CLINICAL-SYSTEM FOR SIMULTANEOUS EXTERNAL SUPERFICIAL MICROWAVE HYPERTHERMIA AND CO-60 RADIATION

A system for simultaneous thermoradiotherapy was devised to investigat e the possible benefits and/or complications of thermal radiosensitiza tion in human superficial tumours. The system combines the well-known treatment modalities of external 915 MHz microwave hyperthermia and co balt-60 teletherapy. Single waveguide applicators are utilized either attached to blocking trays, so that the gamma beam travels through a w aveguide and into the patient ten face setup), or in a conventional wa y with the microwave propagation Vector orthogonal to the gamma beam ( orthogonal setup). With these setups a radiation fraction can be deliv ered in the middle of a 60-min, noninterrupted hyperthermia treatment. Temperatures and power level are remotely monitored and recorded outs ide the Cobalt room. Extensive measurements and testing showed that th e operation of the hyperthermia system (generator, applicators, thermo metry unit and temperature sensors) was not disrupted by irradiation a nd that the microwaves were confined to the treatment room and did not interfere with the operation of the Cobalt unit, of an adjacent linea r accelerator or of an adjacent radiotherapy simulator. For the en fac e setup the dose distributions induced in solid water phantoms were un iform with the exception of a narrow (<0.5 cm) region under the applic ators' internal probes where 10-18% reduction exists. This dose defect is clinically smoothed using feathering techniques. The system has be en successfully used without technical problems in 51 treatments in 15 patients (18 lesions) in a phase I/II clinical trial. An analysis of the thermal data showed that the temperature distributions achieved du ring simultaneous delivery have the same general characteristics of th ose achieved in conventional sequential hyperthermia with microwaves, and that the steady state distributions are maintained during the time of simultaneous irradiation. The tests performed in addition to the p reliminary clinical experience clearly indicate that this type of comb ined therapy is technically feasible and safe. Here the system for sim ultaneous, external, superficial thermoradiotherapy and the implementa tion tests performed are described in detail. Preliminary clinical exp erience and results are also reported.