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Description  |
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FIELD OF INVENTION
This invention pertains to the use of lasers in medicine and, more
particularly, to the controllable firing of medical lasers when performing
surgery.
DISCUSSION OF PRIOR ART
Currently, medical and surgical laser output is guided visually by the
operator. The eye, or an optical viewing device, is used to identify the
treatment area and fire the laser. A major problem is that imperfect
visualization of the treatment area leads to poor aim of the laser and
consequently to damage of healthy tissue adjacent to the treatment area.
When the laser device is accurately aimed, it is still difficult for the
operator to know precisely the amount of laser energy to be delivered to
destroy the treatment area without damaging the underlying tissue.
Oversupply of laser energy may lead to an irreversible destruction of
healthy tissue around the treatment site. This destruction can lead to
side effects and complications from the procedure. Undersupply of laser
energy may lead to inadequate destruction of the treatment area and a
therapeutic failure. Furthermore, the problem is complicated because of
the diversity of tissue types that are potential lesions.
U.S. Pat. No. 4,438,765 teaches the use of a laser surgical device wherein
the controlling of the firing of the laser is by a motion detector to
ensure that there is no movement of, say, the eyeball when the laser is
fired for retinal fusion.
U.S. Pat. No. 4,316,467 teaches the use of a laser in removing naturally
pigmented tissue from the skin. The firing of the laser is controlled by
the color of the treatment area sensed by a photodetector. Both of these
patents are basically concerned with the use of a laser in the surgical
treatment of external body surfaces.
In order to enhance the visualization of the treatment area, there have
been developed certain dyes which can selectively stain the diseased
tissue. The difference in the optical property of the stained tissue and
the unstained healthy tissue improves the visualization of the treatment
area. U.S. Pat. No. 4,336,809 is typical of the teaching of a
photoradiation method for tumor enhancement with hematoporphyrin dye,
wherein the dyed lesion site is bathed with radiation of a particular
wavelength to cause it to fluoresce.
When dealing with lesion sites within the body cavity, it is necessary to
deliver the laser energy internally to the lesion site. U.S. Pat. Nos.
3,858,577 and 4,273,109 are typical of fiberoptic light delivery systems.
In spite of all of this existing technology, there is still not available a
laser surgical system which is capable of performing laser surgery within
the body cavity such that the laser effects are automatically monitored to
control the output of the laser and to terminate its operation before
there is a destruction of healthy tissue around the treatment site.
BRIEF SUMMARY OF THE INVENTION
It is, accordingly, a general object of the invention to provide an
improved method of delivering laser energy for the treatment of an area
within a body cavity.
It is a more specific object of the invention to provide such laser energy
only as long as the treatment area shows the need for such laser energy
and to terminate the application of the laser energy when the malignant
portion of the treatment has been destroyed.
Accordingly, with this aspect of the invention, there is provided a method
for radiating a treatment area within a body cavity by introducing an
elongated flexible radiation transfer conduit into the body cavity until
the distal end thereof is operatively opposite the treatment area.
There is a particular optical characteristic of the treatment area which is
photoelectrically sensed and as long as this optical characteristic is
sensed, laser pulses are periodically transmitted into the proximal end of
the conduit for transfer to the distal end and the treatment site.
In accordance with a feature of the invention, if the treatment area has no
inherent optical properties which are sufficiently different from the
surrounding healthy tissue, then before the treatment begins there is
introduced into the treatment area a reagent which will cause the
treatment area to be characteristically stained so that when the
photoelectric sensing takes place the optical properties of the
characteristic staining will be sensed.
According to a specific feature of the invention, there is contemplated a
method of destroying atheromatous plaque within an a rtery of a patient
comprising the steps of initially administering to the patient a non-toxic
atheroma-enhancing reagent which causes plaque to have a characteristic
optical property when illuminated with a given radiation. Thereafter, a
catheter system including fiberoptical cable means is introduced into the
artery such that the distal end thereof is operatively opposite the plaque
site. There is then introduced into the proximal end of the fiberoptical
cable the given radiation. When plaque is illuminated with the given
radiation, a characteristic optical property is sensed at the proximal
end. There is then fed via the cable means from the proximal end to the
distal end periodically occurring laser pulses until the characteristic
optical property is no longer sensed.
In order to implement the method of the invention, there is contemplated a
laser system having fiberoptical bundle with a central optical diagnostic
means, a receiving fiberoptical array means annularly disposed about the
diagnostic means and a treatment fiber optical array means annularly
disposed about the receiving fiberoptical array means. A treatment laser
source is connected to one end of the treatment fiberoptical array means,
a diagnostic light source is connected to a corresponding end of the
central fiberoptical diagnostic means and a radiation detector is
connected to the corresponding end of the receiving optical fiber means.
Another implementation of the method of the invention contemplates the use
of a single optical fiber which transmits time multiplexed radiation. A
further implementation contemplates two fibers, one handling diagnostic
radiation and the other multiplexed treatment and sensed radiation.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, the features and advantages of the invention will be
apparent from the following detailed description when read with the
accompanying drawing in which:
FIG. 1 is a block diagram of a laser system utilizing the invention;
FIG. 2 is a schematic longitudinal section of the fiber optic cable of the
system of FIG. 1;
FIG. 3 is a cross-sectional view of said cable along the lines III--III of
FIG. 2;
FIG. 4 is a block diagram of a portion of the laser system of FIG. 1
utilizing a single optical fiber; and
FIG. 5 is a block diagram of a portion of the laser system of FIG. 1
utilizing two optical fibers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The invention will be described utilizing the example of the destruction of
an atheromatous plaque 4 from the artery 6 of FIG. 1. Initially, the
patient is administered a dose of a dye to enhance the contrast between
the treatment site (plaque) and the healthy surrounding tissue. A typical
dye is tetracycline which has the property of fluorescing when radiated
with an ultraviolet light. This dye has a special property of accumulating
within the plaque relative to normal healthy tissue. Therefore, a
predetermined time after the administration of the dye, the fiberoptic
cable 8 is inserted into the artery with the distal end thereof opposite
the treatment site. The optical cable 8 in a first embodiment (see also
FIGS. 2 and 3) includes a central optical fiber 8a coupled to the output
of light coupler 26, an annular array of optical fibers 8b surrounding the
central fiber 8a connected to the input of light coupler 28, and an outer
annular array of cables of fibers 8c is coupled to the output of light
coupler 16. Light coupler 26, of conventional design, receives light from
the diagnostic light source 22 via the optical modulator 24. Diagnostic
light source 22 for the present example would be a source of ultraviolet
light. If other dyes were used, then appropriate light sources for those
dyes would be selected. The light indicated by the single arrowhead line
feeds the input of modulator 24 whose output is fed to the input of
coupler 26. The modulator 24 can be of a conventional opto-accoustic
modulator or an electromechanical shutter which passes or blocks the light
in response to an electrical signal from controller 32 (note all
electrical signal lines show double arrowheads). Thus, the presence or
absence of a signal on line 32a from the controller 32 can close or open
the light path between diagnostic light source 22 and light coupler 26.
The proximal end of array 8b feeds light into the light coupler 28 whose
output is fed into the wavelength selector 34 which selects light
corresponding to the predetermined characteristic wavelength to be
detected. In turn, the selected light feeds detector-amplifier 30 whose
output is fed via signal lead 32b to the controller 32. The
detector-amplifier 30 can be the combination of, for example, a photodiode
which drives a transistor amplifier, a photomultiplier, or in and of
itself can be a phototransistor. Thus, whenever light is received from
array 8b a signal will be transmitted to controller 32. The
detector/amplifier 30 is controlled by signals on line 32e from controller
32.
Treatment laser 10 will transmit light to modulator 12 which is controlled
by signals on line 32c from controller 32. The controlled light from
modulator 12 is fed to a conventional beam spliter 14 with a portion of
the light being deflected to detector/amplifier 20 and the remaining light
passing to the input of light coupler 16. The output of light coupler 16
is fed to the proximal end of optical fiber array 8c. Beam splitter 14
also feds part of the beam to detector/amplifier 20 which in turn feeds a
signal on line 32d to controller 32 which provides feedback sensing of the
laser output to ensure constancy of the amplitude of the laser output over
time.
In operation, after the dye has been inserted and the cable 8 is in place,
the diagnostic light source 22 passes light via modulator 24, coupler 26
and array 8a to the treatment site 4. The plaque in the treatment site
will fluoresce and the fluorescence will be picked up by the array 8b and
fed to the light coupler 28 and, thence, to the wavelength selector 34.
The output from the wavelength selector 34, corresponding to the
characteristic fluorescent emission of tetracycline, is fed to the
detector/amplifier 30 which in response will emit a signal on line 32b to
controller 32. The controller 32 in response thereto will send a signal on
line 32c to open the modulator 12 to emit laser energy of a predetermined
power and wavelength for a set time interval. Accordingly, a pulse of
light from treatment laser 10 will be fed via the beam splitter, light
coupler 16 and the array 8c to the treatment area 4. Because light
reflected from the treatment area can be very great during the time of the
laser pulse, controller 32 via line 32e feeds a signal to
detector/amplifier 30 to turn off the detector for a prefetermined time
interval. This signal can also be fed to modulator 24 to prevent the
radiation of ultraviolet light during the laser pulse. Controller 32 then
switches signals on lines 32c and 32e at the prefetermined timing delays
such that the laser output is blocked and the fluorescent light can again
be sensed from the treatment site. If the fluorescence is then detected
indicating that plaque is still present, the detector 30 will send a
signal to controller 32 which, again, switches the signals on the lines
32e and 32c, initiating another laser pulse. This sequence continues until
no fluorescence is detected indicating that all plaque has been destroyed.
At that time, no signal is fed to controller 32 and no further laser pulse
is generated. In this way, using the probe-and-fire technique of the
invention, the possibliy of destroying healthy tissue is minimized. The
controller 32 in its simplest form can dispense with the use of
detector-amplifier 20 and can merely be a monostable device which is
momentarily triggered on a pulse from line 32b and then reverts to its
rest state. The paraphase output of this device can be connected via
appropriate amplifiers to lines 32a, 32b and 32e.
To facilitate the positioning of the laser catheter within narrow tortuous
pathways a single flexible optical fiber 8' (or small diameter bundle) is
used (See FIG. 4) instead of the multibundle cable 8 of FIG. 1. More
particularly, the light couplers 26, 28 and 16 connected to their
associated bundles 8a, 8b and 8c are replaced by a single
multiple-wavelength coupler MWFC which optically couples
multiple-wavelength beam splitter MWBS to single optical fiber 8'.
Multiple-wavelength beam splitter MWBS receives laser light from beam
splitter 14 (FIG. 1) along a given incident angle path and diagnostic
light from modulator 24 (FIG. 1) along another given incident angle path
and transmits such received light via a port along a common
transmit-receive path to multiple-wavelength light coupler MWLC.
Furthermore, radiation from the treatment site 4 is fed from
multiple-wavelength coupler MWLC via the comnon transmit-receive path into
the port of multiple-wavelength beam splitter MWBS. This light is emitted
therefrom to wavelength fitter 34 via a further path having an angle
different from the two given incident path angles. Because of the nature
of the multiple-wavelength beam splitter MWBS it may be possible to delete
fitter 34 and feed detector/amplifier 30 directly from the beam splitter.
The so-modified system operates in the same manner as the system of FIG. 1.
In FIG. 5 the fiber optical configuration is modified to a dual fiber
configuration. This configuration may put less demands on the
multiple-wavelength beam splitter MWBS and may permit more diagnostic
light to reach the treatment site 4. In this embodiment a single fiber or
bundle 8a' is connected to light coupler 26 (FIG. 1). The fiber 8" or
narro diameter cable is connected to multiple-waveength light coupler MWFC
which is optically-coupled via a comnon transmit-receive path to the ports
of the multiple-wavelength beam splitter MWBS. Laser light is received
along a given incident angle path from beam splitter 14 (FIG. 1) and
fluorescent light from coupler MWFC is fed from multiple-wavelength beam
splitter MWBS via an output optical path having a different angle to
wavelength selector 34 (FIG. 1). As with the embodiment of FIG. 4 fitter
34 may be omitted.
Operation of the system utilizing the embodiment of FIG. 5 is the same as
the other embodiments.
While only a limited number of embodiments of the invention has been shown
and described in detail, there will now be obvious to those skilled in the
art many modifications and variations satisfying many or all of the
objects and features of the invention without departing from the spirit
thereof. For example, while only the treatment of plaque has been
described the invention can be used as a treatment of other diseases such
as tumors(cancer), stones in urinary tract and gall bladder as well as
prostate obstructions. In addition, depending on the nature of the
treatment site, the appropriate dye is selected to enhance the contrast
between normal tissue and malignant tissue. When the treatment site is a
tumor, one can successfully use hematoporphyrin or its derivatives. In
some cases, inherent differences in optical properties between the
treatment site and the surrounding healthy tissue may eliminate the need
for a dye. Again, depending on the treatment site and the dyes involved,
the diagnostic light can be ultraviolet, infrared, white light, etc.
Furthermore, again depending on the treatment site, the laser source can
take many forms such as argon, Nd-yag, carbon dioxide, tunable dye, and
excimer lasers with pulse or continuous output. The choice of the
diagnostic light source is predicated on the optical characteristics of
the dye and/or the treatment site. However, the choice of the coherent
light source for the treatment laser does not have to match the absorption
peak of the dye. The treatment laser can be any wavelength that destroys
the diseased treatment site. Normally, there is a risk that this light
will also destroy healthy tissue. However, the possibility does not exist
since once the diseased treatment site is removed, the means for
triggering the laser pulse is also removed.
The fiberoptic cable can be coupled with catheter designs which include,
but are not limited to, such features as endoscopy, balloon devices,
steerable guiding systems, multiple lumens for infusion and suctioning,
ultrasonic guidance, monitoring or ablation, pressure and temperature
monitoring and catheter centering devices.
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