fig1 illustrates a balloon catheter 10 having an elongated catheter shaft . 11 having a proximal end 12 and a distal end 13 , an inflatable balloon 14 on a distal section proximal to the distal end of the catheter shaft , an adapter 16 mounted on the proximal end 12 , and at least one recess 17 formed in a wall of the shaft 11 by application of laser radiation . one significant benefit of using a uv laser to form the recess 17 is that a recess with a smooth surface is formed without increasing the shaft diameter or otherwise mechanically or thermally affect adjacent polymeric materials . because the material is not physically pushed or melted during the removal , the increase in the shaft diameter which is , caused by physical displacement of material or beading of melted material is avoided . by controlling the removal of material , the method of the invention provides a means of precisely and repeatably affecting the flexibility and strength along a region of the shaft axis . in the embodiment shown in fig1 the shaft 11 comprises an outer tubular member 20 and an inner tubular member 21 disposed within the outer tubular member , and defining , with the outer tubular member , inflation lumen 22 in fluid communication with the balloon interior . the inner tubular member 21 has an outer surface 23 and a distal end 24 and an inner lumen 25 extending distally to a port 27 in the distal end to the balloon . guidewire 28 is slidably disposed within a lumen of the inner tubular member 21 . the pattern , density , area and location of the material removed affects the flexibility and compressive strength of the catheter shaft 11 , and are therefore chosen based on the desired shaft performance characteristics . the recess 17 may form grooves , or pits or depressions in the shaft , and in various patterns including continuous or multiple spirals , rings , and semi - circles , and the like . in the embodiment illustrated in fig2 the recess 17 forms a continuous spiral 26 in the shaft 11 . fig5 illustrates an alternative embodiment of the invention in which the recess 17 forms multiple pits 32 in the outer surface of the catheter inner tubular member 21 . additionally , recess may form tapering in shaft outer diameter , and preferably a tapered distal tip 19 , as illustrated in fig2 . the uv laser radiation allows for recess sizes from about 0 . 25 μm to about several square centimeters , and for non - uniform dimensioned areas such as 0 . 05 mm × 0 . 5 mm ( 0 . 002 × 0 . 02 inch ). the width of the recess in the wall of the shaft is typically about 0 . 25 μm to about 1 . 0 mm , and the depth of the recess into the shaft wall is typically about 0 . 25 μm to about 0 . 5 mm . the presently preferred laser power ranges from about 10 mj to about 20 mj , and the pulse rate ranges from about 10 pps to about 100 pps . in one example , the invention comprises a balloon catheter with a flexible distal section formed by a recess 17 on a distal portion of the inner tubular member . preferably , the recess 17 is located from a point proximal to the distal end of the balloon , and extending toward , and possibly up to , the distal end of the shaft . the length of the catheter is generally from about 90 cm to about 150 cm . typically , in forming a flexible distal shaft section or a tapered , distal end , the recess extends along a section of the catheter ranging from about 1 . 5 mm to about 7 mm in length , and preferably about 2 to about 6 mm in length . the length of the section will vary depending on the degree of flexibility desired in the catheter . in the method of the invention , a catheter having a polymeric elongated shaft 11 with a flexible section 18 is manufactured by a method comprising , forming at least one recess 17 in the shaft by applying laser radiation of an ultraviolet wavelength to an outer surface of the shaft to remove shaft material . the uv laser radiation may remove material both axially and radially from a catheter shaft 11 . fig6 and 7 illustrates laser energy 31 being applied by laser 30 to the catheter shaft 11 . as best illustrated in fig8 showing a transverse cross - sectional view of a catheter shaft 11 , the laser radiation 31 may be applied transverse to the shaft to form grooves or pits in the shaft 11 . as illustrated in fig6 and 7 , the transversely applied laser radiation may be applied perpendicular relative to the shaft longitudinal axis or at an acute angle relative to the shaft . the acute angle is typically about 10 ° to about 80 ° relative to the shaft . alternatively , as illustrated in fig9 the laser radiation may be applied tangentially to the shaft , to form a tapered distal section or form a shaft outer diameter concentric with an inner diameter by correcting nonuniformity in the shaft outer diameter . to form a tapered distal section , the laser is moved at an angle relative to the shaft longitudinal axis to remove an increasing amount of shaft material . fig1 illustrates formation of a tapered distal tip , with the radiation focus tangential to the catheter shaft and moved longitudinally relative to the shaft at an angle to the shaft axis . the relative movement between the catheter and the laser is typically achieved by moving the catheter about a fixed laser . while the laser wavelength is preferably within the ultraviolet region , within that region , the longest wavelengths are less absorptive and therefore less effective and shortest wavelengths are generally more difficult to produce , requiring very specific optics . the presently preferred wavelengths are from about 190 nm to about 360 nm , and most preferably are selected from the group consisting of 248 nm , 266 nm , and 355 nm . lasers used in the invention must be able to produce radiation in the uv region . suitable lasers include a pulsed excimer laser , such as a krf , xef , krci , xeci or xebr laser , and non - linear harmonic crystals optically pumped by a laser with an output that is continuous wave , pulsed , q - switched , or modulated . the presently preferred laser source is an excimer laser or a nd / yag laser . selection of the wavelength within the ultraviolet region and the appropriate optical set - up for imaging the laser beam on the catheter shaft allows precise control over the removal of material in a selected area or pattern . while the present invention has been described herein in terms of certain preferred embodiments , modifications and improvements may be made to the invention without departing from the scope thereof . for example , while the formation of a gradual taper in the catheter shaft distal end was described , the method of the invention could also be used to form abrupt stepped down sections in a catheter shaft . additionally , while the invention is described herein in terms of an inner and outer membered balloon catheter , it should be understood that the invention is not limited to use with balloon catheters , or catheter designs having inner and outer shaft members .
a method of forming a catheter shaft having a flexible section by selective removal of catheter shaft material using laser radiation , and a catheter produced therefrom . the laser radiation is of an ultraviolet wavelength . the catheter shaft is made more flexible without a disadvantageous decrease in column strength by operating the laser in the uv , which allows for machining recess patterns with smooth and repeatable recess surfaces while producing little or no thermal or mechanical effects on the remaining adjacent polymeric material .