Methods and apparatus for microwave tissue welding for wound closure
Inventors
Arndt, G. Dickey • Ngo, Phong H. • Phan, Chau T. • Byerly, Diane L. • Dusl, John R. • Sognier, Marguerite A. • Carl, James R.
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-8388613-B1
Publication Date
2013-03-05
Expiration Date
2030-04-09
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Abstract
Methods and apparatus for joining biological tissue together are provided. In at least one specific embodiment, a method for joining biological tissue together can include applying a biological solder on a wound. A barrier layer can be disposed on the biological solder. An antenna can be located in proximate spatial relationship to the barrier layer. An impedance of the antenna can be matched to an impedance of the wound. Microwaves from a signal generator can be transmitted through the antenna to weld two or more biological tissue pieces of the wound together. A power of the microwaves can be adjusted by a control circuit disposed between the antenna and the signal generator. The heating profile within the tissue may be adjusted and controlled by the placement of metallic microspheres in or around the wound.
Core Innovation
The invention provides methods and apparatus for joining biological tissue together using microwave welding technology. One specific embodiment includes applying a biological solder on a wound, disposing a barrier layer on the solder, and locating an antenna in proximate spatial relationship to the barrier layer. The antenna's impedance is matched to the wound's impedance, and microwaves from a signal generator pass through the antenna to weld two or more biological tissue pieces of the wound together. The power of the microwaves is adjusted by a control circuit placed between the antenna and the signal generator.
This method can include using a waveguide coupler to measure forward and reflected powers to ensure proper impedance matching. The antenna's impedance may be adjusted based on these measurements to optimize power transfer. The use of metallic microspheres in or around the wound permits control over the heating profile within the tissue, effectively managing temperature penetration depths during welding.
The problem addressed is that conventional methods for joining biological tissue, such as suturing and stapling, are time-consuming and introduce foreign materials that increase the risk of infection and scarring. Existing suture-less methods employing lasers are difficult to use, require bulky cooling systems, and demand precise solders of uniform depth to avoid tissue damage. Consequently, there is a need for an improved tissue welding system that is portable, reliable, and yields repeatable results.
Claims Coverage
The patent includes three independent claims, each describing methods for joining biological tissue using microwave welding technology with specific features related to impedance matching, power control, and monitoring of microwave transmission.
Method of tissue welding using impedance matched antenna and controlled microwave power
The method includes applying a biological solder on a wound, disposing a barrier layer on the solder, locating an antenna near the barrier layer, matching the antenna impedance to the wound impedance, and transmitting microwaves through the antenna to weld tissue. Microwave power is controlled by a circuit between the antenna and the signal generator.
Method including output and reflected power monitoring of microwaves for tissue welding
Similar to the first method, but further includes measuring output power from the antenna and the power reflected back using respective monitors. Adjustments in microwave power are made based on the ratio of output to reflected power to optimize impedance matching and welding efficiency.
Method with dynamic antenna impedance adjustment based on power reflection ratio
The method involves impedance matching of the antenna to the wound and transmission of microwaves to weld tissue, with continuous measurement of output and reflected power. The impedance of the antenna is adjusted when the ratio of output power to reflected power falls below or equals about 5 decibels to maintain optimal welding conditions.
The independent claims cover methods that involve applying biological solder and a barrier, using an antenna whose impedance is matched to the wound, controlling microwave power through a control circuit, and monitoring and adjusting power and antenna impedance based on forward and reflected microwave power measurements to efficiently weld biological tissue.
Stated Advantages
Provides a tissue welding system that is transportable and reliable with repeatable results compared to conventional suturing or laser systems.
Reduces risk of infection and adverse immunological reactions by avoiding foreign materials such as sutures and staples.
Minimizes disruption to normal tissue growth and cellular organization, thereby reducing scar formation and irregularities in skin.
Allows control of heating profile in tissue using metallic microspheres to manage depth and prevent tissue damage.
Enables simultaneous bacterial ablation while welding by operating at specific microwave frequencies (e.g., Ka-band).
Documented Applications
Closing wounds or incisions by welding two or more biological tissue pieces together, including surface wounds, deep wounds, and wounds on organs such as spleen and liver.
Welding tissue in emergency response or medical procedures where rapid and effective tissue joining is required.
Use in veterinary contexts for wounds on animals of differing sizes, e.g., rodents, dogs, or horses.
Possibility of reducing infection risk by killing bacteria present around a wound during the welding process.
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