EVALUATION OF DOSE VARIATION DURING TOTAL SKIN ELECTRON-IRRADIATION USING THERMOLUMINESCENT DOSIMETERS

Purpose: To determine acceptable dose variation using thermoluminescen t dosimeters (TLD) in the treatment of Mycosis Fungoides with total sk in electron beam (TSEB) irradiation. Methods and Materials: From 1983 to 1993, 22 patients were treated with total skin electron beam therap y in the standing position, A six-field technique was used to deliver 2 Gy in two days, treating 4 days per week, to a total dose of 35 to 4 0 Gy using a degraded 9 MeV electron beam, Thermoluminescent dosimeter s were placed on several locations of the body and the results recorde d, The variations in these readings were analyzed to determine normal dose variation for various body locations during TSEB. Results: The do se to flat surfaces of the body was essentially the same as the dose t o the prescription point, The dose to tangential surfaces was within /- 10% of the prescription dose, but the readings showed much more var iation (up to 24%), Thin areas of the body showed large deviations fro m the prescription dose along with a large amount of variation in the readings (up to 22%), Special areas of the body, such as the perineum and eyelid, showed large deviations from the prescription dose with ve ry large (up to 40%) variations in the readings. Discussion: The TLD r esults of this study will be used as a quality assurance check for all new patients treated with TSEB, The results of the TLDs will be compa red with this baseline study to determine if the delivered dose is wit hin acceptable ranges. If the TLD results fall outside the acceptable limits established above, then the patient position can be modified or the technique itself evaluated.