Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Patent
1991-06-17
1994-10-25
Cohen, Lee S.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
607113, 607116, 607156, A61N 106
Patent
active
053585151
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a microwave hyperthermia applicator for heating a limited environment in a dissipative medium, particularly for heating diseased tissue in the human body.
Hyperthermia as brain tumor therapy places special requirements on the treatment system. High blood flow, particular temperature sensitivity of the healthy brain tissue and the limited possibility for surgical treatment of the tumor necessitate a hyperthermia system which is particularly compact and permits sufficiently high thermal energy deposition in a predetermined and limited region in the brain.
German patent application P 3,831,016.3 (and the corresponding German published patent application DE 3,831,016 A1, published Mar. 15, 1990), discloses microwave hyperthermia applicators, antenna arrangements for locally heating a dissipative medium, the tumor-afflicted human tissue. In this case, the incorporation of line transformers at the end of a coaxial feeder cable for a dipole antenna makes it possible for heating to take place only around the dipole antenna, namely in the diseased human tissue and less along the outer sheath of the feeder cable, namely in the healthy human tissue.
Microwave hyperthermia applicators as disclosed in German Patent Application DE 3,831,016.3 still conduct a considerable portion of electrical energy back over the outer conductor so that the dissipative medium is heated.
Another patent, U.S. Pat. No. 4,700,716, discloses and claims a coaxial applicator arrangement which is excited at a proximal end that is not utilized to heat the environment and is there also provided with a termination including a .lambda./4 sleeve. The thinner region of the subsequent, distal end of the coaxial applicator arrangement then serves to actually heat the environment if the latter is composed of a heatable medium. This applicator is no dipole antenna. Due to the radiation characteristic, it is not possible to heat a narrowly defined region by electromagnetic radiation as precisely as with the dipole antenna arrangement according to the invention.
SUMMARY OF THE INVENTION
It is the object of the invention to improve the structure of the dipole and monodipole applicators disclosed in the above mentioned German Patent Application P 3,831,016.3 so that heating of the dissipative medium remains limited to the region around the antenna.
The object is accomplished according to a first embodiment of the invention by a microwave hyperthermia applicator, having a defined limited distribution of the electromagnetic field, in the form of a dipole antenna which, on the outer sheath of the coaxial feeder cable for the antenna, is provided with a covering to change the impedance, and wherein: the covering below and adjacent the dipole half connected with the outer sheath of the feeder cable, is filled with a predetermined dielectric medium and is a .pi./2 or a .pi. transformer; and the outwardly insulated system composed of the dipole antenna, transformer, and the coaxial feeder cable, forms a defined complex resistance with the dissipative medium that primarily surrounds the dipole antenna so that heating of the dissipative medium is limited directly to a predeterminable area around the dipole, and thus there is no heating of the dissipative medium along the outer sheath of the feeder cable.
The above object is achieved according to a further embodiment of the invention wherein the antenna is a monopole antenna and wherein the covering filled with a dielectric medium is a .pi./2 transformer which is disposed at the same location as the dipole half connected with the coaxial outer sheath of the dipole embodiment, so that the outwardly insulated system, composed of the monopole antenna, the .pi./2 transformer and the coaxial feeder cable, forms a defined complex resistance with the dissipative medium surrounding primarily the monopole antenna so that heating of the dissipative medium is limited directly to a predeterminable area surrounding the monopole, and thus there is no heating of the dissipativ
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Hurter Willibald
Reinbold Fritz
Casler Brian L.
Cohen Lee S.
Deutsches Krebsforschungzentrum Stiftung des Offentlichen Rechts
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