Robust Linearized Image Reconstruction for Multifrequency EIT of the Breast

Abstract

Electrical impedance tomography (EIT) is a developing imaging modality that is beginning to show promise for detecting and characterizing tumors in the breast. At Rensselaer Polytechnic Institute, we have developed a combined EIT-tomosynthesis system that allows for the coregistered and simultaneous analysis of the breast using EIT and X-ray imaging. A significant challenge in EIT is the design of computationally efficient image reconstruction algorithms which are robust to various forms of model mismatch. Specifically, we have implemented a scaling procedure that is robust to the presence of a thin highly-resistive layer of skin at the boundary of the breast and we have developed an algorithm to detect and exclude from the image reconstruction electrodes that are in poor contact with the breast. In our initial clinical studies, it has been difficult to ensure that all electrodes make adequate contact with the breast, and thus procedures for the use of data sets containing poorly contacting electrodes are particularly important. We also present a novel, efficient method to compute the Jacobian matrix for our linearized image reconstruction algorithm by reducing the computation of the sensitivity for each voxel to a quadratic form. Initial clinical results are presented, showing the potential of our algorithms to detect and localize breast tumors.

Direct EIT Reconstructions of Complex Admittivities on a Chest-Shaped Domain in 2-D

“…We consider two choices of current patterns in our simulations. The first are the trigonometric patterns, (4) where denotes the total number of electrodes, , and is the current on the th electrode corresponding to the th current pattern. The second is the adjacent current pattern, a pairwise activation pattern otherwise.…”

“…Reconstruction algorithms for complex admittivities based on an iterative least-squares approach are found in [4], [15], [30] and an iterative package for 3-D reconstructions has been published in [42]. Another approach to the inverse problem is that of shape-based reconstruction methods for determining the location and shape of inclusions in the plane of the electrodes.…”

Regional Admittivity Spectra With Tomosynthesis Images for Breast Cancer Detection: Preliminary Patient Study

“…We have validated this geometric approximation using saline-tank experiments with a specially constructed breast-shaped tank [25]. The application of currents on the electrodes of the top plane, where z = 0, induces a current density distribution at the top plane, denoted by j t and can be written as $$\gamma \frac{\partial U(x,y,0)}{\partial z}=j^t(x,y).$$ The superscript t implies the top plane, and b implies the bottom plane.…”

A Bimodal Reconstruction Method for Breast Cancer Imaging

“…Tomographic EMI techniques generate an impedance (or conversely admittance) distribution map of the breast region, in which the presence of malignant lesions can be quantitatively assessed [3][4][5][19][20][21][22][23]. A recent study has shown that multi modality EMI approaches have an increased sensitivity and sensibility compared to individual EMI techniques [3].…”