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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