DEEP REGIONAL HYPERTHERMIA - COMPARISON BETWEEN THE ANNULAR PHASED-ARRAY AND THE SIGMA-60 APPLICATOR IN THE SAME PATIENTS

Purpose: Several institutions have accumulated clinical experience wit h the annular array as well as with the Sigma applicator. There exist only limited data in comparison of both heating devices possibly favor ing the annular array over the Sigma applicator with regard to tumor t emperatures and acute toxicity. The objective of this study was to rec ord temperature distributions at identical sites in tumor and normal t issue in the same patients treated with each device. Methods and Mater ials: Eighteen patients with advanced pelvic tumors were treated on su ccessive occasions with regional hyperthermia using the annular phased array applicator usually driven at 60-80 MHz or the Sigma applicator usually driven at 70-90 MHz. In all patients detailed thermal mapping and temperature analysis for tumor and normal tissues could be perform ed. Results: Regardless the device used the acute toxicity was treatme nt limiting in nearly 50% of the treatments. Systemic stress was treat ment limiting in 30% of the treatments with both devices although syst emic parameters (core temperature, heart rate, changes in blood pressu re) were higher with the annular array. The overall mean minimum, aver age and maximum tumor temperature observed were 39.5 +/- 1.0-degrees-C , 40.9 +/- 1.4-degrees-C, 42.7 +/- 2.3-degrees-C for the annular array and 39.3 +/- 0.9-degrees-C, 40.9 +/- 1.4-degrees-C, and 42.5 +/- 1.7- degrees-C for the Sigma applicator. The time-averaged temperatures ach ieved in 20% (T20), 50% (T50) and 90% (T90) of all measured sites were 41.7 +/- 2.1-degrees-C, 40.8 +/- 1.4-degrees-C, 39.9 +/- 1.2-degrees- C for the annular array and 41.7 +/- 1.4-degrees-C, 41.0 +/- 1.3-degre es-C, and 40.1 +/- 1.0-degrees-C, for the S-60. The difference was not statistically significant. With regard to normal tissue temperatures a trend to higher maximum temperatures in the deep muscle and fat tiss ue was evident for the Sigma applicator. The overall minimum and avera ge normal tissue temperatures in the deep muscle and fat tissue and th e rectum and the time-averaged temperatures achieved in 20% (T20), 50% (T50) and 90% (T90) of the measured sites differ not statistically si gnificant. Conclusion: These results indicate that there continue to b e unresolved limitations in achieving temperature elevation in deep se ated tumors of the pelvis with radiative coherent EM wave techniques u sing amplitude and phase steering capabilities without any special opt imization procedure.