Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-03-21
2002-02-05
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S473000, C600S476000, C250S338100, C250S341100, C250S358100, C250S360100
Reexamination Certificate
active
06345194
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to breast imaging devices and methods using non-ionizing radiation of narrow spectral bandwidth, particularly, enhancing the images obtained by such devices and methods.
BACKGROUND OF THE INVENTION
X-ray mammography based on film-screen or xeroradiographic detection has for years been commonly accepted as a mass screening technique for breast disease. However, certain risks are associated with x-ray examination since x-ray radiation is also ionizing. Because exposure to such ionizing radiation should be minimized, the frequency and number of exams should be limited. Therefore, when using x-ray examination it is important to screen a patient's breast properly on the first attempt.
In recent years, broad beam light sources (sometimes referred to as “light torches”) having a wide spectral bandwidth in the visible and infrared ranges have been used for breast imaging. Broad beam light transmitted through a breast is typically recorded by a video camera, converted to an analog signal and viewed on a video monitor, or is digitized and analyzed on a computer. However, the ability to discriminate between various tissue-types in a breast via this technique is reduced if the transmitted beam has a wide spectral bandwidth (i.e. contrast is lost). Light may be absorbed, transmitted, scattered, and/or reflected to different degrees by different tissue types making it difficult to obtain information about the nature of any of the tissue. In addition, resolution and contrast may be lost due to a large amount of scattered light being transmitted from the breast being imaged to the detector. Resolution of images resulting from broad beam light source imaging is far below that which can be obtained with x-ray imaging systems. Detection limits when using this technique have generally been of lesions no smaller than what a physician can detect by palpitation. Therefore, this technique is not particularly advantageous.
As the present applicants described in now issued U.S. Pat. Nos. 4,649,275, 4,767,928, 4,829,184, and 4,948,974, a collimated (i.e. focused) light (i.e. non-ionizing radiation) source of narrow spectral bandwidth (such as is generated by a laser, a waveguide, a phased array, etc.) can be used to produce a beam or a number of beams of small spatial dimensions appropriate for acquiring images of a breast with high spatial contrast resolution. The narrow spectral bandwidth improves the characterization of the composition of the breast material being imaged to be more detailed. More information can be obtained by acquiring additional images at other wavelengths with narrow spectral bandwidths.
For example,
FIGS. 1 and 2
depict an apparatus for mammographic (breast imaging) applications which entail using collimated light (i.e. non-ionizing radiation in the near ultraviolet, visible, infrared, microwave, etc.) of narrow spectral bandwidth to obtain high resolution images. Appropriate sources of light in the visible and near-infrared spectrum include lasers or filtered light sources. As is shown in
FIGS. 2
a
-
2
d
, it is preferred that the light source be positioned on one side of the breast to be imaged and a receiver, such as a photodetector, be positioned on the opposite side to record transmitted light. As is shown in
FIGS. 1 and 2
, it is preferred that the breast be compressed between compression plates. The amplitude of a light beam, as well as other possible properties such as beam coherence, polarization, angular and spectral distribution, will be altered by absorption, reflection and refraction as it propagates through the breast and plates. Image resolution can be controlled by adjusting the cross-sectional area of light beam(s) before and/or after transmission through the breast.
The electromagnetic properties of various normal and diseased breast materials may exhibit wavelength dependence. Thus, acquiring images at different wavelengths of light may aid in distinguishing tissue types and calcifications. As can be appreciated from
FIG. 1
b
, light beams of wavelengths &lgr;
1
and &lgr;
2
sent from sources
1
and
2
are incident normal or nearly normal to the surface of one compression plate. The transmitted light is attenuated by the two plates and the breast material and then detected. An image or images can be acquired by simultaneously translating one or more light source and detector combination past the breast. As is shown in
FIG. 1
b
, it is preferable that each light source emits a different wavelength of light (i.e. &lgr;
1
≠&lgr;
2
). If a single light source provides more than one distinct wavelength, then a means of separating the wavelengths (narrow spectral bandwidth filters such as absorptive glass, transmissive or reflective gratings, etc.) is preferably incorporated prior to light reaching the detector or a detector which is sensitive to only a subset of the wavelengths employed is preferably used.
High resolution images may be obtained with a variety of scanning techniques:
FIGS. 2
a
and
2
b
show a point beam or multiple point beam which could be used in a raster scan format. The transmitted light beam can be collimated by a simple air gap, fiber optics, amplified fiber optics, light-pipes, focused lenses, waveguides, focused arrays, masks, polarization filters, narrow spectral bandwidth filters (which can also be directionally sensitive), or mechanical apertures to minimize detection of scattered light. This approach can be extended to include a single line or multiple line scan format as shown in
FIG. 2
c
. High speed two-dimensional imaging is shown in
FIG. 2
d
. In this case collimation (such as fiber-optics or light pipes) can be introduced into one or both compression plates. In all cases collimation may be used to produce a beam or beams of small cross-section and directional nature. These attributes can be used to exclude transmitted scatter from the exit beam.
If two or more sources providing light beams of differing wavelengths are spatially separated as shown in
FIG. 1
b
, then narrow spectral bandwidth filters can be used between plate B and the detectors for each wavelength such that the detector for &lgr;
2
rejects light of wavelength &lgr;
1
which is scattered into the path of the &lgr;
2
beam. In this case the spectral filter functions as a collimator, rejecting a component of the transmitted beam which can only be attributed to scatter. This would be advantageous when continuous sources are utilized or sources are pulsed almost simultaneously. The ability to reject wavelengths outside of a narrow spectral bandwidth would allow the source for &lgr;
1
to be located closer to the source for &lgr;
2
, improving image acquisition speed. Of course, a narrow bandwidth spectral filter can also provide directional discrimination (for example, diffraction gratings, interferometers, etc.). Although using two sources with different wavelengths is described, two sources with different polarizations could be used.
By positioning source
1
(for &lgr;
1
) adjacent to source
2
(for &lgr;
2
) the scatter contribution from source
1
into itself (near the boundary with source
2
) can be estimated by measuring the &lgr;
2
component at the location of source
1
. This assumes that radiation of wavelengths X, and &lgr;
2
have similar scattering and absorption properties for the type of tissue being imaged. Another technique is to have sources
1
and
2
incident at the same location, but source
2
would be tilted with respect to source
1
.
The light which is transmitted and recorded by the detector represents the attenuated beam plus scattered light. The light entering and exiting the breast can be collimated by introducing a patterned (structured) collimator (e.g. through the use of masks) so as to reject much of the scatter component. Collimation can be introduced before the photodetector to reduce the level of this scattered light. The photodetector produces an analog signal which can be displayed or digitized for storage and analysis on a computer.
As is disclosed in a
Nelson Robert S.
Zach Reuven D.
Lyon & Lyon LLP
Smith Ruth S.
LandOfFree
Enhanced high resolution breast imaging device and method... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Enhanced high resolution breast imaging device and method..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Enhanced high resolution breast imaging device and method... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2983474