Fijación de radioyodo en huesos maxilares simulando metástasis en pacientes con Carcinoma Diferenciado de Tiroides (CDT): False- Positive images in patients with Differentiated Thyroid Carcinoma. (DTC)

in the whole body scans (wbs) with 131i in the follow-up or treatment of patients bearing dtc it is observed frequently fixation areas of the tracer apparently in relation with salivary glands. these areas generally belong to the salivary glands and are present during the first 48/72 hours, but others are kept during more than 3 weeks. these latter ones were considered as possible uptake in ectopic thyroid cells in the mouth floor, iodized proteins, retention of salivary glands and other assertions. valdivieso et al (cong. arg. biol. med. nuclear, 1996) and gutiérrez et al (slat,chile, 1997) considered that the fixation took place also in maxillary bones probably in areas in relation with dental illness (inflammation, pulpitis, dental caries, perionditis, periapical granuloma, periapical cyst and resorption of surrounding bone seen radiologically as periapical radiolucency). this presumption was sustained for two publications (clin. nucl. med. 1998;23. 747-749, and clin. nucl. med. 2000; 23; 314-315). this end the review of 638 131i wbs carried out between january 1st, 2002 and december 31st of 2007 in 502 patients that were studied for ablation, treatment of metastasis or relapses or follow up. in 31,5% of the patients were observed areas of activity in maxilla. the intensity of concentration of the tracer was 0.3 to 1.2 % of the activity administered. in 10 patients was determinate the effective t ？ and in 5 a panoramic rx of the maxilla and a bone scintigraphy with 99mtc-mdp; there were correlation between both images, the 131i one an the 99mtc-mdp with radiology. the effective t？ mean value was 6,87 days ± 0,94 (s.d.) very close to the physical t ？ of the radioiodine tracer indicating a strongly labeled molecule. in 6 patients treated with high activities of radioiodine (5,55 to 11,1 mbq - 150 to 300 mci) actinic lesions were observed in mouth and lingual mucous membrane, including ulcers. the intensity of the images and of the lesions correlate with the intensi