Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-01-29
2003-12-23
Manuel, George (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S407000, C250S358100
Reexamination Certificate
active
06668187
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to imaging devices used to detect breast cancer and more particularly to such imaging devices known as transillumination devices which use non-ionizing radiation such as optical radiation to image the interior of the breast.
BACKGROUND OF THE INVENTION
Transillumination imaging devices and methods (sometimes referred to as “optical mammography”) for diagnosis of breast lesions were first described in an article by Cutler in the Journal of Surgical Gynecology, Obstetrics Vol., 48:721 (1929). Transillumination imaging uses intensive non-ionizing radiation such as light that is detected after transmission through the breast and processed to provide image data from the interior of the breast.
The main motivating factor behind the use of transillumination for detection of breast cancer rather than x-rays has been the problems caused by the ionizing x-rays. For safety reasons it is recommended that the use of x-rays for detection of cancer generally be restricted to women age 40 and over and further be restricted to only one test per year. The use of non-ionizing radiation devices such as ultrasound or transillumination enables testing women under 40 as well as over 40 and is not restricted to use once per year. There are no negative safety repercussions derived from testing for breast cancer more than once a year using non-ionizing radiation.
U.S. Pat. No. 4,945,239 describes prior art transillumination devices and the problems inherent with such devices. An important problem with transillumination devices is that the low energy photons of the light beams are easily scattered and therefore produce blurred images. The transillumination prior art used many methods in attempting to reduce the scatter and to generally improve the transillumination images. However, the scatter reducing methods and devices described by the prior art are relatively complicated and difficult to use. For example, the aforementioned patent describes reducing scatter by using a pin hole box between the light source and the breast and again between the breast and the detector. This does reduce scatter, however, the pin hole boxes and light sources have to be very accurately aligned and even more detrimental is the fact that the procedure is time consuming because the pin hole boxes are used in a scanning regimen to image the breast interior.
U.S. Pat. No. 4,945,239 also describes using an unspecified marker that is opaque to an unspecified wavelength of light as a contrast agent
Another method of reducing scatter is through the use of complicated optical lens systems or polarizing filters between the light source and the breast and between the breast and the detector.
Yet another prior art scatter reducing procedure uses mirrors. A semi-permeable mirror is used between the light source and the breast to transport light to the breast and to a detector in conjunction with a phase conjugated mirror that receives light that has traversed the breast. The phase conjugated mirror sends the light back through the breast to the semi-permeable mirror and the detector. Thus, the prior art faced the problem of light scattering when transillumination was used to detect cancer in breasts by providing complicated systems such as complicated lens systems, mirror systems and pin hole systems.
The great difficulty in discovering lesions embedded in breast tissue by transillumination was highlighted in a theoretical investigation by Navarro et al. described in the Medical Physics Journal 15:181 (1988). That study concluded that lesions of 0.5 centimeter in size would not be detected by transillumination if located deeper than 0.5 centimeters from the skin surface because of scatter caused by the skin surface interface.
A prior art system used “time of flight” analysis to distinguish light beams traversing the breast in a straight line from the source to the detector from scattered light.
In the patents listed and analyzed in the above mentioned patent it seems that only U.S. Pat. No. 4,767,928 discloses obtaining planar or tomographic images. The planar image is obtained by rotating the light beams around the breast. The prior art does not acquire images by focusing on different planes illuminated by the light traversing the breast. The patents in general merely examine the light that makes it through the breast and does the imaging based strictly on the intensity of light traveling through the breast detected after traveling through the breast wherein the intensity of the light is used to obtain mainly shadowgraph images based on absorption and scatter. Thus the detected light is light that was not absorbed by the tissue is imaged. Where absorption is high; then the cause of the high absorption is attributed to a possible lesion. Thus if a lesion exists at some level in the breast the detection of the lesion is hampered by scatter and by variations in the overlying and underlying structure of the breast all of which are imaged together.
More recently in transillumination apparatus, broad beam light sources referred to as “light torches” have been used for breast imaging.
Again, the main problem is scatter. Spatial resolution and contrast are lost because of scatter. U.S. Pat. No. 4,948,974 acquires image data by focusing the light coming into the breast onto points in the breast and then moving the light source to scan different planar sections within the breast and to detect the light from those planes. This patent mentions the use of single wavelength illumination to reduce scatter, in contrast to the prior art which uses broadband illumination.
UK patent GB 2 111 794 inter alia describes a system in which a breast is illuminated by a collimated beam as from a projector or from a laser and an expander. Light passing through the breast is detected by either a contact detector or by a television camera. However, since collimated light is used for illumination, both detection methods provide only a shadowgraph of the breast.
In summary, the prior art may be divided into two broad categories. A first category of prior art systems images shadowgraphs of the breast without substantial specificity as to the depth. The second category focuses beams on a point in the breast and requires scanning to image the breast.
In general methods of detecting cancer in the breast using transillumination, use red visible light and/or infrared light, generally to detect patterns of increased vascularity which surrounds breast cancer. It is believed that such light is used because light (other than red) in the visible range is strongly attenuated by body tissues (especially by the blood).
SUMMARY OF THE INVENTION
The present invention is directed to non-ionizing radiation imaging system especially useful for mammography.
One aspect of some preferred embodiments of the invention provides for imaging of planes of the breast utilizing non-ionizing radiation. The advantages of this aspect of the invention is that it significantly reduces the effects of overlying and underlying structures in selectively imaging a plane of the breast, rather than imaging a shadowgraph. This is facilitated through the use of a special contact window primarily located between radiation detectors and tissue being imaged and by the use of a camera focused on a depth of a slice to be imaged.
In addition, in accordance with an aspect of some preferred embodiments of the invention, light in ranges other than red is used to image the breast. In particular, light of various limited ranges of wavelengths is used to selectively image the breast. The limitation takes advantage of the fact that different anatomical structures absorb different wave lengths of light energy to different extents. Breasts consist in large proportion of fatty tissue. The range of wave lengths used, i.e. 490-670 nanometers is centered around the wave length of minimal optical absorbency of the fatty tissue in order to assure sufficient light transmission for detection. In this wave length range the absorbency differences, i.e., the contrast between th
Fenster & Company
Manuel George
Pass Barry
Yissum Research Development Company of the Hebrew University of
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