Electron beam dosimetry study of the digits in total body surface irradiation

Total body surface electron beam therapy has been used for treatment of patients with mycosis fungoides. Using a 3 MeV electron beam, four fields and a moving couch technique, it was noted that patients developed marked erythema of the hands with bullous reaction along the lateral aspects of their fingers. Cylindrical phantoms were devised to study thermoluminescent dosimetry of the digits in electron beam therapy. At the lateral surface, dosage as high as 154% of the nominal dose was noted. However, dosage at 3 mm from the periphery was more homogeneous. To exploit the more even dosage at depth, the dosimetry study was repeated with a layer of 2 mm Uvex covering the phantom digits. The variation in surface dose was much reduced without jeopardizing the dose at depth. Uvex hand moulds of 2 mm thickness were constructed for patients on total body surface electron treatment with similar reduction of the much enhanced dose at the lateral borders of the digits.