Method for manufacturing small diameter medical devices

Details Method for manufacturing small diameter medical devices Method for manufacturing small diameter medical devices

2002-03-06

2003-11-18

Crane, Daniel C. (Department: 3725)

Metal deforming

By pulling workpiece through closed periphery die

Utilizing specified work moving means

C072S276000, C072S285000, C072S286000

Reexamination Certificate

active

06647755

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the manufacture of small diameter medical devices. More particularly, the present invention is an apparatus and method for manufacturing small diameter ultrasonic probes capable of vibrating in a transverse mode that can be used in ultrasonic medical devices for tissue ablation.
BACKGROUND OF THE INVENTION
Ultrasonic probes are devices which use ultrasonic energy to fragment body tissue or debris (see, e.g., U.S. Pat. No. 5,112,300; U.S. Pat. No. 5,180,363; U.S. Pat. No. 4,989,583; U.S. Pat. No. 4,931,047; U.S. Pat. No. 4,922,902; and U.S. Pat. No. 3,805,787) and have been used in many surgical procedures. The ultrasonic energy produced by an ultrasonic probe is in the form of very intense, high frequency sound vibrations that result in powerful chemical and physical reactions in the water molecules within a body tissue or surrounding fluids in proximity to the probe. These reactions ultimately result in a process called “cavitation,” which can be thought of as a form of cold (i.e., non-thermal) boiling of the water in the body tissue, such that microscopic bubbles are rapidly created and destroyed in the water creating cavities in their wake. As surrounding water molecules rush in to fill the cavity created by collapsed bubbles, they collide with each other with great force. Cavitation results in shock waves running outward from the collapsed bubbles which can wear away or destroy material such as surrounding tissue or debris in the vicinity of the ultrasonic probe. Medical applications for ultrasonic probes include, for example, treatment of cancer, tissue remodeling, liposuction, tissue biopsy, and removal of vascular occlusions.
A drawback of existing ultrasonic medical probes is that they typically remove tissue slowly in comparison to instruments that excise tissue by mechanical cutting, electrocautery, or cryoexcision methods. Part of the reason for the slow removal of tissue is that most existing ultrasonic devices rely on a longitudinal vibration of the tip of the probe for their tissue-disrupting effects. Because the tip of the probe is vibrated in a direction in line with the longitudinal axis of the probe, a tissue-destroying effect is only generated at the tip of the probe. The concentration of energy at the probe tip results in the generation of heat at the probe tip, which can create tissue necrosis, thereby complicating the surgical procedure and potentially compromising the recovery of the patient.
Complications such as these may be avoided by an ultrasonic device which includes an ultrasonic probe whose vibrations are restricted to occur exclusively in a transverse direction to the probe axis (perpendicular). By eliminating the axial motion of the probe and allowing transverse vibrations only, fragmentation of large areas of tissue spanning the entire length of the probe is possible due to generation of multiple cavitational nodes along the probe length perpendicular to the probe axis. Since substantially larger affected areas within an occluded blood vessel, organ, graft or port can be denuded of the occluding tissue or debris in a short time, actual treatment time using the transverse mode ultrasonic medical device is greatly reduced as compared to methods using probes that primarily utilize longitudinal vibration (along probe axis) for tissue or debris ablation. Another advantage to ultrasonic devices which operate in a transverse mode is their ability to rapidly remove tissue or debris from large areas within cylindrical or tubular surfaces which is not possible by devices that rely on the longitudinal vibrating probe tip for effecting tissue fragmentation.
Ultrasonic probes currently known in the art are generally made by a process of machining to achieve a diameter of approximately 0.020 inches, or greater, at the functional end of the probe. Dies are commonly known in the art and are used in the machining process (see, e.g., U.S. Pat. No. 5,840,151; U.S. Pat. No. 5,325,698; U.S. Pat. No. 5,261,805; and U.S. Pat. No. 6,062,059). Although it is possible to induce transverse vibrations at an ultrasonic probe diameter of 0.020 inches (see, e.g., U.S. Pat. No. 5,803,083; U.S. Pat. No. 5,058,570; U.S. Pat. No. 5,469,853; and U.S. Pat. No. 5,421,338), probe diameters less than 0.020 inches are crucial for the generation of sufficient cavitational energy via transverse vibration needed for the treatment of tissue. Since probes vibrating exclusively in a transverse mode must rely almost entirely on generation of sufficient cavitational energy to cause tissue ablation, the diameter of the distal segment of the probe and the probe tip have to be smaller than conventional prior art probes that are only capable of longitudinal vibration. The manufacturing methods for conventional, longitudinally vibrating ultrasonic probes disclosed in the art typically involve machining techniques to obtain probe diameters typically greater than 0.020 inches. Further reduction in probe diameter by such prior art methods is not attainable since the material making up the probe is highly susceptible to fracture.
Prior art attempts to manufacture ultrasonic probes having a small diameter have been less than successful. U.S. Pat. No. 5,527,273 to Manna et al. discloses a method of machining to achieve a diameter of 0.020 inches, or greater, at the distal end of the device. The Manna et al. process results in a probe having limited flexibility and the probe is not capable of producing significant cavitational energy via transverse vibrations. In addition, Manna et al. discloses manufacturing a small diameter device comprising providing a first section, a second section of different diameter, and a means to connect the first section to the second section. Although the small diameter of the distal end of the Manna et al. device allows for generation of cavitational energy, connecting a first section to a second section presents a high likelihood of fracture and an inefficient method of manufacturing the device. Thus, a need exists in the art for an ultrasonic probe having varying diameters that can be manufactured from a single metal stock.
U.S. Pat. No. 5,993,408 to Zaleski discloses a small diameter needle for cutting tissue at a distal end of the device. The Zaleski device, a thin tip phaco needle, comprises a body having a longitudinal bore for enabling passage of cut tissue therethrough. A distal end of the Zaleski device comprises a tip for cutting tissue and a proximal end for engaging a handpiece. The tip includes chamfer means for enhancing cutting efficiency of the tip. The chamfer means may be comprised of a beveled or stepped cutting edge of the tip, having a wide proximal wall and a thin distal wall, the distal wall having a cross section of about half of a cross section of the wide proximal wall. The Zaleski device is limited in that only tissue in contact with the tip of the needle is treated. Additionally, the Zaleski device is not used to create cavitational energy via transverse vibration along the length of the needle and there is no indication that the Zaleski device could be used to provide such energy. Further, the Zaleski patent does not disclose an apparatus or method of manufacturing the needle. Thus, a need exists in the art for an efficient and reliable method to manufacture small diameter ultrasonic probe.
U.S. Pat. No. 4,870,953 to DonMicheal et al. discloses an elongated, solid, flexible probe attached at one end to an ultrasonic energy source and having a rounded probe tip at a distal end, the probe tip being capable of both longitudinal and transverse motion. The DonMicheal et al. device is limited in that it does not disclose the treatment of tissue along a length of the probe and only discloses tissue treatment at the probe tip. Further, the DonMicheal et al. patent does not disclose an apparatus or method of manufacturing a small diameter medical device. Thus, a need exists in the art for an efficient and reliable method to manufacture small diameter ultrasonic probe.
Accordingly, there

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