122Brachytherapy with permanent implant in low-grade gliomas

121 poster Development of a rapid moulage for brachytherapy when dentist's facilities are not available V. Macias, E. Delmastro, B. Baiotto, S. Costantino, S. EmanuellL G. Scielzo, P. Gabriele Radiotherapy Department, Medical Physics Department, Institute for Cancer Treatment and Research, Turin, Italy A technique of high dose rate brachytherapy mould based on thermoplastic mask is introduced for treating patients with superficial carcinoma of the nasal skin. This method is illustrated with a case report. The thermoplastic mask is carefully performed to avoid stretching on nasal area and the target surface is delineated on it. The thickness of the mask is measured and an elasto-gel bolus of the proper thickness (5-10 mm) is placed over it. Catheters are fixed on the top according to the Paris system rules. A three dimensional reconstruction of the catheters is performed from CT and isocentric radiographs with the surface of the tumor marked and a pretreatment optimized dose distribution is calculated. In this case the thickness of the lesion (3mm) was included between the 95% and 85% isodoses (dose per fraction 350 cGy). In vivo dosimetry was performed weekly in order to check any changes in the mask along the fractionated treatment and to ensure that eye's shielding was in the correct place. Previously calibrated TLDs (LiF 100 with dimensions of 3.17 x 3.17 x 0.38mm ~, read with a Harshaw 200 b/c system) were placed on the surface of the tumor and on both eyelids. Small differences on surface tumor dose between pretreatment planning and in vivo dosimetry have been found, maybe due to TLD wrapper (if increases the bolus) and poor spatial resolution of TLD. The average reading of both eyelids has been less than 27 cGy per fraction. This technique seems to be a safe, rapid and inexpensive (50 E vs 400 E) method to perform a skin applicator when dentist facilities are not available.