Intracavitary hyperthermia: construction and heat patterns of individualized vaginal prototype applicators

Patients who have inoperable or previously irradiated cervical recurrences, especially if very confined and alone, pose a challenging problem to the clinician. Low-dose irradiation and hyperthermia seems to be a promising method for salvage treatments in previously treated patients. In order to heat the vaginal apex, individualized prototype applicators utilizing commercial microwave antennas were constructed and tested in muscle equivalent phantom. The technical construction of vaginal applicators followed Pierquin's procedure for gynaecological brachy-therapy moulds: (1) a true negative vaginal print in alginate was made; (2) a positive mould in plaster of Paris was then constructed; (3) a negative vaginal print was produced in plaster of Paris and (4) heat moulding of a 0.1 cm thick sheet of cellulose acetate on the plaster mould was accomplished. Interstitial microwave antennas were inserted within the applicator and kept in place using silk wires or Teflon rings. The external part of the applicator was thermally sealed and protected with silicone. This was particularly useful in cases where an inner cooling system was required. Heat patterns in tissue equivalent phantom materials were determined using non-perturbing probes and infrared thermography. An illustrative clinical case is described.