Note: Descriptions are shown in the official language in which they were submitted.
. W093/ ~ Sl PCT/US92/ ~ 56
, 2ll2s6o
2 LI6HlS-PllMPED HI6H POWER MFOICAL SYSTEM
3 Fi-l~ of.
th~ ~n~e~tio~
s The present invention relates to a system for use in
~edical applications r~guiring light having high power
d aracteristics of laser.3. More specifically, the present
inv-ntion pro~id s a light 50urc~ which i~ c~p~ble of
~ produc~ng ~ b-~ of radiation having ess-nti~lly the s~me
u b-u~ int nsity ~nd spot size as a b~m of radiation
produc-d by a la~r.
: t~ L~ r ~ v .~a nu~b r of optical prop rti~s which ~k~
. ~ th _ ~- p cially-~us~ful. for~ ~ w1d r-ng- -of sci ntific,
indu trial :and:~ dical applications.-~- Th~ two optical
t~ charact ristics ~o~t .co~conly as~ociat-d~with `a be~ of
t~ las-r-radiation..ar- ncoherence~ ~nd- ~onochro~aticityn of
~ ~ :
the ~light b~am.~.- 0th r i~portant characteri~tics-of laser
9 light.are a- high l~vel of be~;int-nsity and th~ ability to
focu -the-light be~ into a very s~al~spot size. -~Although
~' :
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W093~ ~ 51 PCT/US92/~
2 1~2~ 6 o 2
1 the properties of coherQnce and monochromaticity are
2 essential to certain applications, many of the applications
3 for which lasers are used do not require these qualities,
but, rather, only require beam intensity and wavelengths of
s particular interest
~ aser systems are generally expensive to purchase and
operate and, thus, have not been available to many
~ potential users Furthermore, in many of the applications
9 for which lasers are utilized, the expense of the system is
o borne to obtain the optical beam qualities other than the
11 coherence and monochromaticity which are unique to lasers
12 There is a need for an inexpensive optical system capable
of pro~iding an intense bea~ which is capable of being
focused into a sm~ll area
n A prior art lanp-based laser si~ulator is shown in
16 U.S. Patent ~o 4,860,172 i~sued to Schlager et al In the
~7 syste~ disclosed by Schlager, light from an o~nidirectional
conventional light source is collected and focused with
19 conventional n ans into ~n~-optical coupling cone~ which is
~ntend d to-cond ns~ th~ com~entionally focu~ed -beam ~for
launch$ng into a fib-r optic cable
Although the statQd goal~of the '172 patent is to
provide a light source having ~any of the characteristics
of l~ser light, th optical p~r~meters o~ the system
disclosed in the '172-patent are not capable of producing
la~er-s$mulated light-at -an intensity suitable for most
~edical ~pplications There are three parameters which
W093/ ~ Sl PCT/US92/~
2112S60
~ t be optimized to produce light having a high intensity
2 and small spot size using the optical components shown in
3 the '172 patent: 1) the gap spacing between the electrodes,
2) the magnification of the reflector, and 3) the
5 acceptance angle or numerical aperture of the optical
~ fiber. Larger lamp ~ap sizes tend to result in higher
r power output. Large gap sizes, however, also tend to
~ result in larger spot sizes due to the magnification
9 properties of the reflector. The acceptance angle of a
o fiber optic dictates the maximum spot size on the cone at a
given entrance angle which can be completely coupled into
12 the fiber. The acceptance angle is related to the
numerical aperture of the optic fiber by the ~ollowing
t~ equation:
sin (acceptanc~ angle) ~ numeric aperture.
t~ There is a need, therefore, to match the gap size and the
~agni-fication of the reflector to produce a beam which can
t~ be acc pted by the optical fiber for deli~ery to the
t9 tissue. $h system of the '17Z patent ~ttempts to optimize
the coupling of light ~nto the fiber optic through the use
n of a con . More specifically, the '172 pat~nt suggests
z that light can be coupled lnto a fiber optic via a cone
,~ .
which reduces the spot size.
lthough the cone shown in the '1~2 patent will
produce ~ s~ller spot size, the be~m delivered power will
actually be reduced because of the inherent optical
n properties of the coupling cone and the optical fiber. The
, ..~ ...
W093~ ~ 51 PCT/US92/0~ ~
a~ ~?,S 60 4
~ entrance of cone ~as an acceptance angle which determines
2 the first numerical aperture of the cone. Likewise, the
~ cone exit has an output numerical numerical aperture which
actually increases as the output beam spot size is reduced.
m e increased numerical aperture of the cone exit will
cause sig;nificant divergence in the exit beam. The
7 divergence of the beam from the cone exit results in an
~ optical loss because a significant portion of the energy
9 which exits from the cone may not meet the acceptance
o criteria of the numerical aperture of the fiber op.tic. The
net result is a beam which does not have sufficient power
12 to provide the beam intensity needed for many medical
applications.
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W093/ ~ 51 PCT/USg2/ ~ S6
2112560
1 8u~ry o~
2 th- I~-~t~on
The present invention provides a system whieh utilizes
a eonventional light souree to produee a narrowly foeused
5 bea~ of radiation having intensity similar to that produeed
6 by a laser The system is broadly comprised of a
r omnidireetional light source positioned in an optical
~ eavity eomprising a first curved reflector and a second
g reflector whieh can be either flat or eurved The optical
o para~eters of the light souree and the reflectors are
11 matched to produce a narrowly focused beam of intense
12 radiation The seeond mirrored surface has an aperture
therein whieh is plaeed at a point near the seeond foeal
point of the first re~leetor The light souree is plaeed
1S at the ~irst foeal point of the refleetor and the ~eeepting
end of a fiber optie is plaeed at the seeond foeal point of
the refleetor The aperture is positioned sueh that only
rays ~eeting pr~det~r~ined g o~etrieal exit eriteria ean
~ pass through the ap-rture and be aeeept-d by the fiber
2Q optie loeated ~t the saeond foeal point Those rays whieh
do not reet th exit eriteria are refl-eted by the ~irrored
surfaee toward th interior of the eavity Some of the
2S refleeted rays provide additional amplifieation of the
2~ light produeed by the light souree and the path of these
2S rays is altered sueh that they are eventually able to ~eet
Y the exit eriteria and pass through the aperture
n Th- light produeed by the system ean be eoupled into a
W093/OOSSl PCT/US92/054
a ~ 12S 6 o 6 -
1 ~ib~r optic system for delivery to a target area. The
2 dimension of the light source and the focal length of the
3 reflectors in the optical cavity are chosen such thae the
focused beam can be easily accepted by a fiber optic having
s a numerical aperture approximately equal to the inverse of
two ei~eS the ~F/number~ of the re~lector.
.,
.
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.
W093/00551 PCT/USg2~
2112560
1 Bri-f D scription
2 of t1~- Dr~yiD~s
3 A better understanding of the present in~ention can be
obtained when the following detailed description of the
5 preferred embodiment is considered in conjunction with the
6 following drawings, in which:
FIG. 1 is an elevational side view of the optical
system of the present invention showing the light souree
9 positioned in an optical cavity comprising a first curved
reflector and a second reflector.
FIG. la is an elevational side view of the optical
~2 system of the present invention showing a curved second
reflector for redirecting light into the optical cavity.
FIG. 2 is an illustration of the geometry of the
s ~ocu~ d light rays arriving at the sccond focal point of
the reflector.
FIG. 3 is an elevational side view of the optical
sy~t ~ of the present invention showing the electrode gap
- in the light ~ource.
FIG. 4 is a gr~phical illustration of a conventional
continuous wave power level and the pulsed power levels
~ploy d in the system of th~ present invention.
FIG. S is an elevational view in cross section of the
optic~l deliv ry system of the present invention.
FIG. 6 is an illustr~tion of a focussed beam of
radiation d~livered by the syste~ of the present invention.
W093/00551 PCT/US92/054~
2~ 56 ,,.~.,
1 FIG. 7 is ~ graphic~l illustration of the w~velengths
2 o~ ht produced by an arc lamp.
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W093/ ~ S1 PCT/US92/ ~ ~
2112560
1 D-t-~l-d D scr~ptio~ of
2 t~ ~r-~-rr-~ ~ ko~ nt
3 Referring to FIG. 1, the optical system of the presen~
invention is shown in its preferred embodiment. The system
comprises a light source 10 which is mounted in an optical
cavity comprisinq a first curved reflector 12 and a second
r reflector 14 which can be either c~rved or flat. Light
~ produced by the cavity is carried by a fiber optic 20 to a
g delivery system 24, discussed in greater detail below. The
o embodiment of the invention illustrated in FIG. 1 comprises
1l a second reflector 14 which is flat. The alternate
12 embodiment of the optical cavity, shown in FIG. la,
comprises a curved second reflector 14a.
The light source 10 used in the present invention is a
conventional light source in the form of an arc l~mp. The
arc lamp co~prises a cathode 16 and an anode 18 which are
connected to an appropriate power source and mounted in a
u guartz housing 1~. The interior of the housing 19 is
19 fill-d~with ~gas or vapor whic~ produc-s light when
~-exc~t-d by ~n electric current flowing~betw en th~ cathode
21 16 ~nd t~e anode 18. In the arc lamp used iD the preferred
e~bodi~ nt of the present ~invention is a Xenon-Mercury
2~ vapor.
When the lamp is energized, the cathode 16 passes
elec*rons- which are accelerated toward the anode 18. The
26 collision of the el-ctrons with the Xenon or Mercury atoms
2~ caus~s the l-ctrons orbiting those atoms to ~ove to a
~'
W093/ ~ 51 PCT/US92/05456
6 lo
1 higher energy levels or "sti~ulated states ~ When the
2 excited electrons r~turn to their normal energy levels,
3 t~ey emit photons which ha~e a wavelength determined by the
difference betw~en the energy l~vels of the excited state
5 and th~ normal state
FIG l illustrates a plurality of light rays produced
r by the light source l0 The rays 22a-22b and 22a'-22b'
originate at the theoretical center of the first focal
g point of the reflector 12 are all reflected toward the
second focal point of the reflector 12 and can be coupled
into the fiber optic 20 after passing through the aperture
12 i n the second reflector 14 Other rays originate at po1nts
between the cathode 16 and anode 18, as illustrated by rays
u 22c and 22c', respectively These rays are also reflected
by the reflector 12, but fail to pass through the aperture
1~ ~3 in the second reflect~r 14 and, therefore, are reflected
r by the ~irroréd surface of the reflector 14 back tow~rd the
~ int-rior of the cavity, as discussed in gre~ter detail
- b-low ~ So~e r~ys, such as the one illustrated ~y reference
nu~ ral 22d are not refl-ct~d by the f1rst reflector 12 and
thus ~xit the r fl-ctor cavity
The light rays which are focussed at the s-cond focal
point can be accepted by the optical fiber 20, provided
certain constraints are met In general, the l~miting
- factors are the size and acceptance angle of the optical
fib r, the size of the gap of the light source l0 at the
~ f~rst focal point of the reflector 12 and the ~agnification
... .
W093/ ~ Sl PCT/USg2/~56
2112560
11
of the reflector 12
As a general principle, the gap size of the light
3 source is directly correlated with the amount of
el~ctromagn-tic radiation produced with larger gap sizes
5 producing greater power The size of the gap, however,
also has an impact on the ability to converge the light
~ rays for efficient entry into the fiber optic As
~ discussed above, FIG 1 includes an illustration of light
9 rays produced from different portions of the gap between
the cathode 14 and the anode 16 of the arc lamp used in the
preferred embodiment of the invention Since the rays
originate from a band of points, rather than from the
13 theoretical focal point of the reflector, the group of rays
u focused at the second focal point will also arrive in a
b~nd defined by the geometry of the reflector This
16 geometry of the ~rriving rays i8 ~hown in FIG 2, wSich
17 shows a band ~of arri~ing rays passing tSrough the aperture
u h~ving a width of ~D ~ In the c~se where the band width of
the ray~-re~l-cted by the curved r flector 12 and pa~ing
through the ap rture corresponds to the acc~ptance ~ngle of
the ~ib~r optic, there will be effective coupling into the
~iber optic However, in th- c~se where the b~nd width of
the focussed rays exceeds the acceptance ~ngle of the fiber
optic,- there wi'l be ine~ficient coupling of the light into
the fiber optic The bands of incident rays illustrated ~y
ref-rence nu~erals 23 and 23' in FIG 2 do not natch the
nu~erical aperture of the fiber optic and, therefore, would
WO 93/OOSSl PCl`/USg2/OS456
2~.2S6~ ' '
12
1 result in inefficient coupling. In the present invention,
2 these rays are reflected by the mirrored inner surface of
the second reflector 14 and, furthermore, the geometric
parameters of the optical cavity prevent these rays ~rom
5 exiting until the criteria for efficient coupling have been
6 met.
~ If all of the surfaces in the cavity were perfectly
J reflective and had perfect geometry, the returned ray~
9 would be caught in a "reflective loop." However, a number
of factors prevent this phenomenon. The rays which are
returned by the reflector 14 are re-reflected by the first
2 curved reflector 12 will be directed to the interior of the
quartz housing of the arc lamp. Upon passing through the
K gu~rtz, these rays will be refracted slightly. This will
change the direction of the rays as illustrated in FI6. la,
thus preventing them from being caught in a reflective
loop. Horeover, the additional light returned from the
reflective surf~ce will add to the new light being
gen rat-d in the arc gap b-tween which will result in`a
cert~in degree of _~plification of the light produced by
Uh~ ~rc lamp. The ~mount of a~plification is deter~ined by
~he r flectivity of the reflectors and the _bsorption
25 charact~ristics of the various media within the cavity.
2 The reflective loop phenomenon can also be avoided by
controlling the position of the second reflective surface
with respect to the focal point of the first reflector.
Also, a curved second reflector, such as that shown in FIG.
W093/ ~ 51 PCT/US92/ ~ S6
2112S60
13
1 la, ean be used to minimize refleetive loops, thus
2 i~proving the output light generation effieieney.
FIG. la is an illustration of an alternate embodiment
of the presQnt invention utilizing a eurved refleetor 14'
5 having a mirrored inner surfaee. The eurved re~leetor 14'
6 ineludes an aperture 13' passing light rays meeting the
aeeeptanee eriteria of the aeeeptanee angle of the fiber
optie 20. In this embodiment of the system, those ra~s
9 whieh meet the exit criteria, e.g. ray 36, of the cavity
are allowed to pass through the aperture 13'. However,
1l those rays, e.g. ray 38, will be refleeted baek into the
12 interior of the eavity where they will be again re~leeted
1~ by the refleetive surfaee of the elliptieal refleetor 12.
u In the present invention, the are lamp 10 is pulsed to
power l~v l~ several times higher than normally used for
eontinuous wave (CW) operation of the lamp. Thi~ pul~ed
r operation has the effeet ~ of ereating very -intense
produetion of light.- ~-f-rring to FIG. 3, a small sphere
of-pla~a 15 produetion is ~hown ~t the t~p of th- eathode
16 of the are la~p. This~-plas~a is e~used by very inten~e
bo~b~rd-ent of eleetrons _erging from the tip of the
eathode 18. Ihis plasma region normally exists near the
tip of the eathode wh~n the lamp is operatin~ in the CW
mode. In the pres-nt invention, however, the pulsed
operation of the lamp will eause the plasma region to
t~porarily expand to span the entire dist~nee between the
n eleetrodes, ~s illustrated by the pl~sma region 15' shown
W093/ ~ 51 PCT/USg2/05456
56~ l4
1 in FIG. 3.
2 FIG. 4 is a graphical illustration of the power levels
used in the present invention to create the pulsed pl.asma
effects discussed above. The power levels discussed herein
5 are ~or a Mercury-Xenon lamp; however, the principles of
6 pulsed operation can ~e applied to other types of lamps to
t obtain similar results. ~he normal Cw power level shown in
FIG. 4 is approximately 28 amps, lOOO watts of power
9 consumption. Using the pulsed method, however, the current
is increased to more than 50 amps for brief pQriods of
t1 time, e.g., on the order of l to lO milliseconds, resulting
12 in delivered electrical power in excess of 2,500 watts.
lndeed, it is possible to increase the power to even higher
- levels for even shorter periods of time. For example, the
la~p is c~paSl- of sustaining lOO ~ps for p-riods of time
on the order of lOO-SOO ~icroseconds.
-- The pulsed operation of the arc lamp: used in the
~ 1J - pre*ent . invention- produc the intense plas~a region
i~3 ~ b~tw n the two electrod~s, as discussed abov-, thus ~aking
. ~ it po~s~bie to obtain b~am inten~ities at very s~all spot
.siz s ~hich are very si~lar to those produced Sy
conventional lasers.
The various embodiments of the present invention, the
curv d r fIector 12 has an elliptical geometry. Howe~er,
other geo~etries known to those skilled in the art can be
used. For example, a parabolic refl-ctor with an
appropriate lens system could be used to obtain focussing
~.
W093/ ~ 51 PCT/US92/0~ ~
1S 2112560
1 properties similar to that obtained with the elliptical
2 reflector used in the preferred embodiment $he
3 magnification of the elliptical reflector 12 is determined
by the distance between the focal points and the size of
s the ellipse The light source 10 is placed at one of the
6 first focal point of the reflector and an optical fiber 20
r is placed at a second focal point of the reflector
The delivery system of the present invention, shown-in
9 FIG S, is comprised of two lenses configured in a 4-f
o arrangement The delivery system comprises a housing 40
with an optic terminator 42 secured in one end thereof The
2 terminator delivers light from ~he fiber optic 20 to a first
3 diverging lens 44 to produce a collimated light beam The
u colli~ated light beam is p~ssed through an appropriate
s Silt 46, discussed in greater detail below, and is
rec-iv d by a converging lens 48 for focussing the light
radiation on the tissue to be treated m e filter is placed
in the light path to control the wavelengtbs being delivered
9 to th- ablation or coagulation site In ord-r to reduce the
tol-r~nces on the ~ilters, the position of the filter is
chosen in the delivery system between the two l nses ~- m e
filtering operation ~ay be chosen by sliding a filter into a
slot in the delivery system Two grated index G~IN fiber
lenses can replace the normal lenses as presented, as long
as both of them have good transmission in the W and visible
wavelengths A conical tip 50, discussed in gre~ter ~et il
below, assists in the precise delivery of the light to a
W093/ ~ Sl PCT/USg2/05456
~ 16
1 desir-d locat~on on the tissue.
2 The advantage of a 4-f configuration is that the fiber
3 optic output light is focuss~d into a smaller spot at a
given wavelength. ~n the present invention, the advantage
s of using this lens arrangement is that the W wavelengths
are focussed into a small spot closer to the 2Nd lens than
7 the visible wavelengths (due to Chromatic aberrations).
The conical tip 50 is used as a guide to indicate the
9 best focussing point for optimized cutting action. FIG. 6
o is an illustration of the concentric cones of radiation
which result from the light being focused by the 4-f lense
2 system. The W light creates an ablation sight which is
shown touching the surface of the tissue in F~G. 6. The
u visible w~velengths are focussed to just below the ~blation
5 plan o~ th~ delivery system which cause coagulation of the
underlying blood vess~ls be~ore the ablation front reaches
thes~ layers.
?
u - Typic~l spec*ra for Mercury and Xenon la~ps are shown
19 in- FIG ~ ;Th ~rcury lamp has ~everal ~pe~ks in ~V and
~isibl- ~anqes as oppo8ed to the Xenon l~mp which has a ~ore
21 cont~nuous -- sp-ctru~. Mercury-Xenon la~ps have
character~stics very similar to the Mercury with a small
additional Xenon baseline.
~ he Mercury lamp spectrum peaks at 404, 430, 546 and
579 are very close to the peaks of the absorption
characteristic of blood. Tissue, on the oth-r hand, has low
absorption characteristic in the visible, increasing in
.. ~,.
excess of 100 cm~l in the W wavelengths below 320 nm.
Presently, Excimer lasers at 351 and 308 nm have shown very
good cutting action with minimal damage to the sur,rounding
tissue about the ablation
The minimum thermal damage
is partially due to the short pulse widths and photo-
ablation effects of the W Excimer wavelengths.
If only an Excimer
is used for tissue cutting,
will bleed since the blood vessels are not
coagulated to stop the blood flow. Blood coagulation could
be promoted by using a dye laser tuned at the wavelength of
high blood absorption, but with ~uch lower tissue absorption
in which the target of coagulation is the blood and not the
normal tissue. Consequently, an optimized scalpel ~ay be
based on using multiple wavelengths such as W for cutting
~A ~av~l ~n~t~ ar~und ~2n 5~ and 57~ ~he
~ ~_ relative
blood absorption is higher than other wavelengths. The
Mercury lamp (or M rcury X non lamp) has the proper
characteristic to mRtch the needed ~ulti- pectral
ch~racteristics a5 discussed above.
Ths system of the present in~ ntion can be operated in
pulsed ~ode, as discussed above, to produce ablation of a
site using pulse durations on the order of a few
~lliseconds. The short pulse width results in ~inimal
thermal damage to the tissue.
The present invention may be used for cutting tissue if
all available wavelengths are
delivery system. In order to cauterize or coagulate blood,
W093/ ~ 51 PCT/US92/0
th- wav l-ngths in the visible range and of partieular
2 interest the peaks of 546 and S77 nm can be delivered to the
tip with other wavelengths being ~iltered out by inserting
an appropriate filter into t~e delivery system
s Se~eral different wavelengths of lasers from argon (488
and 514 nm) and YAG (1064 nm) and C02 (10,600 nm) have been
used for tissue welding The main goal in tissue we~lding is
to heat the junction of the two sections of tissue (held
9 against eaeh other) to reach temperatures just below their
o eoagulation point resulting in melting of the eollagen of
1l tissue together The melting of the eollagen promotes
12 bett-r and faster tissue healing of the junetion
13 The present invention is eapable of generating a beam
u having wavelength eomponents whieh ean penetrate into tissue
S to depths o~ several millimeters Cons-gu ntly, if the
u syst m ic eonfigured to operate in a eontinuous wave mode,
rather than pulsed mode, the eontinuous low level light ean
s produee suffieient heating of tissue to allow the present
19 inv~ntion to be used for tissue welding as well A
~ t~per~ture monitoring system ean be ineorporated in the
~ deIivery system to provide more aeeurate tissue heat
æ gen-ration thereby avoiding~ over-exposure of the tissue
while allowing more homogeneous welding proeess
In normal surgery, it is usually important to use a
eutting d~viee to penetrate into the tissue or body The
present invention ean be used to ablate tissue and eut
through diSSerent layers of skin The delivery system is
r l
W093/ ~ 51 PCT/US92/054~
2112~;6o
19
1 placed against the ablation site and the ~ight source is
2 activated to produce high power pulses of light. The
3 generated light causes tissue ablation and the operator can
move the delivery system along the desired cutting pattern
5 on the skin. A complete penetration through skin normally
6 requires several passes of tissue removal with a careful
7 inspection of the ablation site.
The present invention also can be used to cauteri~e
9 blood quickly. The cauterizing filter is place in the
o optical path and the syste~ is activated while the delivery
system is pointed toward the bleeding site. This technique
12 can be used to coagulate blood vessels under s~in in depths
u down to 0.6 ~illimeters as well.
u When the operation is completed the cut size is closed
using a few conventional sutures. The system can then be
u configured to op-rate in the welding mode whereby a
continuous low level light is produced. Upon activation,
1~ the delivery system produces mild h ating of the closed cut
19 ar~ as ~t is ~oved along the cut path. The rate of
~ovenent and the heat generated can be calibrated by either
a heat ~nsing feedback syste~ or the experience of the
operator. Nor~al junction `temperatures in the 60-85 C
produces the desired effect.
Although the present invention has been described in
connection with the preferred embodiment, it is not
intended to be limited to the specific form set forth
herein but, on the contrary, it is intended to include such
W093/ ~ S1 PCT/US92/ ~ ~
~,56
~odi~ications, alternatives and equivalents as may -
2 reasonably be includcd with the scope of the. invention as
de~ined by the appended claims.
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