Abstract: A radio frequency annular phased array hyperthermia system providing a heated focal zone with a diameter of 3 cm or less in a tissue mass includes a plurality of at least 42 radio frequency energy applicators in three rings adapted to surround the tissue mass. A bolus having a dielectric constant is positioned between the energy applicators and the tissue mass. The energy applicators operate at a frequency of at least about 900 MHz. to create the heated focal zone. The circumferential spacing between adjacent applicators in each ring is less than a critical distance and spacing between adjacent side by side rings is also less than a critical distance with such critical distances being interdependent on the frequency of the energy radiated, the dielectric constant of the bolus, the size of the bolus, and the size of the tissue mass.

Abstract: A radio frequency annular phased array hyperthermia system providing a relatively small heated focal zone in a relatively large tissue mass includes a plurality of radio frequency energy applicators in at least one ring adapted to surround the relatively large tissue mass. A bolus having a dielectric constant is positioned between the energy applicators and the tissue mass. The energy applicators operate at a frequency high enough to create the relatively small heated focal zone. The spacing between adjacent applicators in the at least one ring is less than a critical distance and spacing between adjacent rings when the at least one ring is a plurality of side by side rings is less than a critical distance with such critical distances being interdependent on the frequency of the energy radiated, the dielectric constant of the bolus, the size of the bolus, and the size of the relatively large tissue mass.

Abstract: The accuracy of tissue heating in a body when using a phased array hyperthermia system can be improved by using, in conjunction with the hyperthermia system, a program for predicting heating patterns within the tissue based upon a selected E-field value at each of the antenna energy feedpoints. The hyperthermia system includes circuitry necessary to provide information for calculating the complete EM field at each of the antenna feedpoints during treatment, and such calculated actual feedpoint EM fields are feed to the program to be used in place of the otherwise program generated e-fields in predicting the heating pattern produced by the hyperthermia system during treatment. Further initial operating parameters of the hyperthermia system can be set to produce calculated actual EM fields at the antenna feedpoints which approximate the E-field values used by the program in pretreatment optimizing of the heating pattern.

Abstract: Heat treatment is applied to tissue in need of such treatment which is surrounded by tissue not in need of such treatment, by positioning a deposit within the surrounding tissue adjacent the tissue in need of treatment. The dielectric constant and/or the conductivity of the deposit is greater than that of the surrounding tissue. A radio frequency antenna or antenna array directs a radio frequency signal at a selected frequency into the deposit. The deposit has a diameter within a range of about 0.5 times to about 0.16 times the wavelength of the radio frequency signal within the surrounding tissue. The deposit is heated, at least partially through resonant heating, to a temperature greater than the surrounding tissue to apply heat treatment to the tissue in need of treatment. The deposit may take the form of a balloon of a Mammosite® type device to provide hyperthermia treatment in conjunction with radiation treatment of a breast after a lumpectomy.