Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-02-09
2001-05-15
Dvorak, Linda C. M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C606S033000, C607S156000
Reexamination Certificate
active
06233490
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 and systems 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 includes an antenna for radiating energy from a source of electromagnetic energy and including a first radiating element and a second radiating element having a conductor helically wound and coaxially positioned around the first radiating element to receive energy radiated by the first radiating element. The first and second radiating elements are positioned substantially along a longitudinal axis of the antenna with the first radiating element having a proximal end coupled to the source of electromagnetic energy.
With this arrangement, energy from the electromagnetic source is efficiently conveyed from the first radiating element and then resonates the coaxially positioned and helically wound second radiating element. The transmission of energy is performed efficiently and in a relatively compact arrangement.
Embodiments of this aspect of the invention may include one or more of the following features.
The second radiating element is electrically floating relative to electrical ground and represents a helix “slow-wave” circuit, which receives energy from the first radiating element and then radiates the energy to the tissue. One or more impedance elements (e.g., capacitors) are electrically connected between preselected windings of the helically wound first radiating element. Connecting the impedance elements between the windings allows the use of a much shorter helical winding. Without impedance loading, a helical winding of much longer length would be required for resonance and efficient radiation at the desired frequency of operation.
At least one of the first and second radiating elements are moveable along the longitudinal axis of the antenna with respect to the other of the radiating elements. For example, the first radiating element is moveable with respect to a stationary second radiating element. A mechanism, such as a micrometer caliper, is provided to move the first radiating element to achieve a minimum reflection coefficient. Thus, a surgeon or therapist can adjust the position of the first radiating element relative to the second radiating element so that both elements radiate together with near-perfect impedance match, thereby maximizing power transfer efficiency to the surrounding tissue.
An impedance matching network is coupled between the first radiating element and the electromagnetic source to maximize power transfer therebetween. In preferred embodiments, the impedance matching network is spaced approximately one-quarter wavelength from the first radiating element at the operation frequency of the electromagnetic source.
The first radiating element may be in the form of a dipole antenna. For example, the first radiating element includes a center conductor, an outer conductor, and a dielectric member positioned between the center conductor and outer conductor. Alternatively, the first radiating element is in the form of a helically wound conductor having a second diameter less than a first diameter of the helically wound second radiating element. The first radiating element can be wound about a ferrite member.
The medical treatment system includes a device for measuring an input impedance characteristic (e.g., reflection coefficient) of the first radiating element. In embodiments in which the first radiating element is a coaxial line having an outer conductor spaced from an inner center conductor by a dielectric, the impedance matching network includes a conductive shield surrounding the outer conductor and has a first end electrically connected to the outer conductor.
The electromagnetic energy 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 a related aspect of the invention, a medical heat treatment system includes a pair of medical instruments, each including an antenna system disposed within a catheter, with at least a first one of the antenna systems being a transmitting antenna system and including a first radiating element and a second radiating element including a conductor helically wound and coaxially positioned around the first radiating element. The catheters are of the type having a proximal end, distal end, and a longitudinal axis extending therebetween. The treatment system also includes an electromagnetic energy source electrically coupled to said collinear array to provide the electromagnetic energy to the first radiating element.
In embodiments of this aspect of the invention, a second one of the pair of medical instruments includes a receiving antenna system for receiving signals from the transmitting antenna system. The signals are representative of the material properties of the media positioned between the receiving antenna system and the transmitting antenna system (e.g., impedance of the media or attenuation and phase constants of the media). In this embodiment, the medical treatment system further includes a network analyzer connected to the receiving antenna system, which receives the signals from the transmitting antenna system.
In a related aspect of the invention, a method of treating the prostate with the medical treatment system having a pair of medical instruments described above includes the following steps. A first one of the pair of medical instrument is positioned within the urethra, while a second one of the pair of medical instrument is positioned within the rectum. Electromagnetic energy is applied to the first of the pair of medical instruments to radiate the prostate.
In particular embodiments using this approach, the second one of the pair of medical instruments receives the electromagnetic energy passing through the prostate. Alternatively, both the first and second medical instruments are used to radiate the prostate.
Other features and advantages of the invention will be apparent from the drawings, the following Detailed Description, and the claims.
REFERENCES:
patent: 3919638 (1975-11-01), Belden, Jr.
patent: 4204549 (1980-05-01), Paglione
patent: 4527550 (1985-07-01), Ruggera et al.
patent: 4700716 (1987-10-
Dvorak Linda C. M.
Fish & Richardson P.C.
KAI Technologies, Inc.
Ruddy David M.
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