Today, a variety of Tomography Modalities exists based on different physical aspects
Each serves a purpose while having drawbacks
Hybrid Tomography Modalities
- Today, a variety of Tomography Modalities exists based on different physical aspects
- Each serves a purpose while having drawbacks:
- MRI – long acquisition time, expensive
- CT – safety issues due to radiation
- US – low contrast
- EIT – low resolution, not stable
- Hybrid Modalities offer to combine the advantages of existing modalities while reducing drawbacks
The MAET modality
The Forward and Inverse problems
- We can separate the MAET tomography into two problems
- The Forward problem:
A model of the expected measurements, given the tissue’s impedance
- The Inverse problem:
The tissue’s impedance reconstruction, given the measurements
Project Goals
- We restrict ourselves to the Forward problem only
- Our goals are:
- Understand the MAET forward problem theory model
- Develop numeric tools specified to solve the forward problem
- Build a working model simulation of the MAET measurement
- Give predictions for future experiments
- The project will help in providing a database for the Inverse problem solution validation
- Moreover, the project will provide a starting point for future experiments settings
Projects Highlights
- Literature review of MAET Physical and mathematical model
- Implementation of the mathematical model in Matlab
- Implementation in Comsol
- Three tissue models
- Matlab-Comsol interface
- MAET measurement simulation
- Parametric sweep study
Simulations Results-Circular
Simulations Results-Elliptic
Simulations Results-Multi
Simulation Conclusions
- The conductivity map is the main factor which determines the measurement profile
- Different model width leads to measurement scaling
- Variation in Electrodes size has negligible effect
- Variation in Electrodes position results in different measurement profile
- Dispersion has minor effect on measurement profile
- Expected voltage scale is in milliVolt to microVolt ,time in microseconds
Summary
- Hybrid tomography modalities
- MAET forward problem formulation and theory
- Implementation of Poisson solver in Matlab in different coordinate systems
- Maet simulation in Matlab
- Comsol usage and integration with Matlab
- Various tissue models simulation and comparisons
- Experiment oriented conclusion
Further Study
- Detailed ultrasound model
- Theory validation in a real world experiment
- MAET inverse problem simulation
Forward Problem Theory
- Starting assumptions:
- Quasi-staticRegime
- Ultrasound wave can be focused on to a very small volume
- Controllable constant magnetic field
- Tissue electro-neutrality
- No outgoing current in tissue boundary beside probes
References
- S. Haider, a Hrbek, and Y. Xu, “Magneto-acousto-electrical tomography: a potential method for imaging current density and electrical impedance.,” Physiol. Meas., vol. 29, no. 6, pp. S41–S50, 2008.
- H. A. Haus and J. R. Melcher, “Electromagnetic Fields and Energy,” Massachusetts Institute of Technology. [Online]. Available: http://web.mit.edu/6.013_book/www/chapter7/7.2.html. [Accessed: 07-Sep-2015].
- L. N. Dworsky, Introduction to Numerical Electrostatics Using MATLAB, 1st Edition. Wiley-IEEE Press, 2014.