Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-08-31
2002-08-13
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S333000
Reexamination Certificate
active
06433464
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for removing materials utilizing ultra-high frequency acoustical waves, especially as related to surgical procedures.
BACKGROUND OF THE INVENTION
It is known in the art to use relatively low ultrasonic frequency energy for a wide variety of purposes ranging from communications to polishing. Of particular interest in the art is removal of soft tissue from inaccessible locations.
U.S. Pat. No. 3,589,363 describes a vibratory assembly for removing material from relatively inaccessible regions. This instrument uses a rapidly vibrating knife tip to break down unwanted material into small particles. As the vibrating tip is applied to the material, the region adjacent to the operative site is flooded with fluid. The unwanted material is dispersed into the fluid which, in turn, is removed by suction. Although the vibrating tip will, as a result of this motion, produce an acoustical wave which propagates into the unwanted material, it is recognized in the art that the cutting motion of the tip, and not just the propagation of radiated acoustical energy, produces the desired action and result. (See, for example, C. D. Kelman, “A Personal Interview Between the Editor and Dr. Charles D. Kelmiani,”
Boyd's Highlights of Ophthalmology,
Volume XIII, No. 1, 1970-71 Series, p. 43.)
This type of technique, often referred to as phakoemulsification, is perhaps the most widely used “ultrasound” technique for removal of cataracts. Since the vibrating tip (or knife) used to cut away the material vibrates at a frequency of 30-40 kHz, it has been termed an “ultrasonic” method even though the device does not rely upon the propagation of an acoustical wave to cut away tissue. Although effective for what it does, the device is essentially a miniaturized electric knife. Some phako-devices operate at sufficient power levels or have sufficient tip excursions to generate cavitation bubbles. Such bubbles, when they implode, generate sufficient energy to break down material and can, in certain situations, create significant bioeffects.
Another so-called ultrasonic technique has recently been introduced by Baxter-Edwards Healthcare (see
Circulation,
89(4):1587-92 (1994)). Here the vibrating knife of phako has been replaced with a large ball tip. This device operates by “beating” the ball tip against the material to be removed. Material to be removed is broken up by the physical impact of the tool, or by shock waves and cavitation bubbles created by the vibrating tool.
Specifically with respect to methods for treating occluded arteries, balloon angioplasty is the most commonly used method today for recanalizing obstructed arteries. However, this method remains problematic in situations involving complete obstructions, multisegment and multivessel disease, or late restenosis. R. J. Siegel, M.D., describes a variety of techniques being investigated to resolve these problems, but states: “Each of these technologies also has limitations principally relating to endothelial damage and perforation.” (
Circulation,
78(6):1447 (1988)). In late restenosis, Siegel notes, “[a]ngioplasty carries an additional risk within the first six months. After the procedure is performed, about 35% of the blockages return although that can be relieved by a repeat angioplasty.” Id. When blockage re-occurs, secondary surgical intervention is generally necessary immediately.
Ultrasound has also been utilized to remove arterial obstructions. See, for example, Siegel et al.,
Lancet,
pp. 772-74 (Sep. 30, 1989), Ernst et al.,
Am. J. Cardiol.,
68:242-46 (1991), Siegel et al.,
Circulation,
89(4):1587-92 (1994), DonMicheal et al., U.S. Pat. No. 4,870,953. Guess et al., U.S. Pat. No. 5,069,664, Carter, U.S. Pat. No. 5.269,291, Marcus et al., U.S. Pat. No. 5,295,484, Hashimoto, U.S. Pat. No. 5,307,816, Carter. U.S. Pat. No. 5.362.309, Carter U.S. Pat. No. 5,431,663, and Rosenscihcini, U.S. Pat. No. 5,524,620. In fact, the highest frequency of acoustical waves disclosed in any of these references as suitable for removing arterial obstructions is 40 MHz (see the Marcus '484 patent), but, the highest frequency that is actually exemplified in Marcus '484 is only 14.4 MHz.
These references teach that ultrasound applied to ablate, or otherwise remove, plaque and thrombus operates by means of mechanical action, heat, or cavitation. Furthermore, these references teach that ultrasonic transducers produce a therapeutic effect at a significant distance from the transducer, 10 cm or more, by focusing the ultrasonic waves.
In addition to ultrasound, numerous groups disclose use of lasers to remove arterial plaque using a diversity of wavelengths (colors of light). Lasers in the infrared and visible wavelengths usually ablate by a thermal mechanism, although some may create shock waves or cavitation bubbles that break down tissue.
The excimer laser is successful in excimer laser keratectomy or “laser sculpting of the cornea” to correct vision. Since this laser operates in the ultraviolet region of the spectrum, it ablates tissue by high energy photons. Certain undesirable side effects that may be encountered in this method include ejection of particles at supersonic velocities, the generation of shock waves, and difficulty in distinguishing healthy from diseased tissue. Also, since the laser operates in the ultraviolet portion of the spectrum, the mutagenic effects of the laser itself and the secondary radiation emitted during the ablation pose possible complications that will not be fully assessed until a long term study is performed.
Another disease state wherein treatment requires destruction of tissue within an inaccessible body cavity is cancer of the prostate. An even greater problem, at least in terms of numbers, is benign prostatic hyperplasia (BPH) for which there are over 400,000 cases per year in the United States alone. For over sixty years, transurethral electroresection of the prostate (TURP) has been the surgical treatment of choice for symptomatic bladder outlet obstruction caused by BPH. For some time, TURP has been considered the “gold standard” for comparison when assessing other treatments for this disease.
Since TURP is not without morbidity or serious complications, the urology community has long sought alternate therapies. Currently, laser prostatectomy is proving to be a far better method for the treatment of BPH. In this method, a light fiber directs the energy of the laser (more often an Nd:YAG laser) into the prostate at a 90° angle with respect to the catheter where the unwanted material is burned. The destroyed tissue initially stays in place and eventually breaks down and is carried away by the urine over a period of six to twelve weeks. During this recovery period, the patient may experience considerable pain and will not regain normal function for some period of time.
Ultrasound treatment of prostate conditions, including prostate cancer and BPH, has been suggested in the art. See, for example, Watkin et al.,
Brit. J. Urol.,
75(supp. 1):1-8 (1995), Gelet et al.,
Eur. Urol.,
29:174-83 (1996), Schaetzle, U.S. Pat. No. 5,443,069, Chapelon et al., U.S. Pat. No. 5,474,071, Granz et al., U.S. Pat. No. 5,526,815, and Oppelt et al., U.S. Pat. No. 5,624,382. The highest frequency of acoustical waves disclosed in these articles is 9.8 MHz in the Watkin article. In the procedures described in this group of references, the ablation of tissue is accomplished through heating or cavitation caused by the ultrasound energy. When the ultrasonic waves are focused, such effects can occur at a significant distance from the transducer, for example, 10 cm or more.
The relatively low ultrasonic frequencies disclosed in the art travel much farther from the transducer through the tissue before being substantially attenuated than is desirable in many applications. In addition, during passage through tissue, the energy of low-frequency , ultrasound is converted to heat, physical forces, and acoustical pressures over all undesirably large area, as opposed to
Brooks Michael Blaine
Brooks & Fillbach
Dougherty Thomas M.
Learn June M.
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