Surgery – Means for introducing or removing material from body for... – With means for cutting – scarifying – or vibrating tissue
Reexamination Certificate
2001-07-02
2003-02-25
Kennedy, Sharon (Department: 3763)
Surgery
Means for introducing or removing material from body for...
With means for cutting, scarifying, or vibrating tissue
C600S466000
Reexamination Certificate
active
06524271
ABSTRACT:
TECHNICAL FIELD
The present invention relates to therapeutic ultrasound methods and catheter systems.
BACKGROUND OF THE INVENTION
Therapeutic ultrasound systems have proven effective in enhancing transdermal drug delivery, ablating pathological tissue and non-invasively breaking up concretions within the body. To achieve maximum therapeutic benefits, it is desirable to deliver ultrasound energy as directly as possible to the treatment site. Unfortunately, such treatment site may be within a body lumen, such as a vascular site, where numerous problems exist in attempting to direct therapeutic ultrasound. For example, it is difficult to design a sufficiently flexible device to deliver ultrasound energy along the curved tortuous path of the body lumen, especially for narrow diameter body lumens.
Moreover, to deliver maximum therapeutic benefits along a body lumen treatment region, it is desirable to direct a uniform dosage of ultrasonic energy along the length of the lumen with the dosage of the ultrasound energy varying only minimally along the length of the lumen. Delivering a uniform dose of therapeutic ultrasound energy along the length of the body lumen is especially desirable when concurrently using stents in the lumen. When using stents, overstretching of the vascular wall during stent insertion can cause wall tearing and denudation of endothelial cells which can result in an over proliferative healing response. Therapeutic ultrasound following wall injury reduces the formation of obstructive neointimal hyperplasia. A uniform dose of therapeutic ultrasound would reduce the formation of such hyperplasia along the length of the lumen, and in particular along the length of the stent.
It has proven especially difficult to generate such a uniform ultrasonic field along the length of a body lumen due in part to the typically curved path of the lumen and the dimensions of the ultrasound transducers.
Ultrasound systems which are effective in enhancing transdermal drug delivery operate at frequencies around 1 MHz, and tend to be quite large due to the large surface area that it is necessary to affect. Such large transducers are not suitably dimensioned for catheter placement into the small lumens of a patient's body. Moreover, smaller transducers which operate at higher frequencies, (such as 10 to 50 MHZ), are not adapted to generate sufficient energy to enhance in vivo drug delivery, or to cause other therapeutic effect, such as reducing the formation of obstructive neointimal hyperplasia after stent implantation. Instead, such small high frequency transducers are limited to diagnostic applications.
For catheter based systems, achieving the optimal size of the ultrasound transducer is problematic since a small catheter mounted transducer is only able to deliver a small amount of ultrasound energy to the patient. Conversely, a larger device, (which would deliver more therapeutic energy), requires a larger transducer which would unfortunately limit the flexibility of the catheter, thus making access difficult in narrow vascular regions.
In addition, a small catheter mounted transducer is adapted to deliver ultrasound only to the region of the lumen immediately adjacent the transducer, for example at the distal tip of the catheter. An additional problem when using a plurality of ultrasound transducers spaced apart along the length of the catheter is the non-uniformity of ultrasound dose delivered since maximum ultrasound will be delivered adjacent the transducers and minimal ultrasound will be delivered at locations equally spaced between adjacent transducers. Accordingly, it is especially difficult to deliver a uniform dose of ultrasound energy along the length of the body lumen.
U.S. Pat. No. 5,197,946 and published PCT Applications WO 96/27341 and WO 98/18391 to Tachibana disclose catheters having an ultrasound transducer at their distal end. Published PCT Application WO 98/48711 to Tachibana discloses a flexible catheter system directed to providing ultrasound for treating long lesions by providing a catheter having a number of separate ultrasound transducers spaced apart therealong. Published PCT Application WO 96/29935 to Crowley discloses a catheter system for tissue ablation having a plurality of annular shaped ultrasonic transducers spaced apart along the length of the catheter.
SUMMARY OF THE INVENTION
The present invention provides methods and systems for treating a target region in a body lumen by delivering a uniform dose of ultrasonic energy from an interior of the lumen radially outward along a portion of the length of the lumen. As will be explained herein, a “uniform” dosage of ultrasound energy corresponds to ultrasound energy producing a uniform biological effect around the circumference of the body lumen. Such uniform biological effects can be generated by mechanical effects related to cavitation, thermal bio-effects related to the absorption of ultrasound energy, radiation pressure forces arising from the absorption and reflection of ultrasound causing tension in the lumen to be equal around its circumference.
In a preferred aspect of the invention, the uniform dosage of ultrasonic energy received at any one point along the length of the lumen varies by no more ±6 decibels. Also in a preferred aspect of the invention, the uniform dosage of ultrasonic energy will be applied over a length greater than the diameter of the body lumen at the treatment site, usually being at least 0.8 cm of the lumen often being at least 1 cm, and sometimes being 2 cm, 3 cm, or longer.
In various aspects of the present invention, one or more ultrasound transducers are used to generate the uniform dose of ultrasound energy.
When using a single ultrasound transducer, the transducer may have an isotropic radiation pattern and be drawn axially through the lumen at a controlled velocity. Alternatively, when using a single non-isotropic ultrasound transducer, the transducer may be drawn axially through the lumen at a controlled velocity, while simultaneously being rotated about the central axis of the catheter at a controlled angular velocity.
When using a plurality of axially spaced apart isotropic transducers, the transducers may be drawn axially through the lumen at a controlled velocity. Alternatively, by dimensioning the axially spaced apart transducers such that they can be placed at a separation distance less than or equal to the diameter of the catheter, a generally uniform emission along the length of the body lumen can be generated without having to axially draw the transducers through the lumen.
When using a plurality of axially spaced apart non-isotropic transducers, the transducers may either be drawn axially through the lumen at a controlled velocity, rotated about the central axis of the catheter at a controlled angular velocity, or some combination thereof.
Preferred shapes for isotropic transducers include cylindrical or annular transducers having their central axes disposed parallel to the central axis of the catheter. A preferred shape for a non-isotropic transducer is a rectangular bar shaped transducer. Other non-isotropic shapes are also possible including cubic or octagonal shapes, parallel bar shapes or composite structures.
Preferred dimensions of the cylindrical, annular, rectangular or cubic transducers as set forth herein will cause the transducers to operate at resonance, thereby increasing the net therapeutic effect to the body lumen by providing maximum ultrasound energy.
When using a plurality of axially spaced apart transducers, the transducers can be operated in phase so as to cause tissue displacements in directions normal to a central axis of the lumen. Alternatively, the plurality of spaced apart transducers can be operated such that successive transducers are 180° out of phase with one another such that ultrasound energy causing tissue shear displacement along the length of the lumen is produced.
Specifically, when using a plurality of either rectangular bar shaped or cylindrical transducers, (with the transducers being positioned with their
Brisken Axel F.
Corl Paul D.
Cowan Mark W.
McKenzie John R.
Nassi Menahem
Kennedy Sharon
Pharmasonics, Inc.
Townsend and Townsend / and Crew LLP
LandOfFree
Therapeutic ultrasound catheter for delivering a uniform... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Therapeutic ultrasound catheter for delivering a uniform..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Therapeutic ultrasound catheter for delivering a uniform... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3136970