[Comparison of 201T1-chloride and 67Ga-citrate in thyroid tumor scintigraphy]

Twenty-five patients with thyroid tumors were examined by 201T1-chloride and 67Ga-citrate scintigraphy heterochronously in our department. All cases showed the cold nodule with 131I or 99mTc-pertechnetate thyroid scintigraphy and each one was given a histological diagnosis after surgery or excisional biopsy. In 15 cases of thyroid carcinoma, 12 (80%) were positive by 201T1-chloride; 4 (26.7%) were positive by 67Ga-citrate. In examining each histological type, 8 of 9 cases of papillary carcinoma (88.9%) were positive by 201T1-chloride. In 1 negative case the tumor was almost completely encysted; however, they were all negative by 67Ga-citrate. In 2 patients with follicular carcinoma, both of them revealed a positive figure by 201T1-chloride, and one of these with oxyphilic cell carcinoma showed a positive figure by 67Ga-citrate. In 1 case of medullary carcinoma there was slight accumulation with 201T1-chloride, but there was no accumulation with 67Ga-citrate. In 3 cases of undifferentiated carcinoma, 2 patients with small carcinoma showed a negative figure by 201T1-chloride. However, they all showed a positive figure using 67Ga-citrate and this medium also disclosed distant metastases of undifferentiated carcinoma. In 10 patients with thyroid adenoma, 3 (30%) showed a positive figure by 201T1-chloride. Histologically, these were all tubular adenoma, but in all cases of thyroid adenoma 67Ga-citrate revealed a negative figure. From the above mentioned results, the following conclusion were reached. Tumors showing a positive figure by 201T1-chloride that elicited negative results using 67Ga-citrate proved to be differentiated carcinoma or low differentiated types of adenoma. Surgery is indicated in these cases. All of the tumors revealing a positive figure by 67Ga-citrate were highly malignant types. If these tumors showed a negative figure when 201T1-chloride was used, undifferentiated carcinoma was suggested. In undifferentiated carcinoma, 67Ga-citrate scintigraphy is a useful procedure in locating distant metastases, in determining the area to be irradiated, and in judging the effect of therapy.