CA1269718A - Laser catheter with energy feedback system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A control system for a laser catheter device wherein the control system is provided with a device for determining the intensity of laser beam energy at two points, one of which is at the distal tip end thereof, and with he other being interposed along a transmitting column remote from both the source of laser beam energy and the distal tip. A beam splitter (dichroic filter) is provided for diverting a first portion of the laser beam energy onto a first detector. Energy passing through the beam splitter is ultimately directed onto a fluorescent member or device disposed adjacent the distal tip, with the fluorescent member of device being capable of emitting or generating radiant energy at a wavelength significantly different from that of the incident laser beam energy. The radiant energy generated by the fluorescent device is directed onto a second surface of the beam splitter, and ultimately onto a second detector. First and second signal processing device responsive to the first and second detector are utilized to control a shutter, such as a dual shutter, which is arranged to interrupt the passage of laser beam energy through the catheter system upon the occurrence of anomalous levels of laser beam energy at either the first or second detector.

Description

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The p~esent invention relates generally to an improved control system for a laser enhanced transluminal catheter device, and more particularly to a such control system utilizing an optical feedback system capable of monitoring the output intensity or energy of the laser beam at the distal tip of the catheter. The feedback signal is normalized relative to that level detected at a point disposed relatively close to the laser generator component per se.

The control system of the present inven-tion is par-ticularly adapted to a laser enhanced transluminal angioplasty catheter whereln obstructions in blood vessels may be treated with exposure to laser energy to obtain either a partial reduction and/or elimination of the obstruction by means of such exposure. An optical fiber is utilized for transmitting the laser beam energy from the generator onto the obstruction located in the zone to be treated. The optical fiber can also be utilized for the purpose of providing illumination asld optical vi~wing. Laser enhanced transluminal angioplasty catheter devices are considered valuable tools for the treatment of commonly encountered forms of arteriosclerosis and the like.

Atheroclerosis is among the more commonly encountered forms of arteriosclerosis as it relates to the human heart and circulatory systemr which typically has been treated by drugs, angioplasty catheterization, and also through open heart bypass sur~ical procedures. Of these various forms of treatment, angioplas-ty cathe-terizatiorl has been ~ound to be a treatment of choice ln certain situations. Such treatment normally involves initially bringin~ a balloon-tipped catheter proximate the material forming the obstruction matter in vessel, with the 3~ distal tip catheter normally being forced through the obstruction asld the balloon portion is thereafter lnflicted so as to cause dilation of the obstruction.

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This procedure is effec-tive in reopening the blood vessel and restoring substantially normal circulation in many cases. This procedure is, however, especially dependent upon the skill o~ the cardiologist, and particularly as that skill pertains to manlpu-lation and ultimate direction and control of the catheter. Nor-mally, some assistance is provided through fluoroscopy tech-niques, typically through the incorporation of radiopaque members along the catheter. I-t is further recognized that angioplasty catherterization is frequently a procedure limlted to those patients having obstructions which have not totally occluded the blood vessels to the polnt where the nominal diameter of the dis-tal tip of the catheter would otherwlse prevent passage of the catheter through the obstruction prior to dilation of the vessel.

secause of its application to surgical procedures, laser enhanced transluminal angioplasty catheters have been developed. In such devices, the catheter is provided with a source of laser energy, and this laser energy is directed to the site along optical fibers.
By way of background, dilating catheters are known, having been disclosed in U.S. Patent Nos. 4,040,413; 4,271,839;
and 4,299,226. Catheter devices including optical fibers are disclosed in U.S. Patent No.s 3,123,066; 3,136,310; 3,858,577;
~,146,019; and ~,273,019. Also, laser enhanced catheters are disclosed in U.S. Patent Nos. 3,467,098; 3,538,919; 3,843,865;
and 4,266,548.

An example of multi-technology catheters is descrlbed in U.S. Patent No. ~,207,874 and/or the American~Journal o Caldiolo~y~ 50:8QJ 81 (December 1982). In U. S. Patent 1"2()7,871~7 and of which the ~L3~ artlcle is an elaboration, ~
~iber optic directable ca~heter is disclvsed, with the device including a bundJe of laser transmitting fibers and a centraJly disposed lumen for perrnitting the suction relnov;li of vaporized waste rnaterial after 5 exposure to laser bearn energy. Upon completion of the tunneling procedure, blood samples which are collec~ed in a transparent e%ternal collection reservoir visually indicate the extent of completion of the procedure to the operator.
In laser enhanced transluminal angioplasty cathetcr devicesl it i5 10 desirable for the operator to determine and to be reasonably confident that the laser energy being directed to the site is within certain predetermined desirable limits, that is, the energy is known to exceed a certain base or rninimum threshokl level, while not exceedin~ a certain upper limit. An indication that tlle laser beam energy is within 15 predeterrnined limits will enable the procedure to be more reliable, expedient, reproducible, and ef-Eicacious. Inasrn~lch as optical fibers are being employed, alon~ with other electro-mechanical and op-tical systems, proper evaluation of the operating parameters is desired. For example, the rupture, fracture, or occurrence of damagc to the optical fiber rnay 20 reduce the energy level available at the distal tip of the catheter to such an extent that tlle procedure would be generally ineffectlve. On the other hand, excessive quanti~ies of laser bealn energy available at the distal ~ip oE the catheter may adversely affect the quality of the procedure.
The present invention utilizes a control system which is 25 interposed along the optical fiber segments which are provided to transrnit laser energy frorn the generator to the distal tip. The control system includes an electromechanical shutter and a beam splitter disposed along the beam path. ~n attenuator and a focusing lens are located orthogonal to the energy beam, and a predeterrnined proportion of the 30 ~ ~26~7~

energy is reilected ancl/or sarnplecl by the bearn splitter and directecl into tlle attenu.~tor .Ind focusing Icns arld on~o d first detector. rhe detccror is, in turn, coupled to a power Icvel mor)itor. On the catheter side of the bearn spJitter, and also ortho~onal to the be~m, is an Interference Iilter and a second focusing lens. A~ the distal tip of the optical fiber there Is 5 disposed a fluorescer)t element. The terrn "fluorescent" is intended to be used in a comprehensive sense, such as the response generated in such an element when irradiated witl) electrornagnetic radiation of a given wavelcn~th, with the response being the emission of radiatk~n ~t a second and longer w;lvelength. One particularly desirable optically re~ctive 10 device is a sapphire doped to Eluoresce when transmitting laser energy.
Since the fluorescent energy which is E enerated by the incidel)t Jaser ener~y is at a wavelen~th si~nificantly different frorn that of the laser energy, the fluorescent energy is transrnitted or reflected back through the optical fiber and onto the catheter facing surface of the beam 15 splitter. The fluorescent ener~y is then reflected by the catheter facing surface of the bearn splitter (dichroic filter) into a focusing lens and thence onto a second detector. The output of the second detector is typically amplified and fed into a threshold detector. The output of the threshold detector is, in turn, coupled to the shutter systern as well as to 20 the power supply of the laser generator.
In tlle event the distal portion and/or distal tip of tile optical fiber becomes dalnaged, the quantity or output of fluorescent ener~y generated by the optically reactive means will becorne diminished and the threshold dctector will respond to the drop with a reductlon in signal 25 amplitu(le. This change, as detected, will create a si~nal which may be ~ed through a feedback loop which will, in turn, either shut off the laser ~enerator and/or close the shutter system. The system of the present invention permits simultane~ous monitoring of the output of the 1;15er generator and the output of the optical fiber. In certain applications, an 30 .

~26~7~1 attenuator may be placed in the laser beam path in front of the shutter system. The ratio of the optical fiber output relatlve to the laser generator output is monitored continuously, and in the event the ratio falls outslde of a predet~rmlned range because of a failure of a system component, the entire system may be automatically shut down.

According to the present invention there is provided in a laser enhanced transluminal angioplasty catheter system includ-lo ing a catheter having a proximal end and a distal end, a sourceof laser beam energy, lens means for focusing the laser beam energy from the source onto an optical fiber for providing a beam transmitting fiber column for transmission of laser beam energy from the proximal end of the distal tip end of the catheter, a control means interposed along said optical fiber at the proximal end of said catheter, said laser enhanced transluminal anglo-plasty catheter system being characterized in that ta) generator means are provided for generating a laser beam, an optical fiber column extendiny along the length of said catheter system for transmitting said laser beam to the distal tip of said catheter and for controllably discharging said laser beam from said catheter distal tip, a laser beam energy evaluation zone at the proximal end of said catheter system between said generator means and said distal tip, and means for accessing at least a portion of said laser beam within said beam energy evaluation zone during operation of said laser generator and sai.d catheter system; (b) said beam transmitting fiber column including means for deliver-ing las~r beam energy from said column to said laser beam evalua-tion zone; ~c) shutter means within said beam energy evaluation zone having means for controllably interr.upting the passage of laser beam energy through said beam energy evaluation zone and along said beam transmitting ~iber column upon detection of an anomalous signal; ~d) beam splitter means disposed within said beam energy evaluation zone for diverting a portion of said laser beam energy passing through said beam energy evaluation zone for directing said diverted portion onto a first detector means, and ~2~

means for simultaneously enabling the passage o~ khe non-diverted portion of said laser beam energy through said beam splitt0r means and along said beam transmitting flber column to said dis~
tal tip; (e) optically reactive means disposed at the distal tip of said catheter along the path of the non-diverted portion of said laser beam energy and axially distally of said optical fiber column for normally receiving and normally transmitting substan-tially all of said non-diverted laser beam energy therethrough, and having optically reactive responsive means incorporated lo therein for generating radiant energy at a wavelength signifi cantly different from khat of said laser beam energy while being stimulated with said laser beam energy transmitted along said beam transmitting fiber column and received by said optically reactive means; (f) means for simultaneously transmitting said stimulated radiant energy from said optically reactive means as an energy sourc~ through said optical fiber column and thence onto said beam splitter means for diversion of said stimulated radiant energy onto a second detector means during the operation of said laser beam generator and wlth sald beam transmitting fiber column simultaneously transmittlng laser beam energy from said generator means to said optically reactive means; (g~ first and second signal processing means responslve to said flrst and second detector means respectively; and (h) shutter control means responslve to the output of said first and second signal process-lng means for closing said shutter means and lnterrupting thepassage of laser beam energy from said generator means through said beam enaryy evaluation zone upon detection of an anomalous signal from one of sald first and second detector means. Suit-ably the catheter system is particularly characterized in that said beam splitter means is a dichronic ~ilter arranged for rnaxi-mum transmission of incident lasar beam energy. Desirably the catheter system is particularly characterized in that said opti-cally reactive means is a fluorescent lens element which emits fluroescent energy upon stimulation by laser beam energy. More desirably the catheter system is partlcularly characterized in that said fluorescent lens element contains a dopant and is .
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arranged to fluoresce and emit 1uorescent energy at a waveleng-th yreater than that of the incident laser beam energy. Suitably the catheter system is particularly characterized in that said optical flber colurnn is arranged in first and second spaced apart flber optical segments, and a beam energy evaluation zone ls interposed between said first and second spaced apart fiber opti-cal se~nents.

Thus, in accordance with the present invention, a sys-tem is provided for feedbacks of information from the dlstal tipof the catheter without the need for additional optical fibers or wires to be employed in the catheter. Furthermore, the fiber optic tip at the end of the catheter is properly protected. The sys-tem of the present invention further allows simultaneous mea-suring and/or comparing of the laser generator output and thecatheter output, with the response time of the feedback system being extremely fast for proper system monitoring. In the event of a mal~unction, or if the output deviates form a pre-estab-lished or predetermined range, the system may be immediately shut down.
In addition to the control functlon, the placement of a fluroescing lens at the distal tip of the optical fiber provides a convenient means for focusing andJor diverging the laser beam energy. This lens also provides protection for the tip of the optical fiber. Such a lens also makes it possible to monitor the temperature level existing at the distal tip of the optical fiber. Temperature monitoring is an available feature which may be accomplished by intermittent pulsing of the laser along with a measurement of the response tlme of the incident fluorescent energy. The output of the catheter may be monitored relakive to the laser output so as to assure operation at the appropriate and desired level.

35ThereEore, the present invention provides an improved feedback control system for laser enhanced transluminal angio-- 6a -~l , plasty catheter devices, wherein the control system provides a means for moni-toring the energy level available from the. laser generator, as well as that available at the distal tip of the laser enhanced catheter through feedback from the distal tip.

The present invention also provides an lmproved laser enhanced transluminal angioplasty catheter devlce which provides a means for monitoring the laser output at the distal tip of the catheter relative to the output of the laser generator, and with the control system employing a feedback arrangement from the dis-tal tip of the catheter without requiring the presence of any additional optical fibers or wires in the catheter to accomplish the monitor function.

The present invention again provides a control system for a laser enhanced transluminal angioplasty catheter device which employs a feedback system havlng a rapid response which is adapted for monitoring the output at the distal tip of the catheter, and which will shut the system down in the event the output deviates from pre-established ranges.

The present invention will be further illustrated by way of the accompanying drawings, in which:-Figure 1 is a schematic diagram illustrating one embod-iment of the present invention, and illustrating the manner in which the contro:L system simultaneously monitors or measures the output energy from the laser generator, as well as the energy received through the transmission system and accordingly avail-able at the distal tlp of the catheter;

Figure 2 is a schematic diagram illustrating the details of the optical unlt utilized in the laser enhanced trans-luminal angloplasty catheter feedback system with the energy feedback belng available from the distal tip of the catheter; and - 6b -, ~Z6~7~

~ lgure 3 is a fragmentary detail schematic diagram of the distal tip portion only of the catheter assembly.

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In accordance with the preferred modiflcatlon o~ the present invention, and wl-th partlcular attentlon being directed to Figure 1 of th~ drawlngs, the laser enhanced transluminal angioplasty catheter system generally designated 10 includes a transluminal angioplasty catheter member II having a proximal end 12 and a distal tip end 13, and with the catheter incorporating optical fibers for transmission of laser beam energy therethrough. Laser energy is provlded from laser head 14, driven by power supply and control 15. Laser heads for the genera-tion of laser energy for laser ~nhanced transluminal angioplasty catheter devices are commerclally available, as are u power supply and control systems therefore. The ~nergy generated at the laser head 14 is transmitted through the wall of the head, along column 16, and into focusing lens 17. Focusing lens 17 directs the energy along the column shown as at 18, and into a first optical fiber segment as at 20. Optical fiber 20 is of a 1~ convenient length, such as a length of, for example, 10 meters.
The terminal end 21 of optical fiber segment 20 is designed to pass laser energy along an energy cone as at 22, and into focusing lens 2~. The beam passing through lens 24 is preferably arranged in a collimated form or parallel path as at 25, and 2U passed into electromechanical dual shutter 26. In normalO dual shutter 26 permits the beam to pass therethroughr as is indicated in Figure 1, and in the event of an malfunction as will be described hereinafter, electromechanical dual shutter 26 will close its panel members or vanes 27 and 2~ so as to interrupt the passage of laser beam energy therethrouyh. The laser energy exiting shutter 26 is shown in beam form 30, and passes onto beam splitter 31. Beam splitter 31 may conveniently be and is preferably a dichrolc filter arranged for substantial or maximum transmission of lncident laser beam enPrgy. The small portlon or 3U sample of incident laser energy which ls reflected o~f the surface o~ beam splitter 31 is indicated as at 32, with the balance of the energy passing 3~

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througll spli~ter 31 and alon~ beam column shown at 33. 13eam column 33 passes throu~ll focusln~ Icns 34, and Into a second se~rrlcnt o2 optlcal fibers 35 contalned witl-in a lurnen f~rrned In laser enhanced translumln~l an~ioplasty catheter 11. ~ the distal tlp of th& catheter 11 Is a fluorescent element or means for generatlng radiant ener~y at a 5 wavelength slgnificantly different from that of the incident laser beam energy. Typically, the fluorescent rneans may be a sapphire element containing a dopant which generates fluorescent energy or other radiant energy which is emitted at a wavelength slgnificantly different from that of the incident laser beam energy. The sapphire element, such as 10 optically reac~lve or doped sapphire element 37 is, of course, commercially available. One such useful dopant Is chromlum. Whlle a sapphire element containing a dopant has been found to be desirable for use as the material of construction for element 37, it will, of coursei be appreciated that other fluorescent substances may be ernployed as well. 15 It is desirable that the material be highly transmissive to ener~y within the wavelength of the laser beam, and further tl)at It have the property of generating fluorescent enerKy or other detectable radiant energy at a wavelength significantly different from that of the incident laser beam energy. 2 0 The radiant energy generated by the Iluorescent sapphire element 37 is recelvcd by and passed along optlcal flber 35, In the directlon Indicated by arrows 39-39, and onto the catheter faclng surface of beam splitter 31. The beam splltter (dlchroic fllter) which In thl~ case, reflects the energy of the wavelen~th generated by the fluorescent 25 member, passes along the path Indlcated by arrows 40-40 and ultimately received at the active surface of cletector 41. This portlon oI the apparatus wlll be described in detall hereinbelow.
Turning now to the means Ior moni torln~ incldent laser light from ~he laser genetator or head 14, this sample of the overall output 30 3~2~

energy o~ the laser passcs along beam column 32 throu~h attenuator 43, focusing lens 44, and onto ~he activc surface of radiant energy dctcctor 45. A power level indicator as at 46 is In circult wlth detector 45, thus providing an indication of the power level of Incldent l~ser energy received at the incoming surface of beam splltter 31. Furtherrnore, the 5 output of detector 4S Is coupled along llne 48 to power supply and power contr~ through the control loglc. Detectors such as detector 4S, power level indicator 46, and the correspondlng Input to power supply and control 15 are commercially available.
Turning now to the reflected light which is 8enerated by 10 optically reactive member 37, received upon and transmitted Irom ~he second surface of beclm splitter 31, such as is shown at 40-40, an interference ~ilter Is sllown in the path as at 50, with this $11ter bein~
adapted for maximum transmission of incldent radiation at about 6940 Angstroms. This filter will typically have Its peak ~ransmlsslon at the 15 range of maximum generation of the optically reactive member 37. The signal generated by detector 41 i5 passed through a typical pre-ampll~ler as at ~2, for transmission to threshold detector S3. The output o~
threshold detector 53 is norrnalized with respect to the output laser energy detector and is transmitted to separate logic controls, one belng 20 an input to electr~mechanical dual shutter 26, the other being an Input, as at 54, to power supply and control 15. As has been previously indicated, if the normalized output of thresllold detector 53 Is outside of prescribed and desired limits, the active vanes 27 and 28 of shutter 26 are closed so as to totally interrupt and shut clown the transmission of laser beam 2 5 energy into the catheter 11.
It will he appreciatecl, therefore, that the laser beam energy passing between focusing lens 24 and focuslng lens 34 is, in effect, passing through an evaluation zone for controlling the amount of energy avallable in the overall system, and also available at the distal tip of the laser 30 enhanced transluminal angioplasty ca~heter 11.

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Attention is now directed to ~igure 2 of the drawin~s wherein the optical unlt for the laser catheter is shown In Kreater detall. Slmllar numerals are utilized to identify similar itelns from that shown In Flgur~ I
where practical.
In tl e system of Figure 2, and witl~in tlle laser unlt block is laser 5 head 15A driven by power supply 15B so as to generate a column of laser beam energy as at 16. Focusing lens 17 provides a means for focusing and directing the bearn into the first optlcal flber segment as at 20, with se~ment 20 being typically 10 meters in lengttl.
The control unit block commences ~enerally at the termlnal end 10 of the first optical fiber segment, as also shown In Fi~ure 1. I ens 18 Is employed to colllmat~ the beam and pass the b~am through an attenuator 60. Attenuator 60 is utllized to control the amount of the transmitted power through tlle system. Light passing through attenuator 60, as previously indicated, passes through electrornechanical dual shutter 26 15 and onto the first surface of beam splitter 31. In this embodirnent, beam splitter 31 is a dlchroic filter, with such dlcl rolc fllters belng, of course, commercially available. Dichroic filter 31 is selected so as to provide for maxlmum transmission of laser light, with only a small percenta~e being reflected along path 32, as prevlously set forth In the embodlment of 20 Figure 1. Attenuator 43 is ernployed to control the arnount of energy incident to and recelved upon detector 45. The output from detector 45, as indicated previously, is convenlently displayed on power level Indlcator 46, and ultimately reccived at thc flrst control Input ISC to power supply ISB. ~ 25 The laser enllanced transluminal angloplasty catheter 11 as illustrated In Flgure 2 Is provide l with one or more additional lumens for the transmission of fluids, with the lead-in to the ~luid transmitting lumen being shown at 61. A protective shield or tubing for ca~heter 11 Is Illustrated at 62, with the tubing for tl)e laser enhanced transluminal 30 ~L ~26~7~ b angioplasty catheter deYice 11 beln~ preferably lormed of an FDA
approved material or substance such as, for example, polyethylene or equivalent. A me~alJic or glass sleeve is provided at 63 for receivlng optical fibers and the sapphire element. In thc appJication of a ~lass tube, additional radiopa(lue bands~ such as at 64 and 6S, are employed in order 5 to assist in determining and viewing the location of the distal tip portion of laser enhanced transluminal angioplasty catheter 11, and also) in certain instances, may be utilized to locate the position of the distal tip of the optical fiber portions in those systerns wherein the optical fibers may ext~nd beyond the dis-tal tip of the cathet~r sl~ev~ portlon, such as beyond 10 polyethylene sleevc portion IIA.
In order to protect the surface of ~iber or fibers 3S, a buffer sheath may be utilized to encapsulate or coat the outer surface.
Typically, this buffer layer may be one or more fllms or layers o~ a polyarnide material, an~l rnay, in certaln instances, contain a UV rnarker 15 additive. Also, in certain applications, it may be deslrable to provide an inner buffer film or layer or the polyethylene sleeve portlon IIA. Such rnaterlal may be formed of a compatible polymeric rnaterial such as an epoxy material or the llke. It may be deslrable, In certain instances, to provide this Inner film or layer with a UV marI<er. 20 Wlth attentlon beinK dlrccted to Figure 3, and because of limitatlons of dra~tsrnanship, the Inclivid-Icll rnulti-laycr arr~rlecments ar~
illustrated In fragmentciry cut-away form.
As illustrated In l~igure 1, reflecte~l IlKht from optically reactlve and rcsponsive clement 37 is reElected frorn surface 31A of beam splltter 25 (diclIrolc fllter) 31 and through InterfererIce fllter S0 and through focuslng lens 67 and Into detector elemeIlt 4I. TI1e output of threstlold detector 53, as prevlously indicated In connection wltll the embodlment oE Flgure 1, provides inputs to electromecllarllcal shutter 26 as well æs to power supply 15B, such as at the second control input 15D to power supply 15B. 30 26~7~

As an alternate layout for the system, beam energy from the laser unlt may be passed directly onto a bearn spll ttor, wlth flrst and second detectors belng employed to dcllver sl~nals to the control rnonltor, such as an electromechanical shutter system. On the catheter skle of the beam splitter, a focusing lens is provided to carry the laser beam energy 5 into the input of a first optical fiber segment, whlch terminates through connectors into the control monitor. The output from the control rnonitor is, in turn, delivered into the second optical fiber se~ment, and thence into the distal tip end of the catheter unit. Such an arrangement provides an advantaKe of employlng one Icss aligllrnent mechanlsm, and elimlnates 10 certain lenses.
The laser enhanced transluminal angioplasty catheter device with the feedback system as disclosed hereln is advantageously utlllzed In such catheter devices, since it is hlghly reliable, and Is utilized wlthout need for additional fibers or wires in the catheter structure. 15 12 ;

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a laser enhanced transluminal angioplasty catheter system including a catheter having a proximal end and a distal end, a source of laser beam energy, lens means for focus-ing the laser beam energy from the source onto an optical fiber for providing a beam transmitting fiber column for transmission of laser beam energy from the proximal end of the distal tip end of the catheter, a control means interposed along said optical fiber at the proximal end of said catheter, said laser enhanced transluminal angioplasty catheter system being characterized in that (a) generator means are provided for generating a laser beam, an optical fiber column extending along the length of said catheter system for transmitting said laser beam to the distal tip of said catheter and for controllably discharging said laser beam from said catheter distal tip, a laser beam energy evalua-tion zone at the proximal end of said catheter system between said generator means and said distal tip, and means for accessing at least a portion of said laser beam within said beam energy evaluation zone during operation of said laser generator and said catheter system; (b) said beam transmitting fiber column includ-ing means for delivering laser beam energy from said column to said laser beam evaluation zone; (c) shutter means within said beam energy evaluation zone having means for controllably inter-rupting the passage of laser beam energy through said beam energy evaluation zone and along said beam transmitting fiber column upon detection of an anomalous signal; (d) beam splitter means disposed within said beam energy evaluation zone for diverting a portion of said laser beam energy passing through said beam energy evaluation zone for directing said diverted portion onto a first detector means, and means for simultaneously enabling the passage of the non-diverted portion of said laser beam energy through said beam splitter means and along said beam transmitting fiber column to said distal tip; (e) optically reactive means disposed at the distal tip of said catheter along the path of the non-diverted portion of said laser beam energy and axially dis-tally of said optical fiber column for normally receiving and normally transmitting substantially all of said non-diverted laser beam energy therethrough, and having optically reactive responsive means incorporated therein for generating radiant energy at a wavelength significantly different from that of said laser beam energy while being stimulated with said laser beam energy transmitted along said beam transmitting fiber column and received by said optically reactive means; (f) means for simulta-neously transmitting said stimulated radiant energy from said optically reactive means as an energy source through said optical fiber column and thence onto said beam splitter means for diver-sion of said stimulated radiant energy onto a second detector means during the operation of said laser beam generator and with said beam transmitting fiber column simultaneously transmitting laser beam energy from said generator means to said optically reactive means; (g) first and second signal processing means responsive to said first and second detector means respectively;
and (h) shutter control means responsive to the output of said first and second signal processing means for closing said shutter means and interrupting the passage of laser beam energy from said generator means through said beam energy evaluation zone upon detection of an anomalous signal from one of said first and second detector means.

2. The laser enhanced transluminal angioplasty catheter system as defined in claim 1, being particularly charac-terized in that said beam splitter means is a dichronic filter arranged for maximum transmission of incident laser beam energy.

3. The laser enhanced transluminal angioplasty catheter system as defined in claim 1, being particularly charac-terized in that said optically reactive means is a fluorescent lens element which emits fluorescent energy upon stimulation by laser beam energy.

4. The laser enhanced transluminal angioplasty catheter system as defined in claim 3, being particularly charac-terized in that said fluorescent lens element contains a dopant and is arranged to fluoresce and emit fluorescent energy at a wavelength greater than that of the incident laser beam energy.

5. The laser enhanced transluminal angioplasty catheter system as defined in claim 1, being particularly charac-terized in that said optical fiber column is arranged in first and second spaced apart fiber optical segments, and a beam energy evaluation zone is interposed between said first and second spaced apart fiber optical segments.