TY - JOUR
T1 - Electromagnetic impedance tomography (EMIT)
T2 - A new method for impedance imaging
AU - Levy, Shai
AU - Adam, Dan
AU - Bresler, Yoram
N1 - Funding Information:
Manuscript received September 1, 2001; revised March 15, 2002. The work of Y. Bresler was supported in part by a Technion Visiting Professor Fellowship. Asterisk indicates corresponding author. S. Levy and D. Adam are with the Department of Bioengineering, Technion, Israel Institute of Technology, Haifa 32000, Israel. *Y. Bresler is with the Department of Electrical and Computer Engineering and the Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA (e-mail: [email protected]). Publisher Item Identifier 10.1109/TMI.2002.800573.
PY - 2002/6
Y1 - 2002/6
N2 - We propose a new impedance imaging method, electromagnetic impedance tomography (EMIT), in which the boundary electric potential measurements in electrical impedance tomography (EIT) are augmented by measurements of the exterior magnetic field induced by the currents excited in the object by the standard EIT procedures. These magnetic measurements can be obtained reliably and inexpensively by simple pickup coils located around the imaged cross section. We derive expressions for the forward problem and for the Jacobian of the measurements, and propose an iterative reconstruction algorithm using a squared error cost function. The performance of EMIT and EIT is compared in numerical simulations using a finite-element model for the conductivity distribution of several phantoms. Evaluation of the rank and condition of the Jacobian demonstrates that the additional magnetic measurements provided by a few pickup coils in EMIT turn an underdetermined EIT problem into a well-posed one with reasonable condition, or significantly improve the conditioning of the EIT problem when it is already fully determined. Reconstructions of various phantoms reveal that EMIT provides particularly significant visual and quantitative improvement (threefold to tenfold reduction in the root-mean-squared error) in the sensitivity at the center of the object, which is the area most difficult to image using EIT.
AB - We propose a new impedance imaging method, electromagnetic impedance tomography (EMIT), in which the boundary electric potential measurements in electrical impedance tomography (EIT) are augmented by measurements of the exterior magnetic field induced by the currents excited in the object by the standard EIT procedures. These magnetic measurements can be obtained reliably and inexpensively by simple pickup coils located around the imaged cross section. We derive expressions for the forward problem and for the Jacobian of the measurements, and propose an iterative reconstruction algorithm using a squared error cost function. The performance of EMIT and EIT is compared in numerical simulations using a finite-element model for the conductivity distribution of several phantoms. Evaluation of the rank and condition of the Jacobian demonstrates that the additional magnetic measurements provided by a few pickup coils in EMIT turn an underdetermined EIT problem into a well-posed one with reasonable condition, or significantly improve the conditioning of the EIT problem when it is already fully determined. Reconstructions of various phantoms reveal that EMIT provides particularly significant visual and quantitative improvement (threefold to tenfold reduction in the root-mean-squared error) in the sensitivity at the center of the object, which is the area most difficult to image using EIT.
KW - Condition number
KW - Electromagnetic
KW - Impedance tomography
KW - Inductive sensing
KW - Inverse problem
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U2 - 10.1109/TMI.2002.800573
DO - 10.1109/TMI.2002.800573
M3 - Article
C2 - 12166865
AN - SCOPUS:0036591486
SN - 0278-0062
VL - 21
SP - 676
EP - 687
JO - IEEE transactions on medical imaging
JF - IEEE transactions on medical imaging
IS - 6
ER -