U.S. patent application number 13/187106 was filed with the patent office on 2011-11-10 for spectrally encoded miniature endoscopic imaging probe.
This patent application is currently assigned to The General Hospital Corporation. Invention is credited to Brett Eugene Bouma, Jonathan Jay Rosen, Milen Stefanov Shishkov, Guillermo J. Tearney.
Application Number | 20110275899 13/187106 |
Document ID | / |
Family ID | 24848726 |
Filed Date | 2011-11-10 |
United States Patent
Application |
20110275899 |
Kind Code |
A1 |
Tearney; Guillermo J. ; et
al. |
November 10, 2011 |
SPECTRALLY ENCODED MINIATURE ENDOSCOPIC IMAGING PROBE
Abstract
A spectrally encoded endoscopic probe having high resolution and
small diameter comprising at least one flexible optical fiber; an
energy source; a grating through which said energy is transmitted
such that the energy spectrum is dispersed; a lens for focusing the
dispersed energy spectrum onto a sample such that the impingement
spot for each wavelength is a separate position on the sample, the
wavelength spectrum defining a wavelength encoded axis; means for
mechanically scanning the sample with focused energy in a direction
perpendicular to the wavelength encoded axis; a means for receiving
energy reflected from the sample; and, a means for detecting the
received reflected energy. The probe grating and lens delivers a
beam of multi-spectral light having spectral components extending
in one dimension across a target region and which is moved to scan
in another direction. The reflected spectrum is measured to provide
two dimensional imaging of the region.
Inventors: |
Tearney; Guillermo J.;
(Cambridge, MA) ; Bouma; Brett Eugene; (Quincy,
MA) ; Shishkov; Milen Stefanov; (Boston, MA) ;
Rosen; Jonathan Jay; (Newton, MA) |
Assignee: |
The General Hospital
Corporation
Boston
MA
|
Family ID: |
24848726 |
Appl. No.: |
13/187106 |
Filed: |
July 20, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09709162 |
Nov 10, 2000 |
|
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13187106 |
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Current U.S.
Class: |
600/160 |
Current CPC
Class: |
A61B 1/0017 20130101;
A61B 1/043 20130101; A61B 5/0084 20130101; A61B 5/0071 20130101;
A61B 5/0059 20130101; A61B 1/00096 20130101; A61B 1/07 20130101;
A61B 5/0062 20130101; G02B 21/0064 20130101; G02B 21/0048 20130101;
G02B 21/0036 20130101 |
Class at
Publication: |
600/160 |
International
Class: |
A61B 1/06 20060101
A61B001/06 |
Claims
1-67. (canceled)
68. An apparatus, comprising: at least one arrangement which
includes at least one of an optical fiber or an optical waveguide,
and which is provided to illuminate a structure with at least one
electro-magnetic radiation, the at least one arrangement including:
a. at least one core region through which a first radiation of at
least one electromagnetic radiation is transmitted to the
structure, b. at least one cladding through which a second
radiation of the at least one electromagnetic radiation is received
from the structure, wherein the first and second radiations are at
least partially different from one another, and c. at least one
wavelength dispersive arrangement which is configured to disperse
at least one of the first radiation or the second radiation.
69. The apparatus according to claim 68, wherein the structure
includes a tissue.
70. The apparatus according to claim 68, wherein the at least one
arrangement in a confocal arrangement.
71. The apparatus according to claim 68, further comprising at
least one further arrangement which is configured to receive
signals from the at least one cladding, and generate at least one
image of the structure based on the signals.
72. The apparatus according to claim 68, wherein the at least one
wavelength dispersive arrangement is provided in a radiation path
between the structure and at least one of the core or the
cladding.
73. The apparatus according to claim 68, wherein the at least one
wavelength dispersive arrangement is provided in a radiation path
between the structure and at least one of the core or the
cladding.
74. The apparatus according to claim 68, wherein the at least one
core region is configured to receive therethrough the second
radiation.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of endoscopy in
general and to an endoscope having a combination of high number of
resolvable points using spectral encoding and contained in a
diameter/space small enough to perform desired procedures.
BACKGROUND OF THE INVENTION
[0002] Clinical use of endoscopic devices and probes has permitted
physicians to view and diagnose target bodies, such as tumors,
deposits, tears, thrombi, and the like. Unfortunately, there are
still a number of disadvantages and limitations of using
conventionally available endoscopes. The diameter of currently
available probes limits their use to certain procedures and
locations that can accommodate the large diameter of the endoscope.
Consequently, many procedures currently done surgically could be
done endoscopically, if a small enough probe was available with a
sufficient number of resolvable points.
[0003] Current endoscopic procedures generally require
administration of anesthesia and surgical training for insertion.
Certain procedures cannot currently be done endoscopically because
of the diameter of existing probes. Probe size is proportional to
the likelihood of tissue damage occurring during the procedure.
Another problem associated with current probes is the occurrence of
adverse reactions, such as in fetoscopy, where the risk to the
fetus is high. Neural imaging carries with it the possibility of
brain damage. Spinal canal and brain ventricular imaging have
complications of spinal fluid leakage and headaches which are more
frequent and severe with larger diameter probes. Catheterization of
the pancreatic duct is also problematic due to the probe size and
resultant complications which include acute pancreatitis. Also, the
size of the incision necessary to insert current probes results in
longer healing time and more prominent scarring.
[0004] Present day miniature endoscopes are composed of fiber-optic
imaging bundles. Currently, the clinical use of small diameter
endoscopes is limited by poor resolution. Available miniature
endoscopes have diameters in the range of from about 0.35 mm to
about 1.0 mm. Since optical fibers are of finite diameter, only a
limited number of fibers can be incorporated into one imaging
bundle, resulting in a limited number of resolvable elements. For
example, for a 1 mm fiber optic imaging bundle with an individual
fiber diameter of 10 .mu.m, the total number of resolvable points
is 9000 with 100 resolvable points across the field of view. In
addition, the fill factor is about 85% resulting dead space from
the cladding material and causing the image to have a pixelated or
"honeycomb" appearance. These two technical problems have severely
limited the clinical use of currently available sub-millimeter
diameter imaging probes. In order to achieve a higher number of
resolvable elements with such probes, larger diameters must be
used, which obviate their use in smaller spaces and eliminate
certain procedures from being done endoscopically. If one uses a
currently available probe in the sub-millimeter diameter range, the
number of resolvable points obtainable drops below clinically
useful levels. Present endoscopes have a light transmission
efficiency of up to about 50%.
[0005] A further disadvantage of fiber bundles is that crosstalk
occurs, reducing the signal to noise level. Moreover, as fiber
length increases, light transmission efficiency decreases. Also
with current fiber optic endoscopes, coupling illumination light
into the fiber optic imaging bundle is difficult. As a result,
miniature endoscopes need two separate fiber bundles, one for
illumination and one for detection of the image. The need for
distinct illumination and detection bundles increases (at least
doubles) the overall endoscope diameter. It would therefore be
desirable to have a long length endoscope probe that retains
sufficient light transmission efficiency to provide a clinically
useful image and information.
[0006] Another disadvantage of optical fiber bundles is that
individual fibers may be broken or have defects at their faces,
resulting in "dead" pixels. The use of one fiber would greatly
minimize the presence of dead pixels.
[0007] Thus, it would be desirable to have a probe that provided a
satisfactory number of resolvable elements in a space/diameter
below a certain size that would enable procedures to be done
currently not achievable by currently available endoscopes. It
would be desirable to have a probe in the sub-millimeter diameter
range that had optics that would improve the number of resolvable
points, reduce deadspace/fill factor, and minimize risk of adverse
consequences to the patient. Such a novel probe would enable
procedures to be performable that currently cannot be attempted
endoscopically, such as, but not limited to, otological, neural,
pancreatic, and fetal surgical endoscopy. It would also be
desirable to have a sub-millimeter endoscope that would allow for
diagnosis as well as treatment in a single device.
[0008] Spectral encoding is a method that allows detection of a
one-dimensional line of an image using a single optical fiber.
Encoding the spatial information on the sample is accomplished by
using a broad bandwidth source as the input to the endoscope. The
source spectrum is dispersed by a grating and focused by a lens
onto the sample. The spot for each wavelength is then focused at a
separate position, x, on the sample. The reflectance as a function
of transverse location is determined by measuring the reflected
spectrum. The other dimension of the image can be obtained by
mechanical scanning at a slower rate. The advantage of this mode of
imaging is that the fast scanning needed to produce an image at or
near video frame rates is performed externally to the probe, making
the construction of small diameter probes feasible.
SUMMARY OF THE INVENTION
[0009] The present invention discloses a miniature imaging probe or
endoscope that is capable of obtaining real-time images with up to
or higher than about 100 times the number of resolvable points than
a fiber-optic imaging bundle of the same diameter. Another way of
describing the present invention is for the same number of
resolvable pixels as commercially available imaging bundles, the
present invention could have a diameter that is 10 times smaller.
In addition, this instrument produces images that do not contain
cladding artifacts. Also, this invention allows acquisition of
depth (three-dimensional, or 3D) information from the sample.
Finally, by acquiring multiple images of the sample, spectroscopic
information relating to the chemical composition of the object may
be obtained. These properties make this device an enabling
technology for performing endoscopic or catheter based imaging in
previously inaccessible locations within the body. Important
specific applications include fetoscopy, pediatric endoscopy,
coronary angioscopy, mini-laparoscopy, mammary ductoscopy, lacrimal
ductoscopy, small joint visualization, and other medical and
non-medical applications.
[0010] Significant work related to this invention is described in
copending application Ser. No. 60/076,041, filed Feb. 26, 1998
(corresponding to regular application, Ser. No. ______, filed
______, and International Application Serial No. PCT/US99/04356,
filed Feb. 26, 1999), entitled Confocal Microscopy With
Multi-Spectral Encoding, the disclosures of which are incorporated
herein in their entirety. This prior disclosure described the use
of spectral encoding to perform endoscopic confocal microscopy. The
present invention describes the use of spectral encoding to create
small diameter endoscopes and obtain high-resolution macroscopic
images. The present invention includes different embodiments and
applications of spectral encoding for performing endoscopic imaging
through small diameter probes.
OBJECTS OF THE INVENTION
[0011] Accordingly, it is a principal object of the present
invention to provide an endoscope having a combination of
resolution above a certain level in a diameter or space below a
certain size.
[0012] It is an object of the present invention to provide an
endoscope having a combination of number of resolvable elements
above about 10,000 in a space below about 1.0 mm.sup.2.
[0013] It is another object of the present invention to provide an
endoscope in the generally sub-millimeter diameter range that
increases the number of resolvable elements.
[0014] It is also an object of the present invention to provide an
endoscope that can be used in smaller spaces than currently
available endoscopes.
[0015] It is another object of the present invention to provide an
endoscope that can be used in conjunction with a small diameter
needle so as to avoid anesthesia and where the endoscopic procedure
can be done, where appropriate, on an outpatient basis.
[0016] It is another object of this invention to provide an
endoscope which is simpler to manufacture and is less likely of
having individual pixel defects than current fiber optic
bundles.
[0017] It is a further object of the present invention to provide
an endoscope using spectral encoding and using a single fiber.
[0018] It is yet another object of the present invention to provide
an endoscope capable of obtaining spectroscopic information from
the sample.
[0019] It is a further object of the present invention to provide a
third dimension of information (depth), above the typical two
dimensions of data obtainable from conventional endoscopes.
[0020] It is yet another object of the present invention to provide
higher sensitivity and higher signal to noise ratio images for
clearer visualization through turbid media.
[0021] It is still another object of the present invention to
provide an endoscope that can reduce the likelihood of tissue
damage and other adverse consequences.
[0022] It is another object of the present invention to provide an
endoscope that allows for diagnosis and treatment in a single
procedure.
[0023] It is yet a further object of the present invention to
provide an endoscope having no fill factor problem.
[0024] It is yet another object of the present invention to provide
an endoscope with no "dead" pixels.
[0025] Other objects, features and advantages of the present
invention will become apparent upon reading the following detailed
description of embodiments of the invention, when taken in
conjunction with the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention is illustrated in the drawings in which like
reference characters designate the same or similar parts throughout
the figures of which:
[0027] FIG. 1 is a schematic view of a spectrally encoded miniature
camera according to a preferred embodiment of the present
invention.
[0028] FIGS. 2A-F are schematic views of different possible
configurations of the distal probe of the camera of FIG. 1.
[0029] FIGS. 3A-C are schematic views of the image formation
geometry for linear, sector and circular scans, respectively.
[0030] FIG. 4 is a schematic view of a preferred embodiment of the
detection system of the camera of FIG. 1.
[0031] FIG. 5 is a schematic view of an alternative embodiment of
the present invention showing a color spectrally encoded miniature
camera.
[0032] FIG. 6 is a schematic view of an alternative embodiment of
the present invention showing a multifiber array incorporating a
plurality of grating lenses.
[0033] FIG. 7 is a schematic view of an alternative embodiment of
the present invention showing an optical fiber having spaced lenses
along its length.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] The present invention provides in general an endoscopic
probe having a small diameter and a high number of resolvable
elements. For the purposes of the present disclosure, a probe
diameter in the sub-millimeter range is most desirable; however, it
is to be understood that diameters of or greater than 1 mm can be
used with the present invention. The advantages of the resolution
of the present invention certainly carry to probes with greater
than 1 mm diameter. Thus, the present invention provides a
combination of number of resolvable points above a certain level in
a diameter or space below a certain level.
[0035] FIG. 1 shows an endoscope 10 of a preferred embodiment
consisting of main body 12 connected through a hybrid (optical and
electrical) cable 14 to a probe 16. The cable 14 can instead be a
discontinuity conducted across a gap (for example, optical,
electrical or electromagnetic relay), discussed hereinbelow with
respect to an alternative embodiment using a self-contained probe
with a transmitter to a remote receiver/detector. The main body 12
incorporates a broadband source 18 that sends the illuminating
light to the beam-redirecting element 20. In different designs this
beam-redirecting element 20 can be a beam splitter (simple,
inexpensive, but poor light efficiency), a polarizing splitter, an
optical circulator or other device known to those skilled in the
art. This beam-redirecting element 20 sends out the light from the
source 18 to the probe 16 and redirects the returning light from
the probe 16 to the detection and display system 22. The detection
system is preferably associated with a computer with a
microprocessor (not shown).
[0036] The probe 16 has three major components. The proximal end 24
generates the one-dimensional scanning. In a preferred embodiment
the scanning is done mechanically. A flexible, semi-flexible or
rigid tube 26 connects the proximal end 24 and the distal end 28 of
the imaging probe 16. An optical fiber conveys the optical signals
and a hollow flexible, semi-flexible, or rigid cable conveys
one-dimensional scanning of the sample 30.
[0037] The cable 14 is preferably a single mode optical fiber.
Another embodiment is a double-clad fiber where the illumination is
through the central core and the detection is through the central
core and outer cladding. Alternatively, the cable 14 can be a
co-axial or side-by-side pair of fibers, with one fiber being for
illumination by the source and the other fiber being for collection
of light reflected from the sample 30. In a device where a
multimode fiber system is used, there may be increased sensitivity
and decreased speckling. Speckle artifacts may also be reduced by
introducing mode or phase modulation of the fiber. Mode or phase
modulation may be performed by rapidly moving the optical fiber, or
insertion of an optical element in the fiber path capable of
rapidly changing modes or phase of the probe light. This embodiment
includes the detection mechanism within the probe and a RF
transducer to relay image information remotely to a RF
detector).
Sources
[0038] The light source 18 can be any broadband source capable of
performing high-resolution imaging using the spectral encoding
method. Examples of sources include, but are not limited to,
light-emitting diodes, super-luminescent diodes, rare-earth doped
fibers, solid-state mode-locked lasers, spectrally broadened laser
sources, wavelength tunable light sources, monochromatic light,
polychromatic light, and the like. The source 18 does not need to
illuminate all wavelengths simultaneously. It can emit a
monochromatic radiation whose wavelength is scanned with time. This
allows fluorescence illumination to be done. It also does not
require Fourier transform to be done. It is to be understood that
other sources of energy can be used, including, but not limited to,
infrared, ultraviolet, ultrasonic, low or high energy radiation
(for example, x-ray, alpha, beta, gamma, and the like), other
electromagnetic radiation, combinations of all of the foregoing and
the like. For higher energy radiation, certain of the components of
the present invention may need to be adapted for greater shielding
or other functional characteristics.
Distal Probe Design
[0039] The distal probe 16 design of the present invention will now
be discussed. FIG. 2 shows several possible configurations of the
imaging head 28. The optics of the head 28 is designed to produce
linear, spectrally encoded illumination and to collect the
reflected light and transmit it back to the detection system 22.
The light from the source 18 is delivered by the fiber 14 to the
head 16 and focused by an objective 32 onto the sample 30. In a
preferred embodiment the objective 32 is a lens, for example, but
not by way of limitation, a GRIN (gradient index) lens, as is known
to those skilled in the art. Other possible lens elements include,
but are not limited to aspherical lenses, planoconcave, biconcave,
concaveconvex or multi-element lens assemblies.
[0040] Immediately after (or before) the objective 32, a grating 34
is used to disperse the source spectrum. In a preferred embodiment,
shown in FIG. 2A, the grating 34 is a holographic grating.
Alternatively, blazed or binary gratings or a grism (grating prism
or carpenter's prism) can be used. Holographic gratings, however,
are believed to be better and have higher efficiency than blazed
gratings for the intended use. Fiber gratings may also be used. The
spot for each wavelength is focused at a separate position on the
sample. The reflectance as a function of transverse location is
determined by measuring the reflected spectrum. The head 16 also
provides one-dimensional mechanical scanning orthogonal (or other
angle) to the spectrally encoded axis. Spectral dispersion in one
dimension while scanning the other dimension provides
two-dimensional illumination of the sample.
[0041] FIGS. 2B-F illustrate alternative embodiments of the probe
16 design of FIG. 2A. On the Figures the elements are: optical
fiber 14; imaging head 16; objective 32; diffracting grating 34
(FIGS. 2A and 2D show a transmission grating, FIGS. 2B, C and E
show a reflecting grating 36, and FIG. 2F shows a fiber 38); a beam
stop 40; a spectrally encoded imaging line 42; a mirror 44; a beam
splitter 46; a polarizer 48; a polarizing beam splitting cube 50;
and a 1/4 wavelength plate.
[0042] Image formation will now be discussed. The use of the
dispersing element 34 and the focusing of the spectrum on the
sample 30 to be imaged produces a one-dimensional scan. In order to
obtain a two-dimensional image, one must perform a transverse scan
in the conjugate direction. This can be implemented in many
different embodiments, but all include a means of moving the
spectrally encoded scan line. In a preferred embodiment the
movement is achieved mechanically. Several possible methods for
one-dimensional mechanical scanning are shown in FIGS. 3 A-D. It is
possible to use a piezoelectric transducer or a torque-transducing
device known to those skilled in the art to achieve movement. The
probe body 12 is associated with a transparent cap 60. A flexible
cable 62 carries the fiber 14. The optical head 28 and the
spectrally encoded imaging line 64 are shown. The two-dimensional
imaging region is shown at 66. FIG. 3A shows a linear scan; FIG. 3B
shows a sector scan; FIG. 3C shows a circular scan; and, FIG. 3D
shows a forward circular scan. This may be performed by use of a
rotating or linearly translating cable where the motion is produced
at the proximal end of the endoscope. One can either rotate the
optical head or push it linearly forth and back, moving the imaging
line on the sample and scanning the image. The fiber may also be
moved as opposed to the distal optics to give the alternate
scan.
[0043] The proximal probe end design and coupling mechanisms will
now be discussed. Referring back to FIG. 3, the proximal end 24 of
the probe 16 provides the mechanical scanning necessary for
obtaining a two dimensional image. In addition, this end couples
the light coming from the source 18 to the distal end 28 of the
probe 12 and the optical signal coming back from the sample 30.
Linear (axial or radial), sector, or circumferential scanning
patterns are possible depending on the application. For example, in
narrow vessel imaging, such as angioscopy, circumferential scanning
is necessary to image the total surface of the vessel. In this case
a special rotating junction must be incorporated into the proximal
end 24 of the probe 16 to connect optically a stationary and a
rotating fiber 14. For sector and linear scanning, the optical
fiberl 4 within the probe 16 may be directly fused to the
beam-redirecting element 20. The preferred scanning embodiment is
sector or circumferential scanning due to the availability of small
diameter cables already constructed for this purpose.
Resolution
[0044] The number of wavelengths or points that may be resolved is
determined by:
.lamda. .differential. .lamda. = m N , ( 1 ) ##EQU00001##
where .lamda. is the center wavelength, .differential..lamda. is
the bandwidth of the spectrum, N is the number of lines in the
grating illuminated by the polychromatic input beam, and m is the
diff action order. If the total bandwidth of the source is
.DELTA..lamda., the number of resolvable points, n is defined
by:
n = .DELTA..lamda. .differential. .lamda. . ( 2 ) ##EQU00002##
[0045] For an input source with a center wavelength of 1000 nm, a
bandwidth of 200 nm, an input spot diameter of 1 mm, a diffraction
grating of 1200 lines/mm and a diffraction order of 1, n=240 points
may be resolved by the spectrally encoded system. Moreover, if the
grating is at an angle (.theta.) with respect to the incoming
light, the number of resolvable points scales with 1/cos(.theta.).
In the above example, for an incident angle of 65.degree., the
number of resolvable points would be approximately n=570. If the
perpendicular direction was also scanned to give 570 points of
resolution, the total number of resolvable points would be
approximately 320,000. This is compared to 10,000 resolvable points
(n=about 80) found in state of the art single mode fiber bundles
with a diameter of 1 min. Thus, the present invention can provide
approximately 16 times better resolution than conventional fiber
optic probes.
[0046] The parameters used in this example may be found in common,
inexpensive optical components. The number of points may be
increased by simply increasing the input angle or the bandwidth of
the source 18. Increasing the spot diameter increases the resultant
probe diameter. Increasing the bandwidth of the source 18 could be
accomplished by using a broader bandwidth superluminescent diode, a
broad bandwidth LED, a rare earth doped fiber superfluorescent
source, a solid state modelocked laser, a continuum source or the
like.
[0047] Practitioners in endoscopic procedures would generally agree
that a minimum number of resolvable elements of about
256.times.256=65,536 is needed to do meaningful diagnostic
procedures. This is based on the fact that this is approximately
the current accepted standard used in laparoscopic procedures.
Current high end endoscopes have an upper end of about 10,000
elements in about a 1 mm diameter probe. Currently also, there are
several fiber bundles that have 30,000 elements in about a 1 mm
probe, but they are not yet in clinical use due to technical
limitations.
[0048] The device of the present invention provides, in a preferred
embodiment, a probe having a diameter of about 1.0 min with a
number of resolvable points in the range, in its broadest aspect,
of from about 10,000 to about 1,000,000 resolvable points, more
preferably, of from about 300,000 to about 1,000,000 resolvable
points, more preferably of from about 150,000 to about 300,000
resolvable points, and still more preferably of from about 100,000
to about 150,000 resolvable points. The number of resolvable points
roughly scales with diameter. It is to be understood by those
skilled in the art that other diameters can be used with
correspondingly greater or lesser numbers of resolvable points.
[0049] Table 1 provides a comparison of the number of resolvable
elements using a spectrally encoded endoscope ("SEE") of the
present invention compared to that using conventional fiber optic
bundles. For the SEE, .DELTA..lamda. (bandwidth) 250 nm, .LAMBDA.
(grating density) 1200 lines per mm.
TABLE-US-00001 TABLE 1 Number of resolvable elements Diameter (mm)
Fiber Bundle Spectral Encoded Endoscope 1.0 10000 160000 0.7 5000
80000 0.5 2500 40000 0.25 625 10000
Energy Budget
[0050] The intensity I of the returned light in a Michelson
interferometer configuration of the camera is given by
I = 1 8 .gamma. 1 2 .gamma. 2 d 2 .rho..PHI. b 2 N I 0 , ( 3 )
##EQU00003##
where I.sub.0 is the source intensity, .gamma..sub.1 and
.gamma..sub.2 are the diffracting efficiencies of the imaging and
detecting grating, d is the beam diameter at the objective, .rho.
is the reflectivity of the surface to be imaged (spectral and
location dependent), .phi. is a detector filling factor, and N is
the number of the points to be detected.
[0051] The attenuation of the signal in dB .epsilon. is then given
by
= 10 log I I 0 = 10 log [ 1 8 .gamma. 1 2 .gamma. 2 d 2 .rho..PHI.
b 2 N ] ( 4 ) ##EQU00004##
[0052] In this formula different contributions can be considered as
follows
= 10 log 1 8 + 10 log G + 10 log .GAMMA. + 10 log .rho. + 10 log D
, ( 5 ) ##EQU00005##
where g=.gamma..sub.1.sup.2.gamma..sub.2 is the diffracting
efficiency factor,
.GAMMA. = d 2 b 2 ##EQU00006##
is the numerical aperture factor, assuming a Lambertian reflector,
and
D = .PHI. N ##EQU00007##
is detection system related factor. For typical values of standard
grating efficiencies and numerical apertures used in this device,
the total attenuation would be approximately 60 dB. This number can
be significantly improved by using custom designed diffraction
gratings.
[0053] Detection will now be discussed.
Direct Spectral Measurement
[0054] The reflectance from the sample as a function of transverse
location is determined by measuring the reflected spectrum from the
sample arm. A simple and efficient direct measurement system 70 is
shown in FIG. 4, in which an enclosure 71 houses the system 70
components.
[0055] The light returning from the imaging position carried by the
fiber 14 is collimated by the objective 72 and dispersed by the
grating 34. The scanning mechanism 72 is synchronized with the
probe scanning mechanism or (in a compact design) the same scanning
mechanism can be used to scan the probe and the detection system.
This allows direct imaging using a camera 74, such as, but not
limited to, a standard, inexpensive CCD camera that attaches to the
detection system housing. An intensified CCD camera (ICCD) can be
used when/if the signal is too weak. Electronic scanning with
computer aided imaging can be implemented if a linear array is used
as a detector. In this case no moving parts are necessary in the
detection system 70 and higher detector sensitivity can be
achieved. The detection system 70 can be either a single detector
70, a one dimensional array of detectors 70, or a two dimensional
array of detectors 70. Other camera types and other detectors known
to those skilled in the art are contemplated as being within the
scope of the present invention.
[0056] For low light applications, the spectrum may be measured
more efficiently by incorporating the device in the sample arm of
an interferometer and detecting the light transmitted through a
high-resolution spectrometer at the output port of the
interferometer. Higher sensitivity may be achieved through the use
of heterodyne detection when the light in the reference arm is
modulated. The signal detected at the interferometer output will
also be modulated. High signal-to-noise ratios may be then achieved
by lock-in detection on the reference arm modulation frequency.
Interference Spectroscopy
[0057] Another method for measuring the spectrum is interference
spectroscopy or Fourier transform spectroscopy. The advantages to
this type of spectroscopic detection include the ability to achieve
higher spectral resolutions than direct detection methods,
efficient use of the returned light, inherent modulation of the
reference arm by the Doppler shift of the moving mirror, the
possibility of obtaining three-dimensional information, and the
capability to extract both reflectance and phase data from the
sample. The ability to extract phase data from the sample may allow
detection of refractive index as a function of transverse position,
which could give insight into the molecular composition of the
sample as well as provide an additional source of image contrast
other than the reflectivity of the specimen. Also, interferometric
detection has the potential to allow elimination of high order
multiple scattering from the signal by coherence gating. Moreover,
analysis of both the phase and amplitude of the interferometric
signal allows detection of group delay and dispersion. In most
cases, knowledge of the group delay gives information relating the
distance of the probe to the object under inspection and dispersion
provides information about the shape of the object under
inspection. Finally, mechanical scanning may be eliminated if
points on the object, perpendicular to the spectrally encoded axis,
may be separated by coherence gating.
Color Embodiment
[0058] In an alternative embodiment of the present invention, shown
in FIG. 5, a device 100 can be constructed that uses at least two
and preferably three or more separate broadband source modules 110,
for example, three sources centered at red (630 nm) 102, green (540
nm) 104, and blue (480 nm) 106 to produce color images using this
technique. It is to be understood that other colors, wavelengths
and number of separate sources can be selected depending on various
factors, including, but not limited to, the imaging environment,
imaging target, measurements to be obtained, and the like. The
three energy components can be separated after reflection from the
sample 30 and recombined to form an image. Each of the
source/detector modules 102, 104 and 106 for the three spectral
bands transmits selected wavelength light to an optical
mixer/separator 108, which selectively transmits the light toward
the imaging head 109 and to the imaging optics 110 for the
different colors. The light reflects off of the sample/imaging
plane 112 back through the foregoing elements and is received by a
color monitor 114.
[0059] One use of this embodiment is for illuminating a stained
sample with one color light and detecting the reflected or
retransmitted light which may be of a different wavelength or
wavelengths with one or more fibers. For example, one can
illuminate across the blue spectrum to detect fluorescence. This
embodiment may be most practicable where the source is not
broadband, but is a scanning wavelength source.
[0060] In a variation of this embodiment, an imaging device has a
plurality of probes, each probe comprising an energy source,
optical fiber, lens, etc., as described in the preferred
embodiment. Each fiber has a distal end that is polished at an
angle different from each other such that an energy source
transmitted through each fiber is focused onto a distinct target
site.
Multispectral Embodiment
[0061] By acquiring multiple images at different locations with the
spectrally encoded probe, spectroscopic information within the
bandwidth of the illuminating source may be obtained. Since each
point on the sample is encoded by a different wavelength, moving
the probe while acquiring images allows multiple wavelengths to be
obtained from a single point on the specimen. Accumulation of these
wavelengths reflected from the sample allows construction of a
hyperspectral data set for each point in the image.
Multifiber Array Embodiment
[0062] In yet a further alternative embodiment of the present
invention, shown in FIG. 6, an imaging apparatus 200 is provided
comprising: an elongated hollow generally cylindrical body 202; a
plurality of optical fibers 204 defining an array 206 disposed at
least partially within the body 202 each fiber 204 having a distal
end 208; a plurality of lenses 210, each lens 210 associated with a
distal end 208 of each optical fiber 204 as part of said array 206,
such that each lens 210 is capable of focusing energy transmitted
from an energy source (not shown) through the array 206 on a
distinct position on a target sample 212. Each optical fiber 204 in
the array 206 has a different length such that each distal end 208
and associated lens 210 does not substantially overlap any other
lens in said array 206. This embodiment also incorporates a means,
such as, but not limited to, mechanical, piezoelectric transducer
or the like, for rotating said array about an axis.
Method
[0063] The present invention also provides a method of method for
imaging, comprising: providing an endoscopic probe as described
hereinabove, introducing the probe into a patient; transmitting a
source energy signal to the probe such that the energy signal is
directed at a sample; receiving the reflected energy from the
sample; and, detecting the reflected energy.
Kits
[0064] The present invention provides a kit for performing an
endoscopic procedure, comprising a probe as described hereinabove,
and at least one of the following: a disinfectant, an anesthetic,
and a means for introducing the probe into a patient.
[0065] The present invention also provides a kit for performing a
catheterization procedure, comprising a probe as described
hereinabove, and at least one of the following: a guidewire, an
introducer, a syringe, an expander, and an introducer catheter.
Applications
[0066] In one embodiment, the present invention may be deployed
through a needle with a gauge threshold of 20 or higher. This
embodiment would allow minimally invasive access to most internal
organs for the purpose of primary diagnosis, screening, or biopsy
guidance. For example, areas of the spinal cord can be viewed with
the present invention because the needle gauge threshold of 20
gauge or higher is met by using the endoscope of the present
invention. Previously inaccessible organs such as the ovaries might
be screened using the present invention deployed through a needle.
Liver, pancreas, and brain biopsies could be converted to higher
yield procedures by using the present invention through a needle to
localize the biopsy probe to a region more likely to yield
diagnostic tissue.
[0067] Certain ophthalmological surgical procedures can only be
performed through small holes in the cornea or sclera, allowing
access to the iris, vitreous, retina, and other internal anatomic
structures within the eye. Fetal diagnosis and/or surgery may pose
less of a risk to the fetus when done using the assistance of the
small diameter probe of the present invention. With various
embodiments of the present invention procedures such as mammary
ductoscopy, lacrimal ductoscopy, endoscopic ENT, small joint
visualization, and spinal visualization can be performed.
[0068] The present invention can be used as part of a novel
catheter for use in catheter-based imaging procedures. The
potentially high signal-to-noise ratio of the present invention may
allow imaging of the arterial wall without proximal arterial
occlusion and complete vessel purging. In such an embodiment the
endoscopic probe of the present invention is incorporated in one
catheter lumen to provide imaging of the blood vessel or other
environment into which the catheter is inserted. A second lumen can
deliver therapeutics, such as, but not limited to, thrombolytic
agents, plaque removing agents, antiplatelet agents,
anticoagulants, vasoactive agents, combinations thereof, and the
like. Alternatively, the second lumen can admit a plaque or
thrombus breaking or removal device, such as, but not limited to,
an ultrasonic, laser or cauterizing probe; a set of retractable
teeth forming a claw for grabbing an intravascularly located body;
a flushing or suction device for removing or diluting blood or
other fluid which might obstruct imaging; a means for grasping a
sample of material; or a cauterizing tip or the like may be
employed. Alternatively, other devices, such as but not limited to,
artificial a.v. fistula, other vascular access devices, and the
like may be used. A catheter according to the present invention
becomes possible for intravascular use only because of the small
lumen size needed for the imaging probe as discussed above. Prior
imaging probes were either too large or, if sufficiently small, of
inadequate resolution, to be useful in a single device. With such a
device, procedures previously impossible to perform efficiently now
become possible.
[0069] In an alternative embodiment of the embodiment just
discussed, a catheter can be constructed using a single fiber (or
multiple fibers) in one lumen, whereby the fiber can be used for
photodynamic therapy; i.e., imaging as well as delivering
light-based therapeutic energy during a single procedure. Such
energy may be magnetic, laser, ultraviolet, infrared, fluorescent,
colored or other light energy. In such a device the imaging signal
can be continuous or pulsed, such as alternately with the
therapeutic light energy. One skilled in the art can appreciate the
different permutations of pulsing, alternating, or other sequencing
of imaging and therapeutic signals. Such sequencing can be
controlled externally by a microprocessor or microcomputer which
can be preprogrammed or manually operated by the user.
[0070] In a further alternative embodiment of such a catheter is a
multifiber catheter, where one fiber or fibers transmit imaging
light signal and another fiber or fiber transmits therapeutic light
energy. Such a multifiber catheter may be desirable to have the
image be where there is little absorption across the light
spectrum; in other words, it is preferable to treat where there is
high absorption. As such, it may be desirable to image and treat at
different light wavelengths. In such a catheter where two fibers
are used, the fibers can be arranged to be coaxial or side-by-side.
In such a catheter the point of view of the image may be at a
different point than the point of focus of the treatment light
beam. If the treatment and imaging wavelengths are different, the
angle of the treatment beam incident on the grating will need to be
different that the angle of the imaging beam. In this case, slight
adjustment of the treatment wavelength could allow direction of the
treatment beam on the sample. Another alternative would be to put a
dichroic (wavelength selective) beamsplitter in the distal optics
of the probe that would direct the treatment beam towards the
sample, while allowing the imaging light to pass through unaltered.
In order to bring the angle back to the same point of focus the
angle of incidence of light on the grating can be brought back.
This can be achieved by polishing the end of each fiber at a
different angle so that they both aim at the same target site when
passed through the diffraction grating. In a further alternative a
grism can be used in the distal optics. A grism is a grating placed
in direct contact with a prism. By controlling the angle and the
refractive index of the prism, this optical element allows for
directing light in an arbitrary direction and compensates for the
angular deviation of the diffracted beam from the grating. This is
a very important element of the distal probe since it allows one to
be able to control where one is looking (e.g., straight ahead, side
view).
[0071] It is to be understood that with these embodiments using
light that other electromagnetic energy wavelengths can be used
with the present invention. In certain circumstances even beta,
gamma or other radiation can be used in a targeted manner for
treatment of cancer or other conditions while using a probed as
described hereinabove in the same catheter to image the target
site. Thus, such a catheter as described may be able to reduce a
costly, expertise intensive surgical procedure to an outpatient one
requiring less cost and expertise.
[0072] In a broad aspect of these alternative embodiments, the
present invention contemplates providing one lumen for imaging and
a second lumen for biopsy or irrigation to all mini-endoscopy
applications, not just the cardiovascular system (catheter). For
instance, in mammary ductoscopy, it was found that the second lumen
was necessary for irrigation, insufflation and simultaneous imaging
and biopsy.
[0073] In a further alternative embodiment, imaging can be achieved
through the end of the fiber or through the side of the fiber. This
can be used for a dual-purpose endoscope for imaging and biopsy or
treatment.
[0074] Another alternative embodiment is a combination of an
imaging device as described in the preferred embodiment and a
microsurgical device.
[0075] In another embodiment of the present invention the imaging
probe can be used in situations where a guidewire is typically
deployed. The outside of the bundle of the catheter is a wound
guidewire where the total diameter is less than about 0.3 mm.
Push-pull to create the images as you advance the guidewire. The
probe is the tip of the guidewire to correctly position the
catheter and then to advance another catheter over the
guidewire.
[0076] In another embodiment of the present invention scanned
wavelength can be used, possibly in the telecommunications band.
Scanning the wavelength will allow scanning of the beam at the
distal end at a rapid speed. This would allow simplification of the
detection electronics, since only the intensity of the light will
need to be detected by a single detector as opposed to measuring
the spectrum of light when broad bandwidth light is used.
[0077] One can use the time dependent output of a single detector
to detect light, rather than having to use interferometry or a
linear array.
[0078] Conventional probes are too large to be used in pancreatic
tumor visualization without causing pancreatitis. The small size of
the probe of the present invention allows it to be used in
pancreatic tumor visualization while minimizing the incidence of
pancreatitis.
Industrial Applications
[0079] The submillimeter size of the probe of the present invention
also allows for new industrial applications. One application can be
the textillary weaving of a submillimeter fiber into a fabric.
[0080] An alternative embodiment of the present invention provides
a multiplexed array of a plurality of fibers each fiber having an
associated distal optics. More area can be scanned and the number
of resolvable elements increases with this embodiment. Or, a single
fiber with multiple diffraction elements spaced along the length of
the fiber, e.g., a fiber grating can be used at 1 cm, a second
fiber grating can be used at 2 cm, etc.
[0081] Another application is probe used as an inspection system,
which comprises a cylindrical or other shape (regular or irregular)
body having at least one and preferably a plurality of imaging
fibers extending axially outward from the body in a regular or
irregular array or arrays. Alternatively, the fibers can be flush
or minimally protruding from the body. At one end of the body is an
opening through which either the fibers or fiber passes which is
connected to the detection apparatus. This detector fiber array can
be used in pipes, conduits, or other closed or open systems not
previously accessible to image longitudinally, three-dimensionally,
panoramically, stereoscopically, and the like, using the multiple
fiber array to image multiple points. This would allow for much
more surface area and volume to be imaged and analyzed in a single
procedure than previously possible. An array of this type can
analyze inner wall defects in conduits and the like.
[0082] In a variation on this embodiment, shown in FIG. 7, a probe
has a single optical fiber 300 which has a plurality of grating
lenses 302 (or other lenses) spaced along the surface 304 of the
fiber 300. Each lens 302a, b, c, d, n focuses energy onto a
distinct target site 306a, b, c, d, n.
[0083] Fluid properties can be measured dynamically using the
present invention. Such an application can have a multifiber array
probe within a very small tube. A dye or other detectable substance
can be passed through the tube and the probe illuminate the fluid
and detectable substance to obtain fluid flow dynamics in a given
environment, such as were a weakness in the wall or partial
obstruction has occurred. The present invention can be adapted to
provide a surface built into the probe which can reflect
illuminated light which has passed through an aliquot of fluid,
thus permitting absorption measurements to be taken. Turbidity,
color change, and other conditions may be detected in situ in small
vessels, for example, kidney and gall bladder conditions (e.g.,
stones), seminal fluid composition, and the like. Alternatively, a
cell can be constructed which can continuously admit and pass a
fixed volume of fluid, thus permitting accurate measurement to be
made of the cell volume in situ without requiring surgery,
disruption or occlusion of the vessel. Much more accurate diagnosis
can be made with the present invention rather than external
measurements as must currently be made. With the small size of the
present invention, coupled with the high resolution attainable,
spaces previously impractical to be imaged can now be
visualized.
[0084] The present invention can be developed into a self-contained
remote controlled imaging probe where image data is transmitted by
radio frequency or other signal from within the tube or vessel to
an external receiver.
[0085] The present invention can also be used in veterinary
applications for performing endoscopic procedures on small animals,
fish, birds, reptiles and the like.
Advantages
[0086] The present invention provides for an imaging device capable
of imaging at video rates or higher with up to or exceeding about
one hundred times the number of resolvable points of currently
available fiber optic bundles. The probe of the present invention
is single mode fiber based and can be flexible or rigid, according
to required working parameters. No fill factor problem is
encountered because a single fiber is used. Dead pixels are
eliminated in the present invention. Light transmission efficiency
is maintained because there is no crosstalk compared to multiple
fiber bundles. High efficiency imaging, allowing clear
visualization through turbid fluid may be obtained through
heterodyne detection. Analysis of the group delay and dispersion of
the light returned from the sample allows the acquisition of
three-dimensional information from the object. Hyperspectral data
may be obtained from a series of offset images.
[0087] The present invention can be used to convert many current
surgical procedures into outpatient based procedures. Biopsy
guidance, cancer screening, e.g., abdominal cavity, intracranial,
spinal cord, are possible. The present invention is able to reach
into spaces too small for current endoscopes and maintain a useful
resolution level of obtainable information.
[0088] The probe of the present invention can fit through a 20 or
higher gauge needle. Due to the small size of the probe, it may
also not require anesthesia. Physicians and other medical personnel
may be able perform procedures not previously doable by endoscopy.
Also, lesser trained personnel may now be able to perform
procedures previously performable only by specially trained
physicians and/or surgeons. With the present invention one can
package an endoscope having superior resolution in a diameter
smaller than 1 mm, yet reduce the number of physical components
that make up the endoscope.
[0089] Although only a few exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention as defined in the following claims. All patents,
applications, publications and other documents referred to herein
are incorporated by reference in their entirety.
* * * * *