WO1995024867A1

WO1995024867A1 - Laser energy concentration in laser powered surgical instrument

Info

Publication number: WO1995024867A1
Application number: PCT/US1995/003306
Authority: WO
Inventors: Jack M. Dodick
Original assignee: Dodick Jack M
Priority date: 1994-03-15
Filing date: 1995-03-15
Publication date: 1995-09-21

Abstract

A surgical instrument in the form of a needle has a distal port for receiving tissue. An optical fiber extends along the length of the needle and has its distal end positioned in a distal chamber of the needle. The chamber is in communication with the port. Pulses of laser energy are delivered to the distal end of the optical fiber. A small lens at the distal end of the optical fiber concentrates the pulses of laser energy to a focal point within the chamber. The chamber is normally filled with saline. The laser energy is sufficiently great and the focal zone is sufficiently small so that the focused laser energy produces plasma at the focal point from the saline in the chamber. The generation of plasma creates shockwaves that travel through the saline in the chamber and strike and fracture tissue which is held at the tissue receiving port. The inner wall of the chamber is a spherical segment. It also receives shockwaves. The wall reflects and because of its curvature concentrates those shockwaves at the tissue receiving port thereby providing an additional shockwave for fracturing tissue held at the port. Fractured tissue together with irrigating fluid is drawn out through an aspirating passageway.

Description

LASER ENERGY CONCENTRATION IN LASER POWERED SURGICAL INSTRU_MENT

Reference To Related Applications

This application is a continuation-in-part of co-pending patent applications filed by applicant in the fc United States Patent Office as Serial No. 07/844,661 on April 8, 1992 as a National Phase of a PCT case which in turn in a 5 continuation-in-part of Serial No. 07/426,971 filed on October 25, 1989, entitled: Laser Powered Surgical Instrument and Serial No. 07/429,121 filed on October 30, 1989 entitled: Surgical Instrument With Input Power Collector.

10 Background Of The Invention

This invention relates in general to a laser powered surgical instrument and more particularly to a technique for generating plasma from input laser pulses wherein the plasma creates Shockwaves that are used to fracture tissue positioned

15 or held at an opening near the distal end of the surgical instrument.

An instrument described in U.S. Patent Application Serial No. 07/844,661 employs a target which receives the laser pulses. The laser pulses at the target material forms a plasma

20 in response to each laser pulse. Accordingly the target gradually wears away. One application of the instrument is for the removal of a cataract. More than one thousand pulses may be

, required for each operation. The target has to be sufficiently thick so that it will withstand the large number of pulses * 25 required for the operation and yet have target material present in the path of the laser pulses at the end of the operation. It is important that the laser pulses never impinge directly on tissue. There is too much risk of damage to tissue if such occurs.

Accordingly, it is a major purpose of this invention to provide a technique for generating plasma from the laser pulses, so that Shockwaves will in turn be developed, in a fashion that assures isolation of the laser pulses from tissue of the patient involved.

It is a further purpose of this invention that this isolation of laser pulses from tissue be in the context of a small diameter probe which will make a minimum size incision and which will provide a combined function of directing Shockwaves to the tissue to be fractured, and adequately aspirating the tissue as it is fractured.

Brief Description

A surgical instrument in the form of a two mm diameter needle has a distal port for receiving tissue. An optical fiber extends along the length of the needle and has its distal end positioned in a distal chamber of the needle. The chamber is filled with saline and is in communication with the port. Pulses of laser energy are delivered to the distal end of the optical fiber. Neodymium-YAG laser pulses of, for example, 20 nano¬ seconds width and 15 illi-joule energy per pulse at a rep. rate of 10 pulses per second are provided. A lens having a very short focal length of, for example, 0.5 mm is connected to the distal end of the optical fiber. The lens concentrates the pulses of laser energy to a focal point within the chamber. The laser energy is sufficiently great and the focal zone is sufficiently small so that the focused laser energy produces plasma at the focal point from the saline in the chamber. The generation of plasma creates Shockwaves that travel through the saline to the port where they strike and fracture tissue held at the port. A partially spherical concave inner wall of the chamber also receives Shockwaves. This wall reflects and because of its curvature concentrates those Shockwaves at the port thereby providing an additional Shockwave for fracturing tissue held at the port. Fractured tissue together with irrigating fluid

(saline) is drawn out through an aspirating passageway.

Brief Description Of The Drawings

FIG. l is a longitudinal cross-section of an embodiment of the present invention. FIG. 2 is a block diagram illustrating the use of a pulsed laser generator to provide the input energy to the fiber optic element of the surgical instrument.

Description of The Preferred Embodiments

With reference to FIG. 1, a surgical probe 10 of this invention has a tubular outside wall 12 with an outer diameter of approximately 2 millimeters (2 mm) and a wall thickness of approximately 0.25 mm. Within wall 12 there is an inner tubular wall 14 that also has a wall thickness of about 0.25 mm.

Passageway 16 permits infusion of saline through the wall opening 18 into the operating area. Passageway 20 is an aspirating passageway. Fractured tissue and fluid are drawn in through the front port 22 and aspirated out through the passageway 20. A front wall 24 defines the distal end of the probe 10. An optical fiber 26 extends through the passageway 16 and has its distal end held in position by a opening in an insert 28. A lens 30 having a very short focal length is held in position by insert 28 at the distal end of optical fiber 26. Pulses of laser energy are delivered through optical fiber 26 and focused by lens 30 to a point P which is within chamber 32 at the distal end of probe 10. The laser energy that is focused by lens 30 is concentrated into a very small zone, sufficiently small so that the energy density required to create plasma from the saline is attained. Although the focus is into such a zone, that zone will be called a point P herein because it is such a small zone. It should be understood that the point P is not a geometric point, but a relatively small three dimensional zone.

The focusing of these laser pulses at point P creates such an intense concentration of energy that the saline at the point P in the chamber 32 forms a plasma. The plasma formation generates a Shockwave that travels through the liquid medium (essentially saline) that fills chamber 32 at the distal end of probe 10. The Shockwave impinges on any tissue that is held at port 22 and causes tissue that is positioned there to fracture. Fractured tissue is aspirated through passageway 20.

The insert 28 has a fairly complex structure and can, of course, be constituted by two or more inserts to the extent that such would facilitate fabrication and assembly. However, for present purposes the insert 28 can be considered a single insert. It has a proximal portion that is essentially cylindrical and serves to hold and position the laser fiber 26. It has a distal portion which includes the front wall 24 having a concave spherical inner surface 34. This spherical surface 34 is a portion of a sphere and extends around the axis of the fiber 26 down to approximately the line 36. The radius of curvature of this spherical segment 34 is such that the center of the radius falls approximately at the port 22. The spherical surface 34 will reflect that portion of a Shockwave that impinges on it toward the port 22 and because of the curvature tends to concentrate the reflected Shockwave at the port 22. In this fashion any shock provided by a reflected wave is maximized at the port 22 and serves to further fracture tissue held at the port 22.

The front wall 24 is important to shield tissue from direct laser energy and light. Not all laser energy will be focused at the point P and thus it is important that there be a wall directly in front of the distal end of the laser fiber 26.

Accordingly, it can be seen that what happens is that laser energy concentrated at point P generates a Shockwave which emanates spherically in all directions from the point P. The

Shockwaves travels to the point 22 at which tissue fracture occurs. It also travels out to contact the curved inner surface

34 where it is reflected. The reflected Shockwave is directed and concentrated at port 22 to provide a Shockwave that may further fracture any tissue held at the port 22.

In order to minimize damage to the wall 34 by the Shockwave generated at the point P, it is deemed advisable that the distance between the point P and the wall 34 be at least three times as great as the focal distance between the lens 30 and the point P. The quartz material of the fiber 26 and lens 30 are less subject to damage than is the stainless steel of the insert 28. The curved wall surface 34 is preferably a spherical segment, it is possible that optimum design will call for deviation from a spherical segment in order to accommodate other dimensional requirements of the instrument and in order to better position the point at which the reflected Shockwave energy is concentrated.

The creation of the plasma at point P generates a primary shock wave that travels out in all directions. The plasma necessarily collapses a short time after its creation. The collapse of the plasma generates a secondary shock wave. The secondary shock waves have a much smaller magnitude than the primary shock waves. As a result, the secondary shock waves are unimportant for the present invention.

The reflected shock wave could serve to substantially reduce the magnitude of the primary shock wave created by the next successive pulse. The dimensions of the chamber 32 and the position of the focal point P should be selected to minimize this cancellation effect.

The laser used to provide laser pulses is a Neodymium- YAG pulsed Q switched laser 30. It provides laser energy with a wavelength of 1,064 nano-meters. The laser energy provides pulses having a duration which ranges between two and thirty nano-seconds. Each pulse has energy between five and twenty milli-joules. The optimum trade-off between pulse waves and pulse energy depends upon how well the particular pulse can be focused. Accordingly, a twenty nano-second pulse width having five milli-joules of energy which is well focused could provide a better result than a fifteen nano-second pulse width with 5 twenty milli-joules of energy which is not as well focused. The pulses have a pulse repetition rate of approximately five to twenty pulses per second. Thus, the energy provided is between one-hundred milli-joules per second and four-hundred milli-joules per second.

10 The smaller the diameter of optical fiber 26, the smaller the angle of dispersion at its distal end and the more effective lens 30 will be to focus the energy to a concentration sufficient to create plasma. The presently preferred laser fiber 26 is one that has a 320 micron core and an overall 400 micron

15 diameter. To generate plasma in saline or water so that Shockwave formation is effected, a power density of about 2.0 to 2.1 times 10⁸ watts per square centimeter is required. This requires that the pulses transmitted to the distal end of laser fiber 26 be focused to a very small zone. There is likely to be

20 a trade-off between pulse width and pulse energy to provide an optimum focus.

Lens 30 can be a micro lens known as a Selfoc® lens. Such a lens is available from SG America, Inc. of Som erset, New Jersey. A focal length of 0.5 mm is a useful focal length. A

25 plano-convex lens would be the preferred lens to use.

Alternately, lens 30 can be created by heating the

' distal end of an optical fiber to form a ball at the distal end. Such a ball can operate as a lens to focus the pulses of laser energy to a concentration sufficient to generate the plasma in the saline. One technique of creating this ball is to employ a carbon dioxide laser to provide laser energy at the distal end of the fiber. This energy will collect at the distal end of the fiber so as to melt the quartz of the laser fiber. However, this has to be done in a controlled fashion and, although applicant has created such a ball focal arrangement by examining the distal end of the fiber through a microscope as the laser - energy supplied builds up, applicant has not yet determined a technique where this can be practically done on a large scale basis.

The cylindrical walls 12 and 14 and the insert 28 are all preferably made of stainless steel.

Claims

What is claimed is:

1. A surgical needle for fracturing tissue comprising: a tubular sidewall having a longitudinal axis and a distal end portion, a distal end wall connected to said tubular side wall, said end wall and said distal end portion of said sidewall defining a chamber, a laser fiber extending longitudinally to said chamber, said laser fiber having a longitudinal axis and a distal end, a lens at the distal end of said laser fiber to focus laser energy to a predetermined focal zone within said chamber said zone being sufficiently small to provide a concentration of energy in said zone sufficiently great to create plasma from whatever fluid is in said chamber, said distal end portion of said sidewall having a tissue receiving port and a tissue receiving zone adjacent to said port, said tissue receiving port and said tissue receiving zone being radially displaced from said longitudinal axis of said laser fiber, said production of plasma at said focal zone producing Shockwaves that are propagated to said tissue receiving zone, laser energy from said laser fiber having a path that is displaced from said tissue receiving zone, and an aspirating passageway extending longitudinally within said sidewall and in communication with said tissue receiving zone.

2. The surgical needle of claim 1 wherein: said chamber includes a curved segment to reflect Shockwaves generated at said focal zone and to concentrate the reflected energy at said tissue receiving port.

3. The surgical needle of claim 1 wherein said focal zone is at least three times as far from any portion of the wall of said chamber as it is from said lens.

4. The surgical needle of claim 2 wherein said focal zone is at least three times as far from any portion of the wall of said chamber as it is from said lens.

5. The method for surgically removing tissue comprising the steps of: drawing tissue into a tissue receiving zone of a surgical needle, providing a liquid media in a chamber that includes said tissue receiving zone, providing pulses of laser energy to said chamber, focusing said pulses of laser energy to a focal zone displaced from said tissue receiving zone, said focal zone being small enough so that the energy concentrated at said focal zone will produce plasma in said liquid media and therefore produce Shockwaves within said liquid media, propagating said Shockwaves through said liquid media to the tissue to be fractured in said tissue receiving zone and thereby fracturing the tissue, (Claim 5 con ' t)

aspirating the fractured tissue out of an aspirating passageway in communication with said tissue receiving zone, and providing irrigation to an area outside of said surgical needle to assist said step of aspirating.

6. The method of claim 5 further comprising the steps of: reflecting said Shockwaves from a curved wall of said chamber and concentrating said reflected Shockwaves at said tissue receiving zone.