Chemistry: analytical and immunological testing – Cancer
Reexamination Certificate
1998-11-30
2001-06-26
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Cancer
C436S063000, C600S547000
Reexamination Certificate
active
06251681
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates generally to the detection of cancerous tissues, and, more particularly, to a method and apparatus for detecting cancerous tissues of the epithelium of a human sigmoid colon and rectum, and, as well, detecting early changes in such epithelium which indicate the epithelium will eventually evolve into polyps or cancer.
2. Description of Related Art
It has been suggested in the past to determine the presence of certain cancerous tissue in a human by passing an electric current of predetermined value through suspected tissue and determining the electrical impedance of such tissue as compared to normal tissue. Similarly, it has also been suggested in the past that premalignant tissues which would, if nothing intervened, result in either polyps or cancerous tissue could be detectable by determining a specific change in tissue electrical impedance relative to the impedance of normal tissues.
It is generally considered in the prior art that human tissues composed of abnormal cells (i.e., tumor, carcinoma) exhibit an increased electrical impedance as compared to the impedance of the same tissues, if healthy. Exemplary of approaches to detection of cancerous tissues following these considerations are U.S. Pat. No. 4,729,385, PROBE AND METHOD OF USE FOR DETECTING ABNORMAL TISSUES by R. J. Davies and R. D. Juncosa and U.S. Pat. No. 4,690,152, APPARATUS FOR EPITHELIAL TISSUE IMPEDANCE MEASUREMENTS by R. D. Juncosa. Also,
Arch. Geschwulstforsch
58: 105-111 (1988) discusses electrical parameters of the cervical epithelium, and
European Surgical Research
(22):86-92 (1990) is concerned with the bio-impedance of breast tumors.
In none of the known prior work has there been provided a fully satisfactory technique for determining when a tissue is cancerous by measuring its transepithelial electrical impedance. Moreover, even less correlation has been established in the past as to when a tissue that, by other tests, is not presently in a malignant stage, could by testing be found to determine or red flag the fact that it would eventually evolve into cancerous tissue.
SUMMARY OF THE INVENTION
It is a primary object and aim of the present invention to provide a method and apparatus for detecting the presence of cancerous tissues in a human bowel by measuring the transepithelial electrical impedance and comparing with a standard or normal value.
It is another object in accordance with the previous object to provide a method and apparatus for determining premalignancy of human bowel tissues by transepithelial impedance measurements.
In accordance with the practice of the present invention, there are provided method and apparatus for measuring the electrical impedance of samples of epithelium taken from the situs of a suspected tumor as well as at a site remote from suspect tissue. In the practice of this invention it has been found that the impedance (X
N
) of normal bowel epithelium taken from an individual not having cancer of the bowel or colon is significantly higher than the impedance (X
C
) measured across a tumor or measured across tissues immediately adjacent a tumor in an individual having cancer. Moreover, it has been found that the tissue impedance (X
D
at a distance from the tumor of an infected colon or bowel is greater than the control measurement X
N
. At the same time, it is clear that the impedance measurement X
C
is dramatically less than that measurement taken on the same bowel or colon wall some distance away.
Measurement of tissue impedance in accordance with this invention is an electrical series circuit impedance measurement consisting of the Ringer solution impedance between voltage sensing probes, and the impedance of basal laminae and remaining connective tissue that physically lie in a path with the epithelium under examination. It is known that human tissues can be viewed electrically as being resistive and capacitive but have substantially zero inductive properties, so that the measured impedance when an alternating current is applied exhibits a so-called RC electrical impedance characteristic.
In accordance with the described invention, specimens of human sigmoid colon and rectum to be tested are surgically obtained and placed in an oxygenated Ringer solution during transport to the test site. Then, the tissue after being stretched over a ring-shaped mounting base is treated with a further Ringer solution. Immediately prior to electrical test, the tissue “cartridge” is once again bathed by oxygenated physiological saline.
While maintaining the tissue cartridge in contact with a flow of oxygenated Ringer solution of a prescribed temperature and at relatively low hydrostatic pressure, low resistance voltage sensing electrodes are located in slightly spaced relation (e.g., 2 mm) to the tissue surfaces. Transepithelial impedance is measured using a standard voltage-current clamp which permits compensation for resistance of fluid between the voltage sensing electrodes. A composite waveform consisting of a large number of different frequency, equal amplitude signals is applied to the epithelium. The signal is applied a plurality of times in two frequency ranges (low, LF; high, HF). Specifically, a given series of LF waveforms are applied, keeping the final reading and discarding the others. Similarly, a series of HF waveforms are applied keeping only the final impedance reading. At all other times, the tissue is maintained (clamped) at a predetermined voltage. The transepithelial impedance for test purposes is essentially the difference between the LF and HF measurements.
Physiologically, these results are consistent with the replacement of normally functioning epithelial cells by immature cells with different ionic transport function and consequent changed electrical characteristics. The human data in connection with the practice of the present invention indicates there is a higher epithelial resistance away from the tumor compared to a control, and as an epithelium close to or at a tumor is examined the resistance is lower than that of normal epithelium.
REFERENCES:
patent: 4537203 (1985-08-01), Machida
patent: 4729385 (1988-03-01), Juncosa
patent: 4862092 (1989-08-01), Juncosa
patent: 5280429 (1994-01-01), Withers
patent: 5526808 (1996-06-01), Kaminsky
patent: 5720296 (1998-02-01), Cha
patent: 5720744 (1998-02-01), Eggleston
Davies Richard J.
Juncosa Robert D.
Netter George J.
Wallenhorst Maureen M.
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