A CLINICALLY PRACTICAL ELECTRON CONE FOR THE TREATMENT OF HEAD AND NECK-CANCER

Purpose: The purpose of the work was to develop a practical electron c one and to compare its dosimetry with that of the conventional applica tor collimation system. Methods and Materials: The electron cone consi sts of the upper part of a manufacturer-supplied electron applicator a nd an institution-built rectangular extension tube which produces a 12 cm x 6 cm field at 100 cm SSD while maintaining an air gap of 5 cm be tween the patient. Results: The compact size of the cone allows electr on irradiation without having to reposition the patient after photon t reatment. The radiation field is very similar to that of a standard 15 cm x 15 cm applicator with a 12 cm x 6 cm field restricting insert. R adiation leakage at the surface of the special cone is typically less than 1% of the useful beam at d(max). During 12 years of clinical use the special cone proved itself very practical in the treatment of more than 300 patients. Conclusion: An electron cone practical for clinica l use with dosimetry comparable to the conventional applicator was dev eloped.