Dentistry – Apparatus – Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
2000-09-12
2002-07-16
Manahan, Todd E. (Department: 3732)
Dentistry
Apparatus
Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
active
06419484
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to dental drills, particularly to improved dental drills having vicinity imaging capability and, more particularly, to dental drills provided with optical fibers connected to an optical coherence domain reflectometry (OCDR) to image several millimeters ahead of the ablation surface.
In dentistry, drills are used to remove cavities and to prepare for restoration and implants. In many cases it would be valuable to image below the surface being drilled to minimize damage to vital normal tissue. Identifying the boundary between decayed and normal enamel (or dentine) would reduce the removal of viable tissue; and identifying the nerve before getting too close with the drill could prevent nerve damage. Thus, there is a need for dental treatment imaging, and such has been accomplished by the present invention using (OCDR).
Optical coherence domain reflectometry is a technique developed by Youngquist et al. in 1987 (Youngquist, R. C. et al., “Optical Coherence-Domain Reflectometry: A New Optical Evaluation Technique,” 1987,
Optics Letters
12(3): 158-160). Danielson et al. (Danielson, B. L. et al., “Guided-Wave Reflectometry with Micrometer Resolution,” 1987,
Applied Physics
26(14): 2836-2842) also describe an optical reflectometer which uses a scanning Michelson interferometer in conjunction with a broadband illuminating source and cross-correlation detection. OCDR was first applied to the diagnosis of biological tissue by Clivaz et al. in January 1992 (Clivaz, X. et al., “High-Resolution Reflectometry in Biological Tissues,” 1992,
Optics Letters
17(1): 4-6). A similar technique, optical coherence tomography (OCT) has been developed and used for imaging with catheters by Swanson et al. in 1994 (Swanson, E. A. et al., U.S. Pat. Nos. 5,321,501 and 5,459,570. Tearney et al. (Tearney, G. J. et al., “Scanning Single-Mode Fiber Optic Catheter-Endoscope for Optical Coherence Tomograph,” 1996,
Optics Letters
21(7): 543-545) also describe an OCT system in which a beam is scanned in a circumferential pattern to produce an image of internal organs. U.S. Pat. No. 5,570,182 to Nathel et al. describes method and apparatus for detection of dental caries and periodontal disease using OCT. However, as OCT systems rely on mechanical scanning arms, miniaturizing them enough to operate on a guidewire would be very difficult.
Polarization effects in an OCDR system for birefringence characterization have been described by Hee et al. (Hee, M. R. et al., “Polarization-sensitive low-coherence reflectometer for birefringence characterization and ranging,”
J. Opt. Soc. Am.
B, Vol. 9, No. 6, June 1992, 903-908, and in an OCT system by Everett et al. (Everett, M. J. et al., “Birefringence characterization of biological tissue by use of optical coherence tomography,”
Optics Letters
, Vol. 23, No. 3, Feb. 1, 1998, 228-230).
In a prior art OCDR scanning system
10
, shown in
FIG. 1
, light from a low coherence source
12
is input into a 2×2 fiber optic coupler
14
, where the light is split and directed into sample arm
16
and reference arm
18
. An optical fiber
20
is connected to the sample arm
16
and extends into a device
22
, which scans an object
24
. Reference arm
18
provides a variable optical delay. Light input into reference arm
18
is reflected back by reference mirror
26
. A piezoelectric modulator
28
may be included in reference arm
18
with a fixed mirror
26
, or modulator
28
may be eliminated by scanning mirror
26
in the Z-direction. The reflected reference beam from reference arm
18
and a reflected sample beam from sample arm
16
pass back through coupler
14
to detector
30
(including processing electronics), which processes the signals by techniques that are well known in the art to produce back-scatter profile (or “image”) on display
32
.
The present invention utilizes a drill surrounded with several optical fibers used by an OCDR to image several millimeters ahead of the ablation surface. The OCDR system translates this information into a profile image of the tissue optical properties near the ablation surface. This information can be displayed to the user, or analyzed by software to sound an alarm, or stop the drill when a selected boundary or distance to sensitive tissue, nerve, blood vessel, etc., is reached.
SUMMARY OF THE INVENTION
It is an object of the present invention to enable improved dental drilling procedures.
A further object of the invention is to provide imaging of areas slightly ahead of the ablation area of dental drilling.
A further object of the invention is to provide a method for obtaining images of areas ahead of the ablation area.
It is a further object of the invention to utilize OCDR in combination with a dental drill to enable imaging of areas adjacent the drilling operation.
Another object of the invention is to provide a dental drill with optical fibers connected to an OCDR to enable imaging of areas ahead of the drilling or ablation area.
Another object of the invention is to provide an improved dental drilling system, which includes imaging by the user of the area to be drilled, and to provide an alarm or to stop the drill when a selected boundary or distance from the drilling operation is reached.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. Basically, the invention involves an optical coherence tomography (OCT) guided dental drill. The invention is a dental drill that has one or multiple single-mode fibers that can be used to image in the vicinity of the drill tip. Identifying the boundary between decayed and normal enamel (or dentine) reduces the removal of viable tissue, and identifying the nerve before getting too close with the drill prevents nerve damage. The drill is surrounded with 1, 2,4 or more single-mode optical fibers, which independently couple light from a sample arm of an OCDR system to the tissue to be removed. Light from these OCDR fibers exit the tip and are directed into the hard or soft tissue via small diameter optics (such as gradient index lenses and prisms). The light reflected or scattered from the tissue is then collected by the same optical fibers and detected by the OCDR system, which translates this information into a profile image of the tissue optical properties near the ablation surface. This information can be displayed to the user or analyzed by software to sound an alarm or stop the drill when a selected boundary or distance to sensitive tissue is reached. The invention can use single or multiple OCDR systems (one for each imaging fiber), or can be used with a form of multiplexing.
REFERENCES:
patent: 5049070 (1991-09-01), Ademovic
patent: 5178536 (1993-01-01), Werly et al.
patent: 5290168 (1994-03-01), Cooper et al.
patent: 5321501 (1994-06-01), Swanson et al.
patent: 5459570 (1995-10-01), Swanson et al.
patent: 5570182 (1996-10-01), Nathel et al.
patent: 5634790 (1997-06-01), Pathmanabham
patent: 5894620 (1999-04-01), Polaert et al.
patent: 6179611 (2001-01-01), Evert et al.
B.L. Danielson et al, Guided-Wave Reflectometry with Micrometer Resolution, Applied Optics, vol. 26, No. 14, Jul. 15, 1987.
M.J. Everett et al, Birefringence Characterization of Biological Tissue by Use of Optical Coherence Tomography, Optics Letters, vol. 23, No. 3, Feb. 1, 1988.
R.C. Youngquist et al, Optical Coherence-Domain Reflectometry: A New Optical Evaluation Technique, Optical Letters, vol. 12, No. 3, Mar. 1987.
X. Clivaz et al, High-Resolution Reflectometry in Biological Tissues, Optics Letters, vol. 17, No. 1, Jan. 1, 1992.
M.R. Hee et al, Polarization-Sensitive Low-Coherence Reflectometer for Birefringence Characterization and Ranging, J.Opt.Soc.Am.B.,vol. 9, No. 6, Jun. 1992.
G.J. Tearney et al, Scanning Single-Mode Fiber Optic Catheter-Endoscope for Optical Coherence Tomography, Optics Letters, vol. 21, No. 7, Apr. 1996.
Colston, Jr. Bill W.
DaSilva Luiz B.
James Dale L.
Carnahan L. E.
Manahan Todd #E.
The Regents of the University of California
Thompson Alan H.
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