Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-02-09
2001-01-30
Dvorak, Linda C. M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S102000, C607S156000
Reexamination Certificate
active
06181970
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to microwave devices used in medical hyperthermia and thermotherapy (referred to collectively herein as “heat therapies”), and diagnostics, and to methods of using such devices.
Localized heat therapies, i.e., hyperthermia (heating to temperatures below 45° C.) and thermotherapy (heating to temperatures above 45° C.), have been intensively investigated for the last two decades for many disease processes including benign prostatic hyperplasia (BPH) and neoplasms.
However, methods of delivering heat including warm fluid, focused ultrasound, radio frequency, and microwave approaches have been applied to abnormal tissue with only limited success. The prostate gland is one organ targeted as a candidate for applying heat delivery techniques. Because microwave energy can be applied without incision, this approach is one being evaluated. Furthermore, this technique advantageously can be applied in an outpatient setting.
For heat therapy to be applied safely, it is very important that the applied heat be confined to the target area (e.g., BPH tumor) alone, to avoid damaging nearby healthy tissue or organs.
Some devices for heat therapy have utilized microwave heating, for example those disclosed in U.S. Pat. Nos. 4,700,716 and 4,776,086, the disclosures of which are incorporated herein by reference. Microwave energy elevates temperature by increasing the molecular motion within cell structures. As the frequency decreases, tissue penetration increases. Small diameter microwave antenna probes have been inserted into the body through normal body passages or, on occasion, directly into diseased tissue, using hollow plastic catheters.
SUMMARY OF THE INVENTION
The invention features medical instruments which utilize microwave energy to provide heat treatment and diagnostic imaging of tissue. The term “microwave”, as used herein, refers to electromagnetic energy in the microwave frequency spectrum of 300 Mhz to 300 GHz.
In one aspect of the invention, a medical treatment system for treating tissue including an antenna having a radiating element configured to transmit electromagnetic energy toward a desired area of the tissue and having an interior volume for receiving a heat exchange fluid, thereby changing the temperature proximal to the desired area of the tissue.
The invention has numerous advantages. A radiating element having this arrangement is multifunctional. In particular, the radiating element is used to transmit energy toward the tissue to heat or provide an image of the tissue. In addition, the radiating element serves as a “heat pipe”, which acts as a source or sink for thermal energy at the desired area, improving control of the temperature of the volume of tissue being radiated by the antenna. Thus, a safer, more efficacious delivery of microwave energy is provided. It is important to recognize that although the radiating element serves as a “heat pipe”, in operation, it can provide both heating as well as cooling, depending on whether the fluid (e.g., liquid or gas) is hot or cold.
In a related aspect of the invention, a medical heat treatment system includes a first medical instrument having an antenna system configured having a radiating element with the arrangement described in the previously discussed aspect and a second medical instrument having a second antenna system for receiving the radiated electromagnetic energy from the first medical instrument.
Embodiments of these aspects of the invention may include one or more of the following features.
The medical treatment system includes a transmission line connected to the radiating element for conveying the electromagnetic energy from an electromagnetic energy source to the radiating source. A conduit extends through the transmission line to convey the heat exchange fluid (e.g. coolant) from a heat exchanger (e.g., compressor) to the radiating element. In certain embodiments, the interior volume of the radiating element and conduit is sized to cause capillary action of fluid flowing therethrough.
In one embodiment, the transmission line is coaxial transmission line including a hollow center conductor and an outer shield disposed coaxially with respect to the center conductor. The coaxial transmission line includes a transformer which serves as an impedance matching network for maximizing power transfer between the electromagnetic energy source and antenna. The transformer is spaced from the radiating element a quarter wavelength at a predetermined frequency of operation and includes a metallic sleeve surrounding the outer shield of the coaxial transmission line. The antenna may have a wide variety of configurations including dipole arrangements. The medical treatment system further includes a catheter having an inner lumen extending between a proximal end and a distal end, and sized to receive the antenna.
The medical treatment system includes a plurality of antennas, each having a radiating element for transmitting electromagnetic energy toward the desired area. In certain embodiments, the antennas are formed as a collinear array of antennas. In this case, each of the antennas is configured to radiate electromagnetic energy at a selected amplitude and phase characteristic so that the transmitted energy, in aggregate, is directed toward a desired area of the tissue. One or more temperature detectors are provided for sensing the temperature at a location proximate to the radiating element. In response to the sensed temperature, the detectors provide signals to the heat exchanger to control the amount of fluid delivered to the interior volume of the radiating element. Each temperature detectors is preferably positioned to be associated with a different area of the radiating element.
The electromagnetic energy provided by the source has a frequency in a range between 0.3 and 10 GHz and a power level in a range between about 100 mwatts and 150 watts.
In another aspect of the invention, a method of treating tissue with the medical treatment system described above includes the following steps. The first medical instrument is positioned within a first body passage. The second medical instrument is positioned within a second body passage. Electromagnetic energy is then applied to the first medical instrument to heat a desired area of the tissue with the second medical instrument receiving the electromagnetic energy transmitted by the first medical instrument and passing through the tissue. Areas proximal to the tissue are cooled with the first medical instrument.
Other features and advantages of the invention will be apparent from the drawings, the following Detailed Description, and the claims.
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Dvorak Linda C. M.
Fish & Richardson P.C.
KAI Technologies, Inc.
Ram Jocelyn
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