Patent Grant
7186246
The present invention relates to a catheter, and more particularly, to a catheter having an ultrasound assembly.
Many medical treatments can be performed using catheters with an ultrasound transducer. These ultrasound transducers deliver ultrasound energy to a target site within a patient. The ultrasound energy can provide a therapeutic effect by itself or can enhance the effects of other therapeutic media exposed to the ultrasound energy. Inefficient ultrasound transducer arrangements can generate excessive heat during a medical treatment.
The invention relates to a catheter system. The system comprises a catheter body having a chamber containing a low acoustic impedance medium. The catheter body includes an elongated body with an external surface and an ultrasound transducer having an external side between a first end and a second end. The ultrasound transducer is positioned over the external surface of the elongated body such that the first end of the ultrasound transducer is adjacent to the chamber.
Another embodiment of the system comprises a catheter body having an external surface. The catheter body includes an ultrasound transducer having a side between a first end and a second end. A first medium is positioned adjacent to the first end of the ultrasound transducer and a second medium is positioned adjacent to the external side of the ultrasound transducer. The second medium is harder than the first medium to encourage flexibility of the catheter body adjacent to the first end of the ultrasound transducer and efficient transmission of ultrasound energy from the external side of the ultrasound transducer.
The catheter system can also include a sheath for receiving the catheter.
The invention also relates to a method for forming a catheter. The method includes positioning an ultrasound transducer over an external surface of an elongated body and positioning a collar over the external surface of the elongated body such that at least a portion of the collar is spaced apart from the ultrasound transducer. The method also includes positioning a transducer sheath over at least a portion of the ultrasound transducer and over at least a portion of the collar to form a chamber between the ultrasound transducer and the collar.
Another embodiment of the method includes positioning a first spacer over an external surface of an elongated body and positioning a member over at least a portion of the first spacer so as to form a chamber between the member and the external surface of the elongated body. The method also includes positioning an ultrasound transducer over the member.
Yet another embodiment of the method includes providing an ultrasound transducer having a side between a first end and a second end. The ultrasound transducer is positioned over an external surface of an elongated body. The method includes forming a first medium adjacent to the first end of the ultrasound transducer and forming a second medium adjacent to the side of the ultrasound transducer. The second medium is harder than the first medium to encourage flexibility of the catheter body adjacent to the first end of the ultrasound transducer and efficient transmission of ultrasound energy from the external side of the ultrasound transducer.
The invention relates to a catheter having a chamber containing a low acoustic impedance medium. The catheter can also include an elongated body with an external surface. An ultrasound transducer having an external side between a first end and a second end can be positioned over the external surface of the elongated body such that the first side of the ultrasound transducer is adjacent to the chamber.
The low acoustic impedance material within the chamber reduces the portion of ultrasound energy which is transmitted through the chamber. This reduction causes an increased portion of ultrasound energy to be delivered from the second end of the ultrasound transducer and/or from the external side of the ultrasound transducer. As a result, the ultrasound energy produced from these sections of the ultrasound transducer is delivered with a greater efficiency.
The ultrasound transducer can be positioned distally relative to the chamber in order to increase the efficiency of the ultrasound energy transmitted in the distal direction. Alternatively, the ultrasound transducer can be positioned proximally relative to the chamber in order to increase the efficiency of the ultrasound energy transmitted in the proximal direction.
Another embodiment of the catheter includes a chamber between the elongated body and an internal side of the ultrasound transducer. The chamber can include a low acoustic impedance medium to reduce the portion of ultrasound energy transmitted into the elongated body. As a result, the ultrasound energy produced from the ends and the external side of the ultrasound transducer is delivered with a greater efficiency than could be achieved without the chamber.
A catheter according to the present invention can include various combinations of the above chambers. Each of the chambers can be independent of one another or they can be in communication with one another. The chambers can contain a low acoustic impedance medium. For instance, a catheter can include a first chamber adjacent to the first end of the ultrasound transducer, a second chamber adjacent to the second end of the ultrasound transducer and a third chamber between the internal side of the ultrasound transducer and the elongated body. As a result, the ultrasound energy produced from the external surface of the catheter is delivered at an increased efficiency. Such a catheter efficiently delivers ultrasound energy from the side of the catheter.
As another example, a catheter can include the first chamber adjacent to the first end of the ultrasound transducer and the third chamber between the internal side of the ultrasound transducer and the elongated body. Further, the ultrasound transducer can be positioned distally relative to the first chamber. The chambers can contain a low acoustic impedance medium. As a result, the ultrasound energy produced from the second end and the external surface of the catheter is delivered at an increased efficiency. Such a catheter efficiently delivers ultrasound energy both distally and from the side of the catheter.
A catheter according to the present invention can also include a plurality of ultrasound transducers. Each ultrasound transducer can be associated with one or more chambers. As a result, each ultrasound transducer can have an increased efficiency.
An embodiment of a catheter having a plurality of ultrasound transducers includes ultrasound transducers with matched resonant frequencies. For instance, the catheter can include ultrasound transducers selected such that any one has a resonant frequency within about 1% of the resonant frequency of any other ultrasound transducer in the plurality of ultrasound transducers. The matching of the ultrasound transducers allows the ultrasound transducers to be concurrently driven at a single frequency while reducing the inefficiencies associated with driving ultrasound transducers at a frequency which is significantly different than their resonant frequency.
Another embodiment of the catheter includes a first binding medium adjacent to the first end of the ultrasound transducer and a second binding medium adjacent to the external side of the ultrasound transducer. The first and second media are selected to provide the catheter with flexibility and a high level of ultrasound transmission efficiency. Since a softer media is typically more flexible and harder media typically transit ultrasound energy more efficiently, the second medium is preferably harder than the first medium. The advantages of the first and second media are emphasized in multiple ultrasound transducer catheters which tend to lose flexibility with the increased number of ultrasound transducers.
Catheters according to the present invention can also include an autotransformer in the proximal portion of the catheter. The autotransformer can serve to adjust the characteristic impedance of the catheter to match the impedance of components used to drive the one or more ultrasound transducers included on the catheter. The matched impedance serves to increase the efficiency of the catheter system.
Catheters according to the present invention can also include a catheter identification electronics. The catheter identification electronics indicate to a catheter control system the frequency that ultrasound transducers should be driven.
The ultrasound assembly 10 includes an elongated body 12 with an external surface 14. A plurality of spacers 16 are positioned over the external surface 14 of an elongated body 12 and a member 18 is positioned over at least a portion of the spacers 16. The ultrasound assembly 10 also includes an ultrasound transducer 20 with an external side 22 and an internal side 24 between a first end 26 and a second end 28. The ultrasound transducer 20 is positioned over the member 18 and can surround the member 18. Suitable materials for the member 18 include, but are not limited to, polyimide, polyester and nylon. A suitable ultrasound transducer 20 includes, but is not limited to, PZT-4D, PZT-4, PZT-8 and various piezoceramics.
The internal side 24 of the ultrasound transducer 20, the spacers 16 and the member 18 each define a portion of a chamber 30 between the internal side 24 of the ultrasound transducer 20 and the external surface 14 of the elongated body 12. The chamber 30 preferably has a height from 0.25–10 μm, more preferably from 0.50–5 μm and most preferably from 0.0–1.5 μm.
The member 18 can extend beyond the first end 26 and/or the second end 28 of the ultrasound transducer 20. Additionally, the spacers 16 can be positioned beyond the ends of the ultrasound transducer 20. As a result, the chamber 30 can extend along the longitudinal length of the ultrasound transducer 20 to increase the portion of the ultrasound transducer 20 which is adjacent to the chamber 30.
The chamber 30 can contain a low acoustic impedance medium. Suitable low acoustic impedance media include, but are not limited to, fluids such as helium, argon, air and nitrogen and/or solids such as silicone and rubber. The chamber 30 can also be evacuated. Suitable pressures for an evacuated chamber 30 include, but are not limited to, negative pressures to −760 mm Hg.
As illustrated in
A transducer sheath 34 is positioned over at least a portion of the ultrasound transducer 20 and the collar 32 to form a chamber 30 adjacent to a side of the ultrasound transducer 20. An inner side of the collar 32, the ultrasound transducer 20 and the transducer sheath 34 each partially define the chamber 30. The chamber 30 preferably has a width, W, from 12–2500 μm, more preferably from 25–250 μm and most preferably from 25–125 μm. The chamber 30 can contain a low acoustic impedance medium. Suitable materials for the transducer sheath 34 include, but are not limited to air, N2, O2, and vacuum. The transducer sheath 34 preferably has a thickness from 10–100 μm and more preferably from 25–50 μm.
The ultrasound assembly 10 can also include a chamber 30 adjacent to the second end 28 of the ultrasound transducer 20 as illustrated in
Each of the chambers can be isolated from one another. However, when the ultrasound assembly 10 includes a chamber 30 between the ultrasound transducer 20 and the elongated body 12, one or more of the spacers 16 can be formed of a porous material to provide communication between the chambers 30. This communication can permit the pressures in each of the chambers 30 to reach an equilibrium. Alternatively, one or more of the spacers 16 can include channels, lumens 38 and/or a ridged external surface to permit the communication between chambers 30.
An embodiment of the ultrasound assembly 10 does not include a chamber 30 between the elongated body 12 and the internal side 24 of the ultrasound transducer 20 as illustrated in
The ultrasound assembly 10 of
A utility lumen 38 extends through the elongated body 12. The utility lumen 38 can be sized to receive a guidewire, to deliver therapeutic media including drugs, medication, microbubbles and other compounds which provide a therapeutic effect. Although, the elongated body 12 is illustrated as having a single utility lumen 38, the elongated body 12 can include a plurality of lumens 38 or can be solid.
Each of the ultrasound assemblies 10 illustrated in
Each ultrasound assembly 10 discussed and/or suggested above can include an assembly 10 sheath.
A volume between the assembly sheath 44 and the ultrasound transducer 20 can contain a binding medium 42 as illustrated in
Each of the ultrasound assemblies 10 illustrated above show the elongated body 12 extending outward from the ultrasound assembly 10. However, the elongated body 12 can be trimmed to provide an elongated body 12 which is flush with one or more sides of the elongated body 12. Additionally, a sensor such as a temperature sensor can be positioned in the binding medium 42 associated with any of the above ultrasound assemblies 10.
The collar 32 can be integral with the spacers 16 as illustrated in
The catheter includes a catheter body 52 having an external surface 53, a distal portion 54 and a proximal portion 56. The catheter body 52 can include an extension region 58, an assembly region 60 and a terminal region 62. Lumens 38 within the extension region 58, assembly region 60 and terminal region 62 are aligned with one another to provide one or more lumens 38 extending through the entire catheter. These lumens 38 can be sized to receive a guidewire or for the delivery of a therapeutic agent such as a drug.
The extension region 58 includes an extension body 64 having one or more lumens 38. The one or more lumens 38 included in the extension body 64 have cross sectional dimensions approximating the cross section dimensions of the one or more utility lumens 38 of the elongated body 12. The extension body 64 can be used to add length to the catheter.
Specifically, the extension body 64 can provide additional length beyond the length provided by the assembly region 60. Accordingly, the extension body 64 can be short or can be eliminated from the catheter body 52. Suitable materials for the extension body 64 include, but are not limited to, polyimide, silicone, and polyurethane.
The terminal region 62 is positioned at the distal tip of the catheter. The terminal region 62 includes a terminal body 66. The terminal body 66 can be solid or include one or more lumens 38 with cross sectional dimensions approximating the cross section dimensions of the one or more utility lumens 38 of the elongated body 12. Suitable materials for the terminal region 62 include, but are not limited to, polyimide, silicone, and polyurethane. The assembly region 60 is the region of the catheter body 52 including any of the ultrasound assemblies 10 discussed and/or suggested above.
A catheter sheath 68 is positioned over the extension region 58, the assembly region 60 and the terminal region 62 so as to define a portion of the external surface 53 of the catheter body 52. The catheter sheath 68 can serve to immobilize the extension region 58, the assembly region 60 and the terminal region 62 relative to one another. The catheter sheath 68 is optional and can be removed from the catheter body 52.
The volume between the ultrasound assembly 10 and the extension body 64 can contain a binding medium 42. Such binding media can serve to couple the extension region 58, the assembly region 60 and the terminal region 62 together. Suitable materials for the catheter sheath 68 include, but are not limited to polyethelyne, polyurethane, and polyimide. The thickness of the catheter sheath 68 material is preferably 0.001″ to 0.020″, more preferably 0.004″ to 0.010″ and most preferably 0.006″ to 0.008″.
As illustrated in
The first binding medium 42A can also be positioned adjacent to the external side 22 of the ultrasound transducer 20 as illustrated in
As illustrated in
The first binding medium 42A and the second binding medium 42B can be the same or different. When the second binding medium 42B is different than the first binding medium 42A, the second binding medium 42B is preferably harder than the first binding medium 42A. A harder binding medium 42 typically transmits ultrasound energy more efficiently than a softer binding medium 42. As a result, the hardness of the second binding medium 42B can preserve the ultrasound transmitting efficiency of the catheter. Additionally, the softness of the first binding medium 42A provides the catheter with additional flexibility. As a result, the choices of the first and second binding media effect both the flexibility and the ultrasound transmission efficiency of the catheter.
The second binding medium 42B is preferably at least 2 times harder than the first binding medium 42A and more preferably from about 3 to about 5 times harder than the first binding medium 42A. The first binding medium 42A preferably has a hardness of at least about 10 Shore D, more preferably from about 15 to about 80 Shore D and most preferably from about 20 to about 40 Shore D. The second binding medium 42B preferably has a hardness of at least about 60 Shore D, more preferably from about 65 to about 120 Shore D and most preferably from about 80 to about 100 Shore D.
As described above, any of the ultrasound assemblies 10 described and/or suggested above can be included in a catheter according to the present invention.
The catheter of
Two or more of the first, second and third binding media can be the same or they can all be different. In a preferred embodiment, the first and second binding media are the same while the third binding medium 42C transmits is harder than the first and second binding media. Accordingly, when the first and second binding media are the same, the third binding media is preferably harder than the first binding medium 42A. Preferably, the first binding medium 42A is also more flexible than the third binding medium 42C. Further, the third binding medium 42C is preferably at least 2 times harder than the first binding medium 42A and more preferably from about 3 to about 5 times harder than the first binding medium 42A. Additionally, the first binding medium 42C preferably has a hardness of at least about 10 Shore D, more preferably from about 15 to about 80 Shore D and most preferably from about 20 to about 40 Shore D. The third binding medium 42B preferably has a hardness of at least about 60 Shore D, more preferably from about 65 to about 120 Shore D and most preferably from about 80 to about 100 Shore D. In another preferred embodiment, the second and third binding media are each harder than the first binding medium 42A. In another preferred embodiment, the second and third binding media are the same and are harder than the first binding medium 42A.
Two or more of the first, second and third binding media can be the same or they can all be different. The second binding medium 42B preferably transmits ultrasound energy more efficiently than the first binding medium 42A. Further, the first binding medium 42A is preferably more flexible than the second binding medium 42B. The first and second binding media preferably have the hardness relationships and levels described with respect to the first and second binding media of
The catheter can include two or more ultrasound assemblies 10 as illustrated in
Two or more ultrasound assemblies 10 can share a member 18 as illustrated in
As illustrated in
As illustrated in
In
In
The methods described in
As illustrated in
As illustrated in
When the quantity of binding medium 42 precursor delivered fills the volume adjacent to the external side 22 of the ultrasound transducer 20, a second binding medium 42B precursor can be delivered into the volumes adjacent to the ends of the ultrasound transducer 20 as illustrated in
Once the binding media delivered above have solidified, the catheter sheath 68 can be removed from the catheter body 52. Additionally, once a chamber 30 is formed, a fluid low acoustic impedance medium can be delivered into the chamber 30. A low acoustic impedance medium preferably has an acoustic impedance less than about 1.7 Megarayls, more preferably of about 0–0.7 Megarayls and most preferably from 0–0.4 Megarayls. As described above, suitable low acoustic impedance media include, but are not limited to, helium, argon, air and nitrogen. These media can be delivered into the chamber 30 during or after the media solidification process using an injection device such as a hypodermic needle 70. Similar techniques can be used to draw a vacuum within the chamber 30. Solid low acoustic impedance media such as silicones and rubbers can be positioned within the chamber 30 during the formation of the ultrasound assembly 10.
The methods for forming a catheter described with respect to
When the ultrasound assembly 10 or catheter includes multiple ultrasound transducers 20, the methods for forming the ultrasound assembly 10 or catheter can include matching the resonant frequencies of the ultrasound transducers 20. For instance, the ultrasound transducers 20 can be selected such that any member of the plurality of ultrasound transducers 20 has a resonant frequency within about 10% of the resonant frequency of any other ultrasound transducer 20. More preferably, the ultrasound transducers 20 are selected such that any one has a resonant frequency within about 3%, even more preferably within about 1% and most preferably within about 0.5% of any other ultrasound transducer 20 in the plurality of ultrasound transducers 20. The selected ultrasound transducers 20 are then used to form an ultrasound assembly 10 or catheter.
The matching of the ultrasound transducers 20 allows the ultrasound transducers to be concurrently driven at a single frequency while reducing the inefficiencies associated with driving ultrasound transducers 20 at a frequency which is significantly different than their resonant frequency. Since the ultrasound transducers 20 can be driven at a single frequency, the matching the resonant frequencies of the ultrasound transducers 20 is preferred when the plurality of ultrasound transducers 20 are connected in parallel or in series.
The electrical connections for driving the one or more ultrasound transducers 20 can be done at various stages during the assembly of the catheter and/or ultrasound assembly 10. For instance, electrical wires can be coupled with the ultrasound transducers 20 before the ultrasound transducers 20 are positioned over the elongated body. Additionally, the electrical wires can be coupled with the ultrasound transducers 20 after the ultrasound transducers 20 are in position over the elongated body. Further, electrical connections can be made alternating with positioning the ultrasound transducers 20 over the elongated body.
Alternatively, one or more electrical wires can be positioned along the elongated body before the ultrasound transducers 20 are positioned over the elongated body. One or more ultrasound transducers 20 can then be slid over the elongated body such that the one or more electrical wires contact the inner side of the ultrasound transducers 20. The contact between the ultrasound transducers 20 and the electrical wire can serve as the electrical connection to the one or more ultrasound transducers 20. When a catheter or ultrasound assembly 10 includes more than one ultrasound transducer 20, the ultrasound transducers 20 can be connected in parallel, in series or independently connected. Wires extending from the one or more ultrasound transducers 20 can be threaded up through one or more lumens 38 in the extension body 64.
During the formation of the catheter and/or formation of the ultrasound assemblies 10, one or more sensors can be included in any of the media described above. The sensor can be positioned within a volume before a medium is delivered into the volume. Alternatively, the sensor can be delivered into a binding medium 42 precursor while the binding medium 42 precursor is in a flowable state. Wires extending from the one or more sensors can be threaded up through one or more lumens 38 in the extension body 64. Suitable sensors for use with the catheter include, but are not limited to, a temperature sensor. When a catheter includes one or more temperature sensors, the temperature sensor is preferably positioned adjacent to the external side 22 of an ultrasound transducer 20. Specifically, the one or more temperature sensors are preferably positioned in a volume between the external side 22 of the ultrasound transducer 20 and the external surface 53 of the catheter body 52.
The solidification of the binding medium 42 precursors can occur concurrently or independently of one another. As discussed with respect to
Binding medium 42 precursors for use with the catheters and ultrasound assemblies 10 discussed above are preferably flowable to optimize delivery into a desired volume. These precursors preferably solidify to a binding medium 42 having a reduced flowability. These precursors more preferably solidify to a binding medium 42 having a reduced flowability and an increased degree of adhesiveness. This solidification can occur through mechanisms including, but not limited to, cooling, setting and curing. Suitable binding media precursors and/or binding media include, but are not limited to, adhesives, epoxies, polymers, plastics, rubbers. Examples of suitable binding media with different degrees of hardness are EPOTEK 310 having a hardness of about 22 Shore D and HYSOL 3561 and 2939 having a hardness of about 85 Shore D. The binding media to be used can be selected for its particular hardness. Alternatively, binding media, such as epoxies, cure to a different hardness based on the component ratio in the binding media. The component ratio can be adjusted to achieve the desired hardness.
The binding media adjacent to the external side 22 of the ultrasound transducer 20 and/or adjacent to the ends of the ultrasound transducer 20 preferably has an acoustic impedance of about 1–20 Megarayls, more preferably about 1.3–10 Megarayls and most preferably about 4–8 Megarayls. As described above, the low acoustic impedance medium contained within the chambers preferably has an acoustic impedance less than about 1.7 Megarayls, more preferably of about 0–0.7 Megarayls and most preferably from 0–0.4 Megarayls. Further, the ratio of the acoustic impedances for the binding medium adjacent to the external side and/or adjacent ends the of the ultrasound transducer 20 measured relative to the acoustic impedance of the low acoustic impedance medium contained within the chambers is preferably at least 1.5:1, more preferably at least 2:1 and most preferably at least 4:1. Additionally the ratio is preferably 1.5:1 to 10,000:1, more preferably about 1.5:1 to 100:1 and most preferably 1.5:1 to 4:1.
The electrical coupling 74 includes an autotransformer 76 for adjusting the characteristic impedance of the catheter to match the impedance of an amplifier included in the catheter control system. For instance, if the amplifier has an input impedance of 50 ohms and the catheter has a characteristic impedance of 40 ohms, the addition of the autotransformer can provide the catheter with a characteristic impedance of about 50 ohms. The matched impedance serves to increase the efficiency of the catheter system.
Because each catheter can have a different characteristic impedance, the windings on the autotransformer can be adjusted to match the particular catheter of interest. As a result, a method of assembling a catheter can include the step of providing an autotransformer which matches the characteristic impedance of the catheter to the characteristic impedance of a component in a catheter control system.
The electrical coupling also includes catheter identification electronics 78. The catheter identification electronics 78 indicate to the catheter control system what frequency the catheter should be driven. For instance, the catheter identification electronics 78 can be one or more resistors. The catheter control system can include logic for identifying the resistance. This resistance can be associated with a catheter of a particular frequency. The logic can identify the particular frequency of the catheter and can then cause the catheter to be driven at the indicated frequency. A computer chip is another example of suitable catheter identification electronics 78. The computer chip can produce signals indicating the frequency of the catheter to the catheter control system. In response, the catheter control system can drive the catheter at the appropriate frequency.
A catheter according to the present invention can be used by itself or can be used in conjunction with a sheath 82 as illustrated in
The catheter can be rotated or moved within the sheath 82 as illustrated by the arrow labeled A. The movement of the catheter within the sheath 82 can be caused by manipulating the proximal portion of the catheter body 52 while holding the sheath proximal end 84 stationary. Although not illustrated, the sheath distal end 86 can include on or more temperature sensors.
As illustrated in
The drug delivery ports 94 are positioned close enough to achieve a substantially even flow of drug solution around the circumference of the sheath 82. The proximity of adjacent drug delivery ports 94 can be changed by changing the density of drug delivery ports 94 along the drug delivery lumen 92 or by changing the number of windings of the drug delivery lumen 92 around the energy delivery section 90. Suitable displacement between adjacent drug delivery ports 94 includes, but is not limited to, from 0.1″ to 1.0″, preferable 0.2″ to 0.6″.
The size of the drug delivery ports 94 can be the same or change along the length of the drug delivery lumen 92. For instance, the size of the drug delivery ports 94 distally positioned on the drug delivery section can be larger than the size of the drug delivery ports 94 which are proximally positioned on the drug delivery section. The increase in sizes of the drug delivery ports 94 can be designed to produce similar flowrates of drug solution through each drug delivery port 94. This similar flowrate increases the uniformity of drug solution flowrate along the length of the sheath 82. When the drug delivery ports 94 have similar sizes along the length of the drug delivery lumen 92, a suitable size for a drug delivery port includes, but is not limited to 0.0005″ to 0.0050″. When the size of the drug delivery ports 94 changes along the length of the drug delivery lumen 92, suitable sizes for proximally positioned drug delivery ports 94 includes, but is not limited to from 0.0001″ to 0.005″ and suitable sizes for distally positioned drug delivery ports 94 includes, but is not limited to, 0.0005″ to 0.0020″. The increase in size between adjacent drug delivery ports 94 can be substantially uniform between or along the drug delivery lumen 92. The dimensional increase of the drug delivery ports 94 is dependent upon material and diameter of the drug delivery lumen 92. The drug delivery ports 94 can be formed by burnt into the sheath 82 with a laser.
Uniformity of the drug solution flow along the length of the sheath 82 can also be increased by increasing the density of the drug delivery ports 94 toward the distal end of the drug delivery lumen 92.
The drug delivery ports 94 can optionally be closed slits in the sheath 82. The slits can have a straight or arcuate shape. When the dug delivery lumen 92 contains drug solution, the slits remain closed until the pressure within the drug delivery lumen 92 exceeds a threshold pressure. As the pressure within the drug delivery lumen 92 builds, the pressure on each of the slits will be approximately uniform. Once, the threshold pressure is reached, the uniform pressure will result in the slits opening almost simultaneously and cause a nearly uniform flow of drug solution out of all the slits. When the pressure within the drug delivery lumen 92 falls below the threshold pressure, the slits close and prevent delivery of additional drug solution. The stiffer the material used to construct the drug deliver lumen 38, the higher the threshold pressure required to open the slit shaped drug delivery ports 94. The slit shape can also prevent the drug delivery ports 94 from opening when exposed to low pressures from outside the sheath 82. As a result, slit shaped drug delivery ports 94 can maximize control of drug delivery.
In
In
In
While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than limiting sense, as it is contemplated that modifications and combinations will readily occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the appended claims.
This application is a Continuation Application of U.S. patent application Ser. No. 09/375,162, filed on 16 Aug. 1999, now U.S. Pat. No. 6,582,392 which is incorporated by reference herein in its entirety. Co-pending U.S. patent application Ser. No. 09/375,162 a Continuation-In-Part of U.S. patent application Ser. No. 09/129,980, now U.S. Pat. No. 6,210,356, filed 5 Aug. 1998 and issued 3 Apr. 2001. Co-pending U.S. patent application Ser. No. 09/375,162 is also a Continuation-In-Part Application of U.S. patent application Ser. No. 09/107,078, filed 29 Jun. 1998 now U.S. Pat. No. 6,723,063. Co-pending U.S. patent application Ser. No. 09/375,162 is also a Continuation-In-Part of U.S. patent application Ser. No. 09/071,285 now U.S. Pat. No. 6,001,069, filed 1 May 1998 and issued 14 Dec. 1999. U.S. Pat. No. 6,001,069 claims priority to U.S. Provisional Patent Application 60/045,268, which was filed on 1 May 1997.
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