Electrical Impedance Tomography

An IPRPI Project
Researchers within the Inverse Problems Center at Rensselaer Polytechnic Institute (IPRPI) aim to improve early detection of breast cancer by developing an innovative new tool.

This tool, called the Fourth Generation Adaptive Current Tomography (ACT4), uses electrical impedance tomography (EIT) to offer a pain-free method of detecting tumors.

The EIT team is jointly led by Dr. David Isaacson, Rensselaer professor of mathematical sciences, Dr. Jon Newell, Rensselaer professor of bioengineering and Dr. Gary Saulnier, professor of electrical, computer, and systems engineering. About 8 Rensselaer students also contribute to the project.

ACT4 Description
Members are developing ACT4 to be capable of delivering real-time or still images of the electrical state of a breast's interior through exterior measurements.

The ACT4 system is intended as a complement to mammography in order to locate abnormalities that could otherwise be overlooked, as well as to eliminate the need for some biopsies.

The device contains 64 electrodes attached to a box roughly two feet square and 4 feet high.

How ACT4 Works

• Step One: Currents are transmitted through the surface of the breast.
• Step Two: A computer measures and records the voltages required for the current to pass through the tissue.
• Step Three: A mathematical algorithm is used to reconstruct and display the internal conductivity on a contrasting color or gray-scale image.

Reading the Results
Tumors conduct electricity four or more times better than normal tissue, therefore radiologists easily may distinguish between regular and abnormal tissue. Cancerous tumors appear white on a gray scale, or they appear blue when normal breast tissue is red in a color image.

Sensitivity and Specificity
The ACT4 is designed to detect inhomogeneities or spheres as minuscule as 3mm in diameter within a 10cm-cubed volume and those with a conductivity of two or more times that of normal tissue.

The tool is expected to more effectively detect small tumors and to improve radiologists' ability to determine whether or not a tumor is malignant.

Three Dimensions
This pioneering system offers considerable enhancements over currently available electrical impedance tomography technology by providing data in three dimensions. In comparison, the Israeli T-Scan displays data on only one plane.

In clinical trials, the T-Scan has been shown to detect cancer 22 percent more often when combined with mammography; 16 percent of patients would have been able to avoid undergoing a biopsy.

With its multidimensional image output, the ACT4 is expected to provide even greater improvements to breast cancer detection than the T-Scan, when also used in conjunction with mammography.

EIT researchers do not expect the tool to replace mammography, and say that the two technologies may have their own merits in detecting different types of tumors.

Future Plans
Dr. Newell is expecting to begin conducting patient trials for the ACT4 in late 2005 at Massachusetts General Hospital in Boston. Dr. Daniel B. Kopans, Professor of Radiology and Director of breast imaging, will collaborate in these studies.

Researchers' long-term plans for the ACT4 call for modifications to facilitate its use for the tool's initial purpose – the detection of abnormalities in heart and lung functions. Members say that the ACT4 could be used for those diseases as well; however, their efforts currently are focused on breast cancer.

EIT researchers hope that the ACT4 will one day offer patients a welcome complement to mammography technology, resulting in fewer biopsy surgeries and less unnecessary anxiety due to inaccurate readings. With the additional advantages of the ACT4's low cost and no known side effects, the device has great potential to become an effective and valuable tool in the critical fight against breast cancer.

Current Funding
Rensselaer's Center for Subsurface Sensing and Imaging Systems (CENSSIS) is among the primary funding sources for the researchers' work in this inverse problem.
The National Insitute for Biomedical Imaging and Bioengineering of the NIH is the primary funding source.

Research Team Members:
Rensselaer Faculty
David Isaacson
Jonathan Newell
Gary Saulnier

Post-doctoral Fellows
Tzu-Jen Kao
Borg Seok Kim

Doctoral Students
Chandana Tamma
Ning Liu
Roger Xia

Master's Student
Rujuta Kulkarni

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Inverse Problems Center at Rensselaer
Rensselaer Polytechnic Institute, 110 8th St., Troy, NY 12180-3590.
(518) 276-2145• E-mail: mclauj3@rpi.edu