Surgery – Diagnostic testing – Measuring electrical impedance or conductance of body portion
Reexamination Certificate
1999-02-24
2002-02-26
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Measuring electrical impedance or conductance of body portion
C600S382000, C600S301000, C128S920000, C128S925000
Reexamination Certificate
active
06351666
ABSTRACT:
BACKGROUND OF THE INVENTION
A breast cancer investigation is usually triggered by the discovery of a breast mass, and although in many instances the mass is the result of a benign lesion, this is not discovered until a patient has often undergone a battery of diagnostic tests which are sometimes invasive. A need exists for a noninvasive, adjunctive method and device which will aid a physician in making a clinical decision as to whether or not additional diagnostic tests for breast cancer are warranted.
Breast cancer is thought to originate from epithelial cells in the terminal ductal lobular units of mammary tissue. The development of breast cancer results in regions of epithelial electrical depolarization within the breast parenchyma, which led to the theory that the measurement of skin surface electropotentials would provide data to indicate the presence of underlying abnormal proliferation indicative of cancer. Many methods and devices have been developed in an attempt to implement this theory.
For example, U.S. Pat. No. 4,328,809 to B. H. Hirschowitz et al. deals with a device and method for detecting the potential level of the electromagnetic field present between a reference point and a test point on a living organism. Here, a reference electrode provides a first signal indicative of the potential level of the electromagnetic field at the reference point, while a test electrode provides a second signal indicative of the potential level of the electromagnetic field at the test point. These signals are provided to an analog-to-digital converter which generates a digital signal as a function of the potential difference between the two, and a processor provides an output signal indicative of a parameter or parameters of the living organism as a function of this digital signal. For breast cancer detection, Hirschowitz et al. shows that a test electrode can be placed in each quadrant of a human female breast and that multiple measurements can be taken during a test period with each test electrode and a reference electrode. These multiple measurements are digitized, normalized, and summed to provide an average or mean output signal indicative of a parameter of the living organism under test.
Similar biopotential measuring devices are shown by U.S. Pat. No. 4,407,300 to Davis, and U.S. Pat. No. 4,557,271 and 4,557,273 to Stoller et al. Davis in particular discloses the diagnosis of cancer by measuring the electromotive forces generated between two electrodes applied to a subject.
Often, the measurement of biopotentials has been accomplished using an electrode array, with some type of multiplexing system to switch between electrodes in the array. The aforementioned Hirschowitz et al. patent contemplates the use of a plurality of test electrodes, while U.S. Pat. No. 4,416,288 to Freeman and U.S. Pat. No. 4,486,835 to Bai disclose the use of measuring electrode arrays.
Unfortunately, these previous methods for employing biopotentials measured at the surface of a living organism as an adjunctive aid to diagnosis, while basically valid, are predicated upon an overly simplistic hypothesis which is not effective for many disease states. The prior methods and devices which implement them operate on the basis that a disease state is indicated by a negative polarity which occurs relative to a reference voltage obtained from another site on the body of a patient, while normal or non-malignant states, in the case of cancer, are indicated by a positive polarity. Based upon this hypothesis, it follows that the detection of disease states can be accomplished by using one measuring electrode situated externally on or near the disease site to provide a measurement of the polarity of the signal received from the site relative to that from the reference site. Where multiple measuring electrodes have been used, their outputs have merely been summed and averaged to obtain one average signal from which a polarity determination is made. This approach can be subject to major deficiencies which lead to inaccuracy, particularly where only surface measurements are taken.
U.S. Pat. Nos. 4,955,383 and 5,099,844 to M. L. Faupel disclose a method and apparatus using electropotential differentials between averaged values provided by a plurality of different sensors. This method operates on the basis that maximum differentials between areas of diseased tissue and apparently normal tissue in other areas of a breast for a breast cancer investigation provide informative parameters not subject to the inaccuracy of previous methods.
Still, the accurate measurement of DC biopotentials for sensing disease, such as breast cancer, is very difficult to accomplish, for the DC potentials to be sensed are of a very low amplitude. Due to factors such as the low DC potentials involved and the innate complexity of biological systems, the collected data signals tend to include a substantial amount of noise which makes accurate analysis difficult. Also, biological systems are notorious for their complexity, nonlinearity and nonpredictability, and wide variations from the norm are not uncommon. Thus it is necessary to develop a method and apparatus for obtaining the necessary data from the measurement of biopotentials and then to extract and analyze pertinent information which is relevant to a condition under study.
In an attempt to accomplish this, the method and apparatus of the previous Faupel patents was combined with one or more preprogrammed neural networks as illustrated by U.S. Pat. No. 5,697,369 to D. M. Long Jr et al. and U.S. Pat. No. 5,715,821 to M. L. Faupel. With a neural network, data can be processed by several layers of interacting decision points or neurons. The network must be taught to recognize patterns from input data to produce a predictive output, and this can prove to be a complex and often time consuming process involving many variables. Therefore, a need has arisen for a simple method and apparatus for use in the analysis of female breast electropotentials to minimize the effects of noise on the measurement data and to compensate for the biologic variability which affects the measurement data. Past methods and devices have concentrated on developing accurate data from sensed biopotentials which will provide an indication of the probability that a malignancy exists. These methods have ignored the effects of various biologic variables such as menstrual status or timing of the menstrual cycle. (Electrical Potential Measurements in Human Breast Cancer and Benign Lesions; Tumor Biology, 1994, pages 147-152). However, in younger women (ages 18-56) with a palpable breast mass, the prevalence of cancer becomes lower as age decreases. The sensitivity of mammography is limited in this less than 56 age group due to the density of breast tissue. Because of this, a considerable degree of diagnostic uncertainty remains after physical examination and mammography, and as a result, the open biopsy procedure performed on women in this 56 year or under population yields a low percentage of malignancy diagnoses. Physicians dealing with breast cancer detection have a need for a noninvasive technique which will provide data to effectively aid them in reaching a clinical decision that a suspicious lesion is benign and does not require a breast biopsy while still providing an indication that malignancy is probable when such is the case so that a decision can be made to conduct a biopsy.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a novel and improved method and apparatus for sensing and processing electropotentials from a female breast which minimizes the effects of noise on the measurement data.
Another object of the present invention is to provide a novel and improved method and apparatus for sensing and processing electropotentials from a human subject which involves weighting the measured electropotentials to compensate for biologic variables.
A further object of the present invention is to provide a novel and improved method and apparatus for sensing and processing electropotential
Borgwardt Vera
Cuzick Jack A.
Davies Richard J.
Gadsby Peter D.
Housworth Craig M.
Biofield Corp.
Lateef Marvin M.
Mantis Mercader Eleni
Nixon & Peabody LLP
Sixbey Daniel W.
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