Download Modifying Electrical Impedance Tomography System (2)

 Presenter : Yu-Chun Hua
 Adviser : Dr. Ji-Jer Huang
 Date : 99.12.09
Paper review(1) purpose
 From :R. A. Stiz, P. Bertemes-Filho, A. Ramos, V. C. Vincence. “Wide
Band Howland Bipolar Current Source using AGC Amplifier “IEEE
LATIN AMERICA TRANSACTIONS, VOL. 7, NO. 5, SEPTEMBER 2009

Purpose
•
Optimizing the output impedance (Zout) and voltage controlled

•
current source (VCCS)
In this system, it uses a current source balanced (also called "bipolar“)
 Automatic gain control (AGC) : 自動控制增益放大器
Paper review(1) materials and
methods
 Howland Circuit
Paper review(1) materials and
methods
R2 R5  R3 

R1
R4
I out
Vin  R2

R3  R1
Paper review(1) results
Amplitude of the current source
output as a function of frequency,
using a load of 500 Ω.
Amplitude of the current source output as
a function of frequency, using a
capacitive load.
Paper review(2) purpose
From: Tushar Kanti Bera and J. Nagaraju ﹐” A Simple Instrumentation
Calibration Technique for
Electrical Impedance Tomography (EIT)
Using A 16-Electrode Phantom ” 5th Annual IEEE Conference on
Automation Science and Engineering Bangalore, India, August 22-25, 2009

Purpose
Intended to investigate the phantom responses for
different electrode geometry
Electrode array position in bathing solution column and
the instrumentation is calibrated accordingly
Paper review(2) materials and
methods
A.
B.
C.
D.
Instrumentation(VCO)
EIT-Phantom
Forward Solution with Forward Solver
Boundary Potentials Measurements
B. EIT-Phantom
All the lead wires are of
equal lengths
CGE or CME is placed at
the phantom centre and
connected to the ground
Prepared with a 0.5%(w/v)
solution of KCl
Practical biological phantom with stainless
steel electrodes
C. Forward Solution with
Forward Solver
 Forward Problem (FP) is the basis of EIT and it
is essentially to be solved to calculate the
boundary potential for estimating the conductivity
update (Δσ) for each iteration in Inverse Problem
(IP) .
 Studying the FP, for an EIT system, the
instrumentation error can be detected to eliminate
the noise in the voltage signal
for better image resolution .
Equation
A relation between the measured potentials and the domain
conductivity equation using FEM as:
  K   I 
[Ф] is the vector of nodal voltage
[K(σ)] is the transformation matrix which is a function of elemental
conductivities of the FEM mesh
[I] is the vector of currents at each nodes
Equation
F is the Jacobean matrix which formed from the transformation
matrix K and it is defined as:
F gh
V


g
ds
h
g = 1, 2 …number of element
h = 1, 2…M [M = (number of data measured per current
x (number of current projections)]
projections)