What is the role of Electrical Impedance Tomography (EIT) in Early Detection of Breast Cancer?

What is the role of Electrical Impedance Tomography (EIT) in Early Detection of Breast Cancer?
An online interview with Alexander Hartov PhD, Thayer School of Engineering, Dartmouth College, Hanover, USA. 27 Jan 2006

About Alexander Hartov
Alexander Hartov is an electronics and biomedical engineer by training. He is the Research Associate Professor of Engineering at Dartmouth College in the USA, where he works in collaboration with physicians. His area of specialisation concerns instrumentation for medical application and more specifically the use of impedance measurements to screen for cancer. He also works in the field of image guided surgery. His involvement with electrical impedance tomography started in 1996 when he joined the faculty at Dartmouth.

Alexander Hartov in this online interview speaks from the view point of a scientist and Radiology Malaysia thanks him for sparing time to talk about his research in EIT.

The views expressed are his and does not necessarily represent or reflect the views or policies of the institution where he works. The content in this article does not replace consultation with your health professional.

Question: In Malaysia, EIT appears to have invaded the market, and used even in beauty and slimming saloons as part of their package of value added services for women. Advertisements alluding to “breast cancer screening” without pain and radiation have surfaced. Younger women, even in their late teens (from 15 years) have been included in the group that can benefit from Breast EIT.

Hartov: I concur with your outrage at screening wantonly women as young as 15. This is preposterous, no matter how innocuous the technology. In the US the recommended age for starting screening with mammography is somewhere between 40 and 50 years. Of course family history and other factors indicating a predisposition may require starting screening mammograms at a younger age. Screening the 20-40 years group is simply a waste of time if no indications exist. I will add that it's a waste of resources from a public health policy perspective, but it's also lucrative from the provider's perspective, which explains why it is offered as part of packages by businesses such as beauty and slimming salons.

Question: What exactly is electrical impedance tomography, especially with reference to the breast? I note there are a variety of terms used for the scans – T scan, Electrical Impedance scanning, Electrical impedance tomography. Is there a difference between these various types of “equipment used”?

Hartov: Here is a brief explanation of electrical impedance and how it relates to breast cancer screening. All tissue exhibit electrical properties which affect how well they conduct electrical currents (conductivity) and how well they can retain electrical charge (permittivity). This is not a special attribute of tissues, all materials have those properties and their magnitude qualifies them as conductors (very high conductivity) or isolators (very low conductivity). Materials with very high permittivity are used in the electronics industry to make capacitors, for example.

By applying a current on a person's skin, one can measure the effective impedance of the tissue traversed by the current. The impedance represents the effect of both conductivity and permittivity on the current flow. By applying many electrodes to a patient's breast (for example) and measuring the currents flowing through each electrode, it is possible to reconstruct a "map" of the tissue impedance variation. This image can reveal areas of high conductivity, which in the breast are associated with tumors. The whole process is non-invasive and innocuous, since the currents are too small to cause any harm and no radiation is involved.

There remain quite a few issues regarding the use of impedance measurements. First it has not been established clinically that it can discriminate reliably between benign (non cancerous) and malignant (cancerous) abnormalities in the breast. It is clear from direct invasive in-vivo (within a living organism) measurements that differences exist that may be used for screening. However, when making measurements non-invasively, the spatial resolution and sensitivity may not be sufficient to discriminate reliably. We are precisely in the process of conducting such clinical studies.

There are a few techniques to perform the measurements and the reconstruction of the impedance maps. We use a tomographic reconstruction approach. The Russian device uses a much simpler approach in which the electrode array is presented the way it looks spatially with the impedance magnitude reading represented in a gray scale image. A light spot (high conductivity) is considered an anomaly.

The T-scan device belongs in the same category, although its reconstruction method is somewhat more sophisticated in that it can reconstruct planes parallel to the electrode array at various depths. The thing to know about those planar array devices, the T-scan in particular is that they are not approved for screening by themselves (in the US). The studies that have been conducted with these devices were based on coupling the use of the T-scan with mammography. When used in this manner, that is the T-scan is used only on patients with an abnormal mammographic finding, the combination of mammo + T-scan improves the overall accuracy of screening. By itself, it does not qualify as a screening device.

Question: There has been some reports – eg Electrical Impedance Scanning for the Early Detection of Breast Cancer in Young Women: Preliminary Results of a Multicenter Prospective Clinical Trial, Journal of Clinical Oncology, Vol 23, No 12 (April 20), 2005: pp. 2703-2715 & Technology review: The use of electrical impedance scanning in the detection of breast cancer, Breast Cancer Res 2004, 6:69-74. There may be a role for young women with dense breasts. What are your comments?

Hartov: Also important, as I'm sure you know, is the fact that x-ray mammography is far from perfect and results in significant numbers of false positives and a few false negatives, which is why people are striving to find better screening methods. Not much in the way of improvement has been found to date. One category of patients in which it fails at an even higher rate is those women with denser breasts. It is thought that EIT may constitute to improve screening in that group.

Question: Does this problem of misleading advertisements (to the best of your knowledge and experience) exist in other countries? If so, what steps are being done elsewhere to curb misleading claims and what legislation or rules are there in place.

Hartov: As for curbing unsubstantiated claims, lying and cheating to make a buck is going to be with us for some time, I'm afraid. Strong legislation regarding devices for medical use does help, when it comes to public health policies.

Question: Perhaps, you have at take home message for Malaysians on the issue of electrical impedance?

Hartov: My take home message for people considering undergoing EIT is that it's still experimental. If your local beautician is offering it, you should ask yourself what are that person's qualifications to operate such a device and interpret the results it produces. I would recommend you change beautician and talk to a bona fide health care worker about your needs for screening. If you are under 40 and no one in you family has had breast cancer, you most likely don't need to worry about it yet.


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