APPARATUS AND METHOD FOR REDUCING LASER BEAM ATTENTUATION IN A LIQUID MEDIUM

• US 20170354464A1
• Filed: 06/06/2017
• Published: 12/14/2017
• Est. Priority Date: 06/09/2016
• Status: Active Grant

• Current Assignee: Lumenis Limited (Boston Scientific Corporation)
• Original Assignee: Lumenis Limited (Boston Scientific Corporation)
• Inventors: Waisman, Tal, Khachaturov, Arkady, Preiss, Assaf
• Granted Patent: US 9,895,196 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 17/22 Implements for squeezing-off ulcers or the like on the inside of inner organs of the body; Implements for scraping-out cavities of body organs, e.g. bones; Calculus removers; Calculus smashing apparatus; Apparatus for removing obstructions in blood vessels, not otherwise provided for dilators A61M29/00
• CPC Class Codes: A61B 17/22004 using mechanical vibrations, e.g. ultrasonic shock waves A61B17/225 takes precedence
• CPC Class Codes: A61B 18/20 using laser
• CPC Class Codes: A61B 18/22 the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor
• CPC Class Codes: A61B 18/26 for producing a shock wave, e.g. laser lithotripsy
• CPC Class Codes: A61B 2017/00017 Electrical control of surgical instruments
• CPC Class Codes: A61B 2017/00176 Two pulses, e.g. second pulse having an effect different from the first one
• CPC Class Codes: A61B 2017/00482 with a code
• CPC Class Codes: A61B 2017/22007 Cavitation or pseudocavitation, i.e. creation of gas bubbles generating a secondary shock wave when collapsing
• CPC Class Codes: A61B 2018/00625 Vaporization
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00684 using lookup tables
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/20554 Arrangements for particular intensity distribution, e.g. tophat
• CPC Class Codes: A61B 2018/263 the conversion of laser energy into mechanical shockwaves taking place in a liquid

Abstract

A method of optimizing the irradiation of a target with laser radiation includes selecting and mounting on a laser radiation delivery device either a waveguide or optical fiber type to be used; also, selecting at least the following parameters: selecting the total energy of the at least one train of pulses to be delivered to the target, and selecting the distance from the distal delivery end to the target; then, initiating irradiation of the target for the at least one train of pulses by generating a first laser pulse with sufficient energy (Eⁱ) to form a vapor bubble in a liquid medium; allowing the vapor bubble formed to expand an amount sufficient to displace a substantial portion of the liquid medium from the space between the distal delivery end and the target; and, thereafter, after the selected time delay (T^d) sufficient for the formed vapor bubble to reach its optimum extent, generating a second laser pulse (E^p), the second laser pulse being delivered to the target through the formed vapor bubble.

Claims

1. A method of optimizing the irradiation of a target with laser radiation, wherein the laser radiation is associated with a laser radiation delivery device and the laser radiation is delivered to the target by one of a waveguide or an optical fiber, the waveguide and the optical fiber each having a distal delivery end, wherein the distal delivery end is spaced from the target, wherein the space between the distal delivery end of the guide and the target is occupied by a liquid medium, and wherein the laser radiation is delivered along a light path in at least one train of laser pulses of a wavelength which is at least partially absorbed in the liquid medium, the at least one train of pulses having a first laser pulse and a second laser pulse, said method comprising the steps of:

selecting and mounting on the laser radiation delivery device a waveguide or optical fiber type to be used in irradiating the target;

selecting at least the following parameters;

selecting the total energy of the at least one train of pulses to be delivered to the target, and selecting the distance from the distal delivery end to the target;

further comprising a controller which controls the laser radiation delivery device and implements the steps of selecting the total energy delivered by the laser radiation delivery device and selecting the distance from the distal delivery end to the target;

initiating irradiation of the target for the at least one train of pulses by generating the first laser pulse with sufficient energy (Eⁱ) to form a vapor bubble in the liquid medium at the distal delivery end;

allowing the vapor bubble formed to expand an amount sufficient to displace a substantial portion of the liquid medium from the space between the distal delivery end and the target;

thereafter, after the selected time delay (T^d) sufficient for the formed vapor bubble to reach its optimum extent, generating the second laser pulse (E^p), the second laser pulse being delivered to the target through the formed vapor bubble, thereby minimizing the laser radiation absorbed by the liquid medium and optimizing the laser radiation reaching the target;

the controller further comprising a memory including a lookup table, the lookup table including a plurality of parameters including Eⁱ, E^p and T^d, and wherein the steps of selecting the waveguide or optical fiber type, selecting the total energy to be irradiated and selecting the distance from the distal delivery end to the target causes the controller to access the lookup table to select corresponding parameters for Eⁱ, E^p and T^d and too generate and deliver laser radiation with the selected parameters for Eⁱ, E^p and T^d.

2. The method of claim 1, wherein the ratio of Eⁱ/E^p is from 10:

1 to 1;

10.

3. The method of claim 1, wherein the at least one train of pulses comprises two pulses.

4. The method of claim 1, wherein the at least one train of pulses comprises greater than two pulses.

5. The method of claim 1, wherein the at least one train of pulses is more than one train of pulses and the step of selecting comprises the further step of selecting a repetition rate for delivery of the more than one train of pulses.

6. The method of claim 5, further comprising the steps of:

measuring the actual energy irradiated by the laser;

comparing the actual measured energy to the total selected energy; and

, if the comparison demonstrates variance of the actual measured energy from the selected total energy, adjusting one or more of the selected parameters for any following train of pulses to achieve the selected energy delivered to the target.

7. The method of claim 1, wherein the target is a tissue, an organ or a formed stone within a human body.

8. The method of claim 1, wherein the lookup table comprises one or more datasets containing optimized values of Eⁱ, E^p and T^d for a plurality of waveguide or optical fiber types and distances from the distal delivery end to the target, and wherein the step of selecting a waveguide or optical fiber type causes the controller to access the lookup table to determine the optimal values of Eⁱ, E^p and T^d.

9. The method of claim 1, wherein the type of waveguide or optical fiber type includes at least one of the parameters of:

fiber diameter, fiber material, fiber numerical aperture and shape of the distal delivery end.

10. The method of claim 1, wherein the step of selecting the distance from the distal delivery end to the target includes the further step of measuring the distance and selecting the measured distance.

11. The method of claim 6, wherein the step of measuring the actual energy delivered by the laser is performed by a photodetector in the light path of the laser radiation.

12. The method of claim 6, wherein the step of adjusting the one or more parameters is accomplished by a closed loop feedback circuit operatively connected to the controller.

13. The method of claim 9, wherein the step of selecting the waveguide or optical fiber type includes the further step of mounting the waveguide or optical fiber onto the delivery device, and wherein the device automatically recognizes the parameters of the waveguide or optical fiber.

14. The method of claim 13, wherein the step of automatically recognizing is performed by a RFID identification tag mounted on the delivery device and on the waveguide or optical fiber.

15. The method of claim 9, wherein the controller indicates on a user interface associated with the controller whether or not the waveguide of optical fiber type is compatible with the one or more parameter selected.

16. The method of claim 1, wherein the at least one train of pulses includes one or more of:

more than one Eⁱ and more than one E^p.

17. The method of claim 1, wherein the controller controls the laser radiation delivery device and implements the steps of selecting the total energy delivered by the laser radiation delivery device and selecting the distance from the distal delivery end to the target based on the waveguide or optical fiber type mounted on the delivery device.

18. A method of irradiating a target with laser radiation, wherein said radiation is delivered to the target by a guide having a delivery end, and wherein the delivery end is spaced from the target, and wherein the space between the delivery end of the guide and the target is occupied with a liquid medium, and wherein the laser radiation has a wavelength which is absorbed in the liquid medium, said method comprising the steps of:

generating a first laser pulse having sufficient energy to form a vapor bubble in the liquid medium at the delivery end of the guide; and

generating a second laser pulse a predetermined time after the first laser pulse, said predetermined time being selected to allow the vapor bubble to expand an amount sufficient to displace a substantial portion of the liquid medium from the space between the delivery end of the guide and the target so that said second laser pulse may be delivered to the target through the vapor bubble thereby minimizing the laser radiation absorbed by the liquid medium and maximizing the laser radiation reaching the target.

19. A medical laser system for treating tissue with a laser beam, said tissue being immersed in a liquid medium formed primarily of water, said system comprising:

a solid state gain medium generating an output wavelength between 1.0 and 10.6 microns;

a flashlamp for exciting the gain medium to generate a laser beam;

an optical fiber for guiding the laser beam from the gain medium to the tissue, said fiber having a delivery end positioned close to but spaced from the tissue to be treated; and

a controller for controlling the flashlamp and functioning to sequentially generate a series of first and second laser pulses, wherein each said first laser pulse has an energy sufficient to form a vapor bubble in the liquid medium at the delivery end of the fiber and wherein each said second laser pulse is generated a predetermined time after the first laser pulse, said predetermined time being selected to allow the vapor bubble created by the first laser pulse to expand an amount sufficient to displace a substantial portion of the liquid medium from the space between the delivery end of the fiber and the tissue so that said second laser pulse may be delivered to the tissue through the vapor bubble thereby minimizing the laser radiation absorbed by the liquid medium and maximizing the laser radiation reaching the target.