Method of cutting material for use in implantable medical device

Abstract

A method of cutting material for use in an implantable medical device employs a plotted laser cutting system. The laser cutting system is computer controlled and includes a laser combined with a motion system. The laser precisely cuts segments out of source material according to a predetermined pattern as designated by the computer. The segments are used in constructing implantable medical devices. The cutting energy of the laser is selected so that the cut edges of the segments are melted to discourage delamination or fraying, but communication of thermal energy into the segment beyond the edge is minimized to avoid damaging the segment adjacent the edge.

Description

RELATED APPLICATIONS

This application is a

For the above embodiment, the laser energy per pulse is about:
(7.5 joules/second)/((1 inch/second)×(1,000 pulses/inch) )=0.0075 joules/pulse.

Other materials, such as bovine or other kinds of pericardium tissues and laminar materials can also be advantageously laser cut with a CO₂ laser as discussed above. In another preferred embodiment wherein such materials, including equine pericardium, are laser cut, about 0.005-0.5 joules of laser energy are supplied per pulse, with a laser spot size of about 0.002 to 0.005 inches in diameter, a cutting speed of about 1 inch/second, and a pulse rate of about 1,000 PPI. More preferably, about 0.005-0.02 joules of laser energy are supplied per pulse. For the Universal Laser Systems M-series laser discussed above, the following sample settings enable laser cutting within the above-discussed parameters: a 1.5 Lens, 20% power setting, 3.4% speed, 1,000 PPI and 1,000 dots per inch.

It is to be understood that if parameters such as the pulse rate and cutting speed are adjusted, corresponding adjustments to other parameters can be made so that the energy imparted to the material substantially stays within the desired parameters. In this manner, a generally uniform weld can be formed along a cut edge without discoloring the edge or imparting excessive heat to other portions of the segment.

It is also to be understood that other types of lasers, such as an erbium laser that generates a laser beam having a wavelength of about 2.7-3.0 μm, can suitably be used to cut segments. Such alternative lasers can be operated at settings so that the cut edges are welded as discussed above.

Alternative techniques may be employed for laser cutting of segments for use in prosthetics, such as disclosed in U.S. Patent Application Publication No. US 2002/0091441, which was published on Jul. 11, 2002. The entire disclosure of this publication is hereby incorporated herein by reference.

Various types of tissue and man-made materials can be cut with a laser by using generally the same principles as discussed above. For example, other types of laminar tissue can be cut so that the cut edges are welded and have a generally uniform consistency with little or no discoloration. Similarly, for man-made materials such as woven or knitted polymers, the cut edges preferably are melted so that fraying of the woven filaments or yarns is minimized or avoided, but discoloration is also avoided.

With reference next to FIG. 9, an embodiment of a laser cutting apparatus for cutting curved or tubular materials is illustrated. This embodiment is substantially similar to the embodiment presented in FIG. 6 except that the support surface 80 comprises a rotary axis 104 configured to accept a tubular source material 106. In addition to vertical movement about a Z-axis, the rotary axis 104 is adapted to rotate in order to help position the tubular source material 106 in an advantageous cutting position relative to the focused laser beam 88.

Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while a number of variations of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed invention. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.

Claims

1. A method of creating an implantable medical prosthesis, comprising:

a. providing a sheet of pericardium, wherein the pericardium has at least two tissue layers;

b. supporting the sheet of pericardium with a support platform;

c. providing a laser cutting apparatus having a laser tube assembly configured to create a laser beam which is directed through a series of optical elements to direct a laser beam on the support platform; and

d. cutting a segment of tissue out of the sheet of pericardium with a laser beam; said cutting comprising operating the laser apparatus at a power and pulse rate such that said laser beam welds the layers of the pericardium together along a laser cut edge

wherein sufficient energy is imparted to vaporize portions of the pericardium along the cut edge and to at least partially melt the cut edges without substantial burning of the pericardium adjacent the cut edge and further wherein the cut edge of the tissue segment is not susceptible to premature wear.

2. The method of claim 1, wherein the pericardium tissue comprises equine pericardium.

3. The method of claim 1, wherein the laser beam power and pulse rate are selected so that there is substantially no discoloration of the pericardium along the cut edge.

4. The method of claim 1, wherein the prosthesis comprises a heart valve, said cutting comprising cutting a plurality of segments of tissue out of the sheet of pericardium with the laser beam and attaching the cut segments to one another to form the valve.

5. A method of creating an implantable medical prosthesis, comprising: providing a sheet of pericardium, wherein the pericardium has at least two tissue layers; and cutting a segment of tissue out of the sheet of pericardium with a laser beam; said cutting comprising operating a laser at a power and pulse rate having the following parameters: 1.5 lens, 20 percent power setting, 3.4 percent speed, 1,000 pulses per inch and 1,000 dots per inch, such that said beam welds the layers of the pericardium together along a laser cut edge without significantly burning the pericardium adjacent the cut edge.

6. The method of creating an implantable medical prosthesis of claim 1 further comprising providing a motion system to selectively locate and move the position of the laser beam relative to the pericardium tissue.

7. The method of claim 6 further comprising providing an electronic mechanism that changes the relative position of the support platform and the beam.

8. The method of claim 7 wherein the motion system actuates the electronic mechanism to adjust the relative position of the laser beam.

9. The method of claim 7 wherein the electronic mechanism is connected to the laser beam to move the laser beam relative to the support platform.

10. The method of claim 6 wherein the motion system comprises a digital processor connected to the electronic mechanism for selecting cutting patterns.

11. The method of claim 10 wherein the digital processor further comprises a computer assisted design software program.

12. The method of claim 11 wherein the computer assisted design software program further comprises a template.

13. The method of claim 1 wherein the optical components further comprises lenses.

14. The method of claim 1 wherein the optical components further comprises mirrors.

15. The method of claim 1 further comprising operating the laser in a pulsed manner and supplying from about 0.005 of laser energy per pulse to about 0.5 joules of laser energy per pulse.

16. The method of claim 15 further comprising operating the laser to produce a laser spot size of from about 0.002 inches in diameter to about 0.005 inches in diameter.

17. The method of claim 1 further comprising operating the laser at a cutting speed of about 1 inch per second.

18. The method of claim 15 wherein operating the laser in a pulsed manner comprises supplying a pulse rate of about 1000 pulses per inch.

19. The method of claim 1 further comprising operating the laser at a wavelength of about 10.6 microns.

20. The method of claim 1 further comprising operating the laser at a wavelength of from about 2.7 microns to about 3.0 microns.

21. The method of claim 3 wherein the laser energy selected is about 0.0075 joules per pulse and a laser spot diameter of about 0.003 inches.