Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-06-20
2003-12-16
Shaw, Shawna J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S475000
Reexamination Certificate
active
06665557
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to methods and apparatuses for imaging objects in turbid media and relates more particularly to a novel method and apparatus for imaging objects in turbid media.
As can readily be appreciated, there are many situations in which the detection of an object in a turbid, i.e., highly scattering, medium is highly desirable. For instance, the detection of a plane in fog is highly desirable for obvious reasons. In addition, the detection of a tumor within an organ of the human body, such as the breast, is advantageous since the early detection of said tumor is useful in devising effective treatment protocols. Although X-ray techniques do provide some measure of success in detecting objects in turbid media, they are not well-suited for detecting very small objects, e.g., tumors less than 1 mm in size, or for detecting objects in thick media. In addition, X-ray radiation can present safety hazards to a person exposed thereto. Other tumor detection techniques involving the use of ultrasound, magnetic resonance and radio isotopes are similarly limited in their detection capabilities and/or create safety concerns.
An alternative technique used to detect objects in turbid media, particularly tumors in the body, is direct shadowgram imaging. Historically, in direct shadowgram imaging, visible or near infrared (NIR) light is incident on one side of a medium, and the transmitted light emergent from the opposite side of the medium is used to form a transillumination image. Alternatively, the backward propagating light emergent from the same side of the medium may be used to form a back-propagation image. A difference in optical properties, such as absorption, emission, or scattering between the object and the turbid medium, provides the basis for the formation of an image. Objects embedded in the medium typically absorb the incident light and appear in the image as shadows. Unfortunately, the usefulness of traditional direct shadowgram imaging as a detection technique is severely limited in those instances in which the medium is thick or the object is very small. This is because light scattering within the medium contributes to noise and reduces the intensity of the unscattered light used to form the shadow image.
To improve the detectability of small objects located in a turbid medium using direct shadowgram imaging, many investigators have attempted to selectively use only certain components of the transilluminating (or back-propagating) light signal. This may be done by exploiting the properties of photon migration through a scattering medium. Photons migrating through a turbid medium have traditionally been categorized into three major signal components: (1) the ballistic (coherent) photons which arrive first by traveling over the shortest, most direct path; (2) the snake (quasi-coherent) photons which scatter only slightly and arrive after the ballistic photons and which deviate, only to a very slight extent, off a straight-line propagation path; and (3) the diffusive (incoherent) photons which experience comparatively more scattering than do ballistic and snake photons and, therefore, deviate more considerably from the straight-line propagation path followed by ballistic and snake photons.
Because the ballistic and snake photons represent comparatively less distorted image information than do the diffusive photons, one approach to improving direct shadowgram imaging has been to selectively use the ballistic and snake photons to form the shadowgram image. This typically involves using various space-gating, time-gating or space/time-gating techniques to permit the detection of ballistic and snake photons, while rejecting diffusive photons. Examples of this approach are disclosed in the following patents and publications, the disclosures of which are incorporated herein by reference: U.S. Pat. No. 5,140,463, inventors Yoo et al., which issued Aug. 18, 1992; U.S. Pat. No. 5,143,372, inventors Alfano et al., which issued Aug. 25, 1992; U.S. Pat. No. 5,227,912, inventors Ho et al., which issued Jul. 13, 1993; U.S. Pat. No. 5,371,368, inventors Alfano et al., which issued Dec. 6, 1994; U.S. Pat. No. 5,644,429, inventors Alfano et al., which issued Jul. 1, 1997; U.S. Pat. No. 5,710,429, inventors Alfano et al., which issued Jan. 20, 1998; U.S. Pat. No. 5,719,399, inventors Alfano et al., which issued Feb. 17, 1998; Gayen et al., “Sensing lesions in tissues with light,”
Optics Express
, 4:475-80 (1999); Gayen et al., “Two-dimensional near-infrared transillumination imaging of biomedical media with a chromium-doped forsterite laser,”
Appl. Opt
., 37:5327-36(1998); Gayen et al., “Near-infrared laser spectroscopic imaging: a step towards diagnostic optical imaging of human tissues,”
Lasers in the Life Sciences
, 37:187-198 (1999); Gayen et al., “Time-sliced transillumination imaging of normal and cancerous breast tissues,”
OSA Trends in Optics and Photonics Series Vol.
21
on Advances in Optical Imaging and Photon Migration
('98), pages 63-66 (1998), edited by J. G. Fujimoto and M. S. Patterson, Optical Society of America; Dolne et al., “IR Fourier space gate and absorption imaging through random media,”
Lasers in the Life Sciences
, 6:131-41 (1994); Das et al., “Ultrafast time-gated imaging in thick tissues: a step toward optical mammography,”
Opt. Lett
., 18:1002-03 (1993); Hebden et al., “Time-resolved imaging through a highly scattering medium,”
Appl. Opt
., 30:788-94 (1991); Demos et al., “Time-resolved degree of polarization for human breast tissue,”
Opt. Commun
., 124:439-42 (1996).
An alternative approach to the direct shadowgram imaging techniques described above has been to make use of the diffusive photons which, although containing comparatively less of the direct signal information than the ballistic and snake photons, are more abundant than the ballistic and snake photons. An example of such a technique that makes use of the diffusive photons for imaging involves inverting the experimental scattering data obtained from various points in the medium using an inverse reconstruction algorithm. Examples of inverse reconstruction techniques are disclosed in the following patents and publications, all of which are incorporated herein by reference: U.S. Pat. No. 5,931,789, inventors Alfano et al.. which issued Aug. 3, 1999; U.S. Pat. No. 5,813,988, inventors Alfano et al., which issued Sep. 29, 1998; Cai et al., “Optical tomographic image reconstruction from ultrafast time-sliced-transmission measurements,”
Appl. Opt
., 38:4237-46 (1999); Cai et al., “Time-resolved optical diffusion tomographic image reconstruction in highly scattering turbid media,”
Proc. Natl. Acad. Sci. USA
, 93:13561-4 (1996); Arridge, “The Forward and Inverse Problems in Time Resolved Infra-Red Imaging,” in
Medical Optical Tomography: Functional Imaging and Monitoring
, SPIE, Vol. IS11, G. Muller ed., 31-64 (1993); Singer et al., “Image Reconstruction of the Interior of Bodies That Diffuse Radiation,”
Science
, 248:990-3 (1993); Barbour et al., “A Perturbation Approach for Optical Diffusion Tomography Using Continuous-Wave and Time-Resolved Data,”
Medical Optical Tomography: Functional Imaging and Monitoring SPIE Institutes
, Vol. IS11, G. Muller ed., 87-120 (1993); and J. Schotland et al.,
App. Opt
., 32:448 (1993).
Although the various approaches described above have enjoyed some measure of success, there is considerable room for additional improvements.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new method and apparatus for imaging objects in turbid media.
It is another object of the present invention to provide a method and apparatus as described above that represents an improvement in image quality with respect to existing direct shadowgram and inverse reconstruction imaging techniques.
It is still another object of the present invention to provide a method and apparatus as described above that has applicability in the detection of tumors and other abnormalities in human body parts, such as th
Alfano Robert R.
Gayen Swapan Kumar
Zevallos Manuel E.
Kriegsman & Kriegsman
Shaw Shawna J.
The Research Foundation of City College of New York
LandOfFree
Sprectroscopic and time-resolved optical methods and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sprectroscopic and time-resolved optical methods and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sprectroscopic and time-resolved optical methods and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3109153