A new feeding technique for temperature distribution control in interstitial microwave hyperthermia

In microwave hyperthermia for cancer therapy, two power feeding techniques can be utilized: incoherent and coherent operations. In the incoherent operation, not-synchronized microwave pou er is fed into each array element, whereas the coherent operation is achieved by feeding synchronized microwave to the array elements. The authors have been studying the coaxial-slot antenna for interstitial microwave hyperthermia. The antenna is usually employed as an array applicator inserting several antennas into the tissue to generate large heating area. So far we have examined the control of the heating pattern by feeding techniques in order to obtain more uniform and enlarged heating region. Particularly, 'tip-heating,' which means sufficient heating at the area near the tip of the applicator, is significant riot to damage surrounding normal tissue in interstitial hyperthermia. In this paper, two feeding techniques are combined and calculated temperature distributions in a hexagonal array applicator are examined by solving Pennes bioheat transfer equation by finite difference method. As a result, in the coherent feeding;, large heating area was obtained, while better tip-heating was achieved in the incoherent feeding. Moreover. an instance of sequential combination of two feeding techniques is depicted. Tn this case, temperature distribution had both characteristics of large heating area and tip-heating, therefore the ability of the control of heating characteristics by sequential combination of the coherent and the incoherent feedings was presented.