Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1999-12-06
2001-12-11
Gibson, Roy (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S096000, C607S154000, C607S156000
Reexamination Certificate
active
06330479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to applying microwaves to a material, and more particularly, to a flexible microwave array that can conform closely to complex curvatures of the human body for uniform heat treatment of superficially located tumors or benign skin conditions.
2. Description of the Prior Art
The use of microwave applicators for hyperthermia treatment of superficial tumors is well known. However, difficulties have been encountered in applying such devices to large areas with complex curvatures, such as in the neck and chest area, since the patients must, while retaining the antenna(s) of the microwave applicator in an evenly spaced perpendicular alignment with the surface of the skin, maintain proper inter-antenna spacing in order to facilitate uniform heat treatment. Generally, these microwave applicators are capable of heating areas of superficial tissue for treatment of skin and superficial tissue related diseases such as chestwall recurrence of breast carcinoma, psoriasis or other non-cancerous skin conditions that can benefit from tissue reoxygenation, or increased blood perfusion and blood vessel permeability.
Hyperthermia, which consists of heating tumors at a temperature of 42-45∞ C for about one hour, has been shown capable of enhancing the affects of common anti-cancer treatments such as radiotherapy and chemotherapy. Effective heat treatment for superficial disease requires an applicator capable of treating irregularly shaped and often widespread disease extending from the skin surface to a maximum depth of about 1 cm. While previously used microwave applicators operating at either 915 or 433 MHz have demonstrated appropriate penetration of Specific Absorption Rate (SAR) for generating effective heating down to a maximum depth of 1-1.5 cm, treatment of the entire lateral extent of disease is usually impossible due to limited applicator size and poor coupling of the rigid planar structures of previous microwave applicators to the skin surface. Because superficial tissue disease often wraps around complex body contours, the applicator must be thin and flexible for complete, closely conforming coverage of various-sized areas as well as lightweight for patient comfort during long treatments.
Thus, previous microwave applicators generally have been inadequate for treating many types of superficial tumors, such as chestwall recurrence of breast carcinoma, skin cancer, psoriasis, and other skin conditions, due to their large, bulky size as well as their generally inflexible, planar arrangement.
SUMMARY OF THE INVENTION
The present invention addresses the shortcomings of the prior art. A novel microwave applicator in accordance with the present invention is ideally suited for applying microwaves to skin and superficial tissue and thus is capable of uniformly heating large areas of superficial tissue over contoured anatomy for treatment of skin and superficial tissue related disease, such as chestwall recurrence of breast carcinoma, or for the diagnosis or treatment of other skin conditions that can benefit from tissue reoxygenation or increased blood perfusion and blood vessel permeability. In addition, other applications may benefit from this applicator's ability to rapidly and uniformly heat large areas of skin and underlying tissue, or from the potential to concentrate microwave power deposition in specific tissue heterogeneities like freckles, hair follicles, scars or tiny tumor nodules. The present invention provides a microwave applicator that can facilitate treatments of, for example, plaque psoriasis, stimulation of bone growth, healing of superficial cuts and abrasion wounds, or concentration of the delivery or heat activation of gene therapy, liposomes, or contrast agents for improved CT or MR Imaging of superficial tissues. Additionally, the microwave applicator may be used to warm surgically exposed organs. Also, the microwave applicator may be configured as an intracavitary applicator to be placed within a body cavity and thus treat tissue and organs located within 1-1.5 cm distance of the cavity wall.
In accordance with one aspect of the present invention, a flexible microwave applicator for heating areas of superficial tissue over contoured anatomy includes a flexible, fluid-retaining compartment having a tissue-engaging surface and an opposite non-tissue-engaging surface. The applicator further includes an antenna array adjacent to the non-tissue-engaging surface that includes at least one flexible printed circuit board having a front metal surface, a dielectric substrate, a back metal surface, and connection apparatus for connecting the antenna array to a power source. At least one dual concentric conductor radiating aperture is included on the front surface and at least one microstrip feed line is included that is in communication with the dual concentric conductor radiating aperture and the connection apparatus. Finally, the microwave applicator includes a flexible attachment material for placement over the antenna array and fluid compartment to allow the microwave applicator to be securely attached to a subject.
In accordance with another aspect of the present invention, the antenna array includes a plurality of dual concentric conductor radiating apertures on the front surface and a plurality of microstrip feedlines in communication with the dual concentric conductor apertures and the connection apparatus.
In accordance with a further aspect of the present invention, the microwave applicator is capable of non-invasively monitoring the temperature of the superficial tissue. In one embodiment, monitoring of the temperature of the superficial tissue is accomplished by providing at least one plastic catheter molded into the tissue-engaging surface and at least one sensor that is placed within or pulled repeatedly through the catheter. In another embodiment, non-invasive temperature measurements of superficial tissue under the applicator are accomplished through radiometric monitoring of temperature dependent signals emanating from the tissue and received by an antenna structure located on the flexible circuit board.
In accordance with various aspects of the present invention, the flexible attachment material is configured such that the microwave applicator is configured in various garment-like forms such as, for example, a vest, a jacket, a blanket or wrap, a sleeve, a cap or hood, or a pair of shorts.
In accordance with yet a further aspect of the present invention, the fluidretaining compartment has a relatively thin thickness in a range of 0.25 cm to 2.5 cm, more preferably in a range of 0.5 cm to 1.5 cm, and most preferably, the housing has a thickness of about 0.5 cm.
Accordingly, the present invention provides a flexible microwave applicator that is capable of being configured to the contour of the anatomy of a patient easily and comfortably. Each dual concentric conductor aperture heats effectively across its face to just outside its perimeter to allow for the apertures to be placed in arrays for uniform heating of large surface areas with generally no hot or cold spots between adjacent apertures. Arbitrarily large antenna arrays may be manufactured inexpensively using ultra-thin and flexible PCB technology that can be wrapped in close conformance around highly contoured patient anatomy. Such a thin PCB array along with the relatively thin flexible fluid-retaining housing or dielectric bolus structure, produces a lightweight heat applicator for improved patient comfort. The outer flexible attachment material, generally an elastic garment, secures the applicator comfortably in place on the patient and allows the patient to sit and/or move short distances around the power source during heat treatment, rather than the prior art's previous restriction to a prone position that generally becomes uncomfortable for patients after less than one hour. This improved patient comfort during treatment helps facilitate longer treatment times, in comparison to prior microwave
Gibson Roy
The Regents of the University of California
Townsend and Townsend / and Crew LLP
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