Comparison of Tl-201 chloride and Ga-67 citrate scintigraphy in the diagnosis of thyroid tumor: concise communication.

Twenty-five patients with thyroid tumors were scintigraphed with both Tl-201 chloride and Ga-67 citrate. All cases showed a focal area of decreased activity with I-131 or pertechnetate (Tc-99m), and each had a histological diagnosis after surgery or excisional biopsy. From the data we conclude the following: (1) Tumors giving a positive scan with Tl-201 chloride but negative results using Ga-67 citrate prove to be differentiated carcinoma or poorly differentiated adenoma. (2) All tumors that are positive with Ga-67 are highly malignant types, and if these tumors are negative by Tl-201, undifferentiated carcinoma is suggested. (3) Ga-67 citrate scintigraphy is a useful procedure in locating distant metastases, in determining the area to be irradiated, and in judging the effect of therapy on undifferentiated carcinoma.