Surgery – Diagnostic testing – Measuring anatomical characteristic or force applied to or...
Reexamination Certificate
2001-04-26
2003-09-16
Hindenburg, Max F. (Department: 3736)
Surgery
Diagnostic testing
Measuring anatomical characteristic or force applied to or...
Reexamination Certificate
active
06620115
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for the computerized mechanical palpation of the breast and detecting changes in mechanical properties of the breast tissue that are indicative of breast cancer and other breast pathologies accompanied by changes in the tissue viscoelasticity.
2. Description of the Related Art
Breast cancer is a major source of cancer morbidity and mortality in women. Various techniques have been developed for early diagnosis of breast cancer including ultrasonic imaging, nuclear magnetic resonance imaging, x-rays, and the like. Currently, the most widely used clinical method of diagnosing breast cancer is mammography. Efforts to reduce mortality via screening mammography have been successful with improvement in survival, particularly in women over 50 years old. One of the major disadvantages of the use of mammography is patients' exposure to radiation.
One of the safest and oldest techniques of detecting tissue disease is manual palpation. Palpation encompasses examination using the sense of touch, and is based on the significant difference in elasticity of normal and diseased tissues. Overall, about two-thirds of cancers are detected by palpation. Such sensitivity is related to significant changes in mechanical properties of tissues in the course of breast cancer development. In the United States the technique of self-palpation is widely taught to women as an effective means of early cancer detection. A significant fraction of breast cancer is first detected by women themselves who find suspicious lesions within their breasts and bring the problem to the attention of their physicians. The main disadvantage of manual palpation is its high degree of subjectivity. The examiner has to instinctively relate what he or she perceives by the finger to his or her previous experience. Moreover, a physician performing the examination cannot objectively record the state of the examined breast.
A number of devices have been developed for detecting regions of hardening in the breast tissues. Several authors have proposed various devices for breast palpation using different types of force sensors, but all with limited success. For example, a device described by Gentle in Gentle CR, “Mammobarography: A Possible Method of Mass Breast Screening”, I. Biomed. Eng. 10, 124-126, 1988 was capable of detecting ‘lumps of 6 mm in diameter in breast phantoms but was unable to obtain any quantitative data on lumps in a human breast. Many of the proposed breast self examination means were related to simple non-computerized mechanical systems enhancing sense of touch such as apparatuses described in U.S. Pat. No. 5,572,995, U.S. Pat. No. 4,657,021, U.S. Pat. No. 4,793,354, and U.S. Pat. No. D348,618.
Various types of devices mimicking manual palpation for detecting breast tumors using different types of force sensors have been developed. For example, Frei et al., U.S. Pat. No. 4,250,894, describes an instrument which uses a number of piezoelectric strips pressed into the breast during the examination by a pressurizing unit which applies a given periodic or steady’ stress to the tissue beneath the strips.
Another method and device for breast examination are described in the U.S. Pat. No. 5,883,634 and U.S. Pat. No. 5,989,199. The sensors used in this device are based on the force sensor array manufactured by Tekscan Inc., Boston, Mass. The array consists of conductive rows and columns whose intersecting points form sensing locations. A material, which changes its electrical resistance under applied force, separates the rows and columns. Thus, each intersection becomes a force sensor. Clinical data obtained using this device were published in February 1999 issue of the Oncology News International, in an article entitled “Electronic Palpation May Detect Breast Cancers”. The device showed an overall sensitivity of 92% (detecting 108 of 118 palpable and nonpalpable lesions) vs. 86% for the physician's exams (102 of 118 lesions). The device correctly detected all eight palpable cancers found in the study population and two of three non-palpable cancers.
Conventional imaging modalities capable of detecting motion of a tissue subjected to an external force (such as ultrasound or MRI) use indirect means of evaluation for determining the elasticity of the tissues. One such approach is based on determining the relative stiffness or elasticity of the tissue by applying ultrasound imaging techniques while vibrating the tissue at low frequencies. See. e.g., K. I. Parker et al, U.S. Pat. No. 5,099,848; R. M. Lerner et al.,
Sono
-
Elasticity: Medical Elasticity Images Derived From Ultrasound Signals in Mechanically Vibrated Targets
. Acoustical Imaging, Vol. 16, 317 (1988); T. A. Krouskop et al.,
A Pulsed Doppler Ultrasonic
241,
Rehab. Res. Dev
. Vol. 24, 1 (1987); and Y. Yamakoshi et al.,
Ultrasonic Imaging of Internal Vibration of Soft Tissue Under Forced Vibration
, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 7, No. 2, Page 45 (1990).
Another method proposed for measuring and imaging tissue elasticity is described in Ophir et al., U.S. Pat. Nos. 5,107,837, 5,293,870, 5,143,070 and 5,178,147. This method includes emitting ultrasonic waves into the tissue and detecting an echo sequence resulting from the ultrasonic wave pulse. The tissue is then compressed (or alternatively decompressed from a compressed state) along the path. During such compression a second pulse of ultrasonic waves is sent along the path into the tissue. The second echo sequence resulting from the second ultrasonic wave pulse is detected. Next, the differential displacement of the selected echo segments of the first and second echo sequences are measured. A selected echo segment of the echo sequence, i.e., reflected RF signal, corresponds to a particular echo source within the tissue along the beam axis of the transducer. Time shifts in the echo segment are examined to measure compressibility of various regions in the examined tissue.
All presently available methods of palpatory assessment of the breast are inferior to manual palpation in sensitivity and specificity. Therefore, further development of screening techniques with greater sensitivity, specificity and accuracy is urgently warranted. It is desirable to provide computerized palpation of the breast which is capable of detecting breast lesions with sensitivity and spatial resolution exceeding that of manual palpation for use in early diagnostics of breast cancer.
The invention will be more fully described by reference to the following drawings.
SUMMARY OF THE INVENTION
The present invention provides a device and method for detection of abnormalities in tissues accompanied by the changes in their elasticity (such as those caused by cancer). The method is based on a computerized mechanical imaging referred to herein as CMI. The essence of CMI is the reconstruction of the internal structure of the soft tissues in a human body by measuring a dynamic or oscillatory stress pattern using an array of pressure sensors. The pattern of the dynamic mechanical stress and its changes as a function of applied pressure and time contain comprehensive information on the mechanical properties and geometry of the internal structures of the studied tissues.
The CMI devices are applicable in those fields of medicine where palpation is proven to be a sensitive tool in detecting and monitoring diseases (including but not limited to the breast cancer.
In a preferred embodiment, the apparatus for mechanical imaging of the breast comprises an electronically controlled mechanical scanning unit with a number of pressure transducers and an electronic unit for data acquisition, processing and displaying of images. The mechanical scanning unit includes a compression mechanism, three-dimensional positioning system, and local pressure source with a linear pressure sensor array opposing a two-dimensional pressure sensor array. The local pressure source is either a roller that is moved ov
Egorov Vladimir
Sarvazyan Armen P.
Armed L.L.C.
Hindenburg Max F.
Mathews, Collins Shepherd & McKay, P.A.
Wingood Pamela L
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