Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-09-18
2001-06-05
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S476000, C600S477000, 36, 36, 36, C250S358100, C250S360100, C250S341300, C250S358100
Reexamination Certificate
active
06243601
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to transillumination imaging instrumentation used in the biological setting and, more particularly, to improvements in the design of transillumination imaging devices to prevent scattered light from adversely affecting detection performance, and provide a more useful format for imagery.
2. Description of the Prior Art
Transillumination involves the use of non-ionizing radiation, preferably having wavelengths ranging from 500 nm to 1500 nm, to image an object. Similar to an X-ray, transillumination involves passing radiant energy through an object, and detecting transmitted or reflected radiation. Detection can be accomplished using photocells or other electronic devices, or using photographic film or other image capturing materials. However, particularly when biological imaging is being performed (i.e., breast imaging, teeth imaging, etc.), transillumination offers the advantage of non-ionizing radiation compared to the ionizing radiation used in X-rays which is now widely believed to cause the induction of various cancers. However, one of the drawbacks of using non-ionizing radiation is that it is more easily scattered than ionizing X-rays, thus making it difficult to detect small structures in an object being imaged.
U.S. Pat. No. 4,945,239 to Wist et al., which is herein incorporated by reference, describes several concepts for distinguishing light which passes straight through a sample from light which is scattered from other sources. One method involves using a pair of pin-hole boxes in front of and behind the object being imaged whereby scattered light must traverse straight though spaced apart pin holes in order to reach a detector. Another method involves separately activating an emitter-detector pair, among a plurality of pairs in an array, whereby the timing of activation of the selected emitter-detector pair is used to assure that the light beam passes straight through an object. A variation on this method is to use shutters in front of a detector module whereby the timing of opening the shutter is matched to light emission from a specific emitter. The shutter scheme contemplated in Wist et al. can also be matched to the time of flight of the light through the object. Still another method involves positioning matched polarization filters on either side of an object, whereby scattering events that occur within an object change the plane of polarized light such that it no longer matches the filter positioned in front of a detector and the scattered light is not detected. Phase plates with a plurality of adjacent polarized regions can be used in combination with emitter and detector arrays, thereby eliminating the need for mechanically moving a light source.
In recent years the use of three dimensional modeling or imaging has become a useful and popular tool in many fields including the medical field. This popularity is due in part to the increased ability of computers to receive and process large amounts of raw data required for three dimensional images. Transillumination imaging is useful not only for detection but for providing detailed locations of anomalies in body parts. Using transillumination to form a three dimensional image provides more information than would be possible with a mere two dimensional image. The present invention can be configured in one of several ways to yield the data required by a computer to produce a three dimensional image of a semi opaque object such as a leg, foot, breast, or tooth, and to detect anomalies therein. Furthermore, the present invention drastically reduces the size of the imaging equipment and reduces the time required to make images.
Articles which demonstrate the utility of transillumination in biological and medical applications include: Wist et al.,
IEEE Transactions on Medical Imaging
, Vol. 12, No. 4, December, 1993 (pages 751-757); Wist et al.,
J Clin. Laser Med. In Surgery,
11:313-321 (1993); Wist et al.,
J. Clin Laser Med. In Surgery,
12:165-170 (1994); Swineford et al.,
Proceedings of Clinical Applications of Modern Imaging Technology II, SPIE
, Vol. 2132, pp.201-207 (1994); Wist,
SPIE
2628:286-299 (1995); and Wist et al.,
SPIE
, 2389-552-563. These articles show the use of transillumination scanning technology in detecting incipient caries in teeth and identifying objects in tissues.
SUMMARY OF THE INVENTION
It is an object of this invention to provide transillumination instrumentation and methods which provide for improved object detection in biological samples, and which are of a compact size.
Another object of this invention is to provide a mechanism for quickly processing sensed transillumination signals over a very large signal range.
Another object of this invention is to provide a method for matching a discriminating plate to a laser and detector array combination.
Another object of this invention is to provide transillumination instrumentation that have specific applications in imaging teeth.
Another object of this invention is to provide methods using transillumination for creating three dimensional images.
Another object of this invention is to provide a method for creating an accurate transillumination image using a single light source.
Another object of this invention is to use the laser speckle effect to produce transillumination images.
According to the invention, an array of diodes is placed on one side of a semi opaque object and the light passing through the object is received by an array of detectors. The diodes may be lit sequentially or coded and lit all at once, the character of light received at each of the detectors is analyzed to determine if abnormalities are present. The light received by the detectors is essentially a cross-sectional image of the examined semi opaque object. Light passing through the semi opaque object may be deflected causing stray light beams which will result in a distorted image of the object or any anomaly found therein or result in missing an anomaly altogether. To improve image quality and detection ability a mechanical discriminator in the form of a substrate is placed in front of the detector array. The mechanical discriminator contains a plurality of optical passages each aligned with detectors behind the substrate. The optical passages allow only perpendicular light beams to traverse the substrate to the detector. Stray light beams are excluded by the walls of the optical passages. The optical passages are 1-100 &mgr;m in diameter and 100-10,000 &mgr;m in length and normally have a diameter to length ratio of 1/100. The optical passage walls may be roughened to further absorb any stray light which might strike the optical passage walls. When light emitted from an array is passed through an object of study and detected on the opposite side by a detector array it is said that one scan has been completed.
In a variation of the invention, a single light source can be used to produce an accurate two dimensional transillumination image by positioning a light discriminator, equipped with optical passages that are not parallel to each other, between a light source and a detector array. A single light source for providing non-collimated light will produce a fan type beam of light. Optical passages are provided in the mechanical discriminator that will allow only light radially emitted from the light source to pass through and strike the detector array. When a semi opaque object is placed between the light source and the detector array, set at a predetermined distance apart, some light passing through the object will be deflected causing stray light, however; only light traveling radially outward from the light source straight through the object will traverse the discriminator via an optical passage. This configuration is easily set up and less costly than others; however, a predetermined distance must be maintained between the light source and the discriminator and detector. This configuration is particularly well suited for imaging teeth because the light source can be pl
Lateef Marvin M.
Lin Jeoyuh
McGuireWoods LLP
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