electric field E(r) • Put a point charge at r 1 from the infinity (a reference point) • Move the point charge from r 1 to r 2 E(r) r 2 Qr r 1 Qr January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Conductivity and Resistance I I S l I I

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Permittivity and Capacitance +Q S +++++ l -----Q -Q ----- +++++ +Q

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Polarization, Permittivity and Capacitance +Q S +++++ l -----Q -Q ----- +++++ +Q

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Cell and Bio-impedance Extra-cellular Fluid Cell Membrane + +++ _ _ _ _ +_ _+ _+ _+ _ + Intra-cellular Fluid January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Conductivity and Permittivity of Tissues Extra-cellular Fluid Intra-cellular Fluid Cell Membrane

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Conductivity and Permittivity of Tissues • Tissues themselves – Molecular composition of cells – Shape and density of cells – Direction of cells – Concentration and mobility of ions – Amounts of intra- and extra-cellular fluids • Amplitude and frequency of current • Temperature

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Hepatic Tumor Conductivity Necrosis Fibrosis Normal Cells D. Haemmerich, S. T. Staelin, J. Z. Tsai, S. Tungjitkusolmun, D. M. Mahvi and J. G. Webster, “In vivo electrical conductivity of hepatic tumours, ” Physiol. Meas. , vol. 24, pp. 251– 260, 2003. Tumor

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Breast Tumor Conductivity Normal Tissue Lobular Carcinoma Ductal Carcinoma A. J. Surowiec, S. S. Stuchly, J. R. Barr, and A. Swarup, ”Dielectric properties of breast carcinoma and the surrounding tissues, ” IEEE Trans. Biomed. Eng. , vol. 35, no. 4, pp. 257– 263, 1988.

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Conductivity and Neural Activity • • Cole K S and Curtis H J 1939 Electrical impedance of the squid giant axon during activity J. Gen. Physiol. 22 649 -670 Cole K S 1949 Dynamic electrical characteristics of squid axon membrane Arch. Sci. Physiol. 3 253 -258 Adey W, Kado R and Didio J 1962 Impedance measurements in brain tissue of animals using microvolt signals Exp. Neruol. 5 47 -66 Van-Harreveld A and Schade J 1962 Changes in the electrical conductivity of cerebral cortex during seizure activity Exp. Neurol. 5 383 -400 Rank J B 1963 Specific impedance of rabbit cerebral cortex Exp. Neurol. 7 144 -152 Aladjolova N A 1964 Slow electrical processes in the brain Prog. Brain Res. 7 155237 Geddes L A and Baker L E 1967 The specific resistance of biological material: a compendium of data for the biomedical engineer and physiologist Med. Biol. Eng. 5 271 -293 Meister M, Pine J, Baylor, DA 1994 Multi-neuronal signals from the retina: acquisition and analysis J. Neurosci. Meth. 51 95 -106 Neural activity produces 3 -5% local conductivity changes at low frequency.

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Bio-electric Signal and Source Imaging Amplifier ECG Medical Instrumentation: Application and Design, 3 rd ed. , by J. G. Webster

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Bio-magnetic Signal and Source Imaging MEG f(r; t) J(r; t) W

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Defibrillation and Cardioversion R. S. Yoon, T. P. De. Monte, and M. L. G. Joy, “Measurement of thoracic current flow in pigs for the study of defibrillation and cardioversion, ” IEEE Trans. Biomed. Eng. , vol. 50, no. 10, pp. 1167 -1173, 2003.

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Transcranial Electrical Stimulation M. L. G. Joy, V. P. Lebedev, and J. S. Gati, “Imaging of current density and current pathways in rabbit brain during transcranial electrostimulation, ” IEEE Trans. Biomed. Eng. , vol. 46, no. 9, pp. 1138 -1148, 1999.

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Motivation and Goal • Physiological functions and pathological changes alter conductivity and permittivity values. • Neural activity induces changes in conductivity. • Source imaging needs conductivity values. • Electromagnetic stimulations need conductivity values. Cross-sectional Imaging of Conductivity, Permittivity and Current Density Distribution

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Trans-resistance i Ip=Im 0 p Vq=Rpq. Im 0 Zpq=Rpq 0 s q V Rpq depends on (1) electrode configuration (2) conductivity distribution, s (3) geometry (boundary shape and size)

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Trans-impedance i p s+jwe Ip=Im 0 Zpq=Zpq Vq=Zpq. Im q V Zpq depends on (1) electrode configuration (2) complex conductivity distribution, s+jwe (3) geometry (boundary shape and size)

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 KHU Mark 1 mf. EIT System 16 -Channel System 32 -Channel System T. I. Oh, E. J. Woo, and D. Holder, “ Multi-frequency EIT system with radially symmetric architecture: KHU Mark 1, ” Physiol. Meas. , 28, pp. S 183 -96, 2007. T. I. Oh, K. H. Lee, S. M. Kim, W. Koo, E. J. Woo, and D. Holder, “Calibration methods for a multi-channel multi-frequency EIT system, ” Physiol. Meas. , 28, pp. 1175 -88, 2007. T. I. Oh, W. Koo, K. H. Lee, S. M. Kim, J. Lee, S. W. Kim, J. K. Seo, and E. J. Woo, “Validation of a multi-frequency electrical impedance tomography (mf. EIT) system KHU Mark 1: impedance spectroscopy and time-difference imaging, ” Physiol. Meas. , 29, pp. 295 -307, 2008.

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) KHU Mark 2 mf. EIT System • • • Multiple current sources Multiple voltmeters No pre-determined electrode configuration Wide bandwidth Compact design January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Boundary Current and Voltage

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Contact Impedance Two-electrode Method Four-electrode Method

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Data Collection Protocol Neighboring Method January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Reciprocity January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Neumann-to-Dirichlet Data January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Linearity and Nonlinearity 1. Linearity between current and voltage for a fixed g 2. Linearity between voltage and cg for a fixed g 3. What are nonlinear? January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Complex Conductivity Problem i p s+jwe q V

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Complex Conductivity Problem Ip=Im 0 i p Zpq=Zpq Vq=Zpq. Im s+jwe q V

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Multi-frequency Data Collection i j+1 jth Current j k+1 s+jwe V k kth Voltage

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Mathematical Expressions 1) Injection current, voltage and complex conductivity 2) Current density 3) Magnetic flux density

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Forward Solver: Example using FEM [ m. A/mm 2 ] Jx Bx y s [S/m] Jy y [ m. V] [ m. A/mm 2 ] Jz x y By y u x [ m. A/mm 2 ] x [ Tesla] x y x [ Tesla] Bz x x y y B. I. Lee, S. H. Oh, E. J. Woo, S. Y. Lee, M. H. Cho, O. Kwon, J. K. Seo, J. Lee, and W. S. Baek, “Three-dimensional forward solver and its performance analysis for MREIT using recessed electrodes, " Phys. Med. Biol. , vol. 48, 1972 -1986, 2003. y

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Forward Solver: Example using FEM • White lines are current stream lines. • Black lines are equipotential lines. + + - -

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Forward Solver: Example using FEM • White lines are current stream lines. • Black lines are equipotential lines. + + - -

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Equipotential Lines at 100 k. Hz Saline Banana v (real part) h (imaginary part)

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Voltage and Current Density

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 EIT using Boundary Measurements Neumann (Boundary Current) Dirichlet (Boundary Voltage)

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Problem Definition in EIT S L I January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) td. EIT Imaging: Human Thorax January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Static Imaging in EIT Subject g* Injection Current Data Acquisition Computer Model gk Forward Solver System Image Reconstruction Measured Boundary Voltage Algorithm Computed Boundary Voltage

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Static Imaging in EIT l Image of absolute value of complex conductivity (s + iwe) l Must overcome the following problems – Geometry is unknown and varying. – Electrode positions are unknown and varying. – Very accurate forward model is needed. – Higher degree of measurement accuracy is needed.

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Difference Imaging in EIT l Image of change in complex conductivity with respect to time and/or frequency l Common systematic errors can be cancelled out – Unknown boundary geometry – Uncertainty in electrode position – Systematic artifacts l Applications are limited but there are enough of them

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Difference Imaging in EIT l If conductivity changes as boundary voltage changes accordingly as l When dg is small, l. Then, a difference image of dg is obtained as Time-difference (td. EIT) Frequency-difference (fd. EIT)

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) td. EIT Algorithm l Linearization l Misfit Functional l Algorithm January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 fd. EIT Algorithm : homogeneous complex conductivity at w 1 and w 2 : complex voltage with : frequency-difference image between w 1 and w 2

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Perturbation and Sensitivity qth Pixel g = s+jwe = 1 gq = 1+1=2 in Lq

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Sensitivity and Linearization g = Dx in Lx g = Dy in Ly

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Sensitivity Matrix and Lineariztion - E electrodes - Q pixels

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) Complex Sensitivity Matrix and TSVD January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Experimental Results: td. EIT and fd. EIT Perspex 16 -Channel mf. EIT (IIRC KHU Mark 1) Banana Metal Banana Imaging Objects TX 151 Banana

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Preliminary Experiment: td. EIT Tx 151 Pink object : 0. 391 S/m Green object : 0. 171 S/m Background : 0. 137 S/m Sponge conductivity : 0. 02 S/m Background conductivity : 0. 0217 S/m 4 cm 3 cm

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: Perspex (Insulator) l Time-difference with homogeneous phantom data as reference 50 Hz 100 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: Stainless Steel (Conductor) l Time-difference with homogeneous phantom data as reference Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: TX 151 l Time-difference with homogeneous phantom data as reference 50 Hz 100 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: Banana l Time-difference with homogeneous phantom data as reference 50 Hz 100 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: Cucumber l Time-difference with homogeneous phantom data as reference 50 Hz 100 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: Perspex and Banana l Time-difference with homogeneous phantom data as reference 50 Hz 100 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: Stainless Steel and Banana l Time-difference with homogeneous phantom data as reference 50 Hz 100 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 td. EIT and fd. EIT: TX 151 and Banana l Time-difference with homogeneous phantom data as reference 50 Hz 100 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz 100 k. Hz 250 k. Hz Real Part Imaginary Part l Frequency-difference with 100 Hz data as reference 10 Hz Real Part Imaginary Part 50 Hz 1 k. Hz 5 k. Hz 10 k. Hz 50 k. Hz

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Time-difference Imaging: Animal Thorax

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Time-difference Imaging: Human Thorax

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) td. EIT: Human Thorax At 1 k. Hz At 100 k. Hz At 250 k. Hz January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) fd. EIT between 1 and 100 k. Hz: Human Thorax January 2010

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Images of Air Distributions in Lungs Sitting Right Lateral Left Lateral R X Sitting Right Lateral Left Lateral

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Images of Stomach Motility Filling Emptying

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Brain Imaging A. T. Tidswell, A. Gibson, R. H. Bayford, and D. S. Holder, “Three-dimensional electrical impedance tomography of human brain activity, ” Neuro. Image, vol. 13, pp. 283 -294, 2001.

IIRC: Impedance Imaging Research Center, Korea (http: //iirc. khu. ac. kr) January 2010 Time- and Frequency-difference Imaging • Time-difference imaging – – – Pulmonary function Cardiac function Gastric emptying Fracture healing Epilepsy imaging • Frequency-difference imaging – Tumor imaging – Stoke imaging – Neural activity imaging