Thallium-201 and iodine-131 scintigraphy in differentiated thyroid carcinoma.
The purpose of this study was to determine the concordance and discordance between diagnostic 131I and 201TI whole-body scintigraphy in patients with differentiated carcinoma of the thyroid.


METHODS
Following thyroidectomy for differentiated thyroid carcinoma, 50 patients underwent whole-body 131I and 201TI scanning (60 pairs of scans in total). Fifteen pairs of studies were obtained before ablative therapy, 30 pairs after ablative therapy and 15 pairs after 131I therapy for metastatic disease. Serum thyroglobulin levels were concurrently determined by radioimmunoassay.


RESULTS
Thirty-six 131I whole-body scans (in 34 patients) showed residual uptake in the neck, but only six (17%) of the corresponding whole-body thallium studies had detectable uptake in the neck. Fourteen 131I scans (in nine patients) identified multiple metastatic lesions, whereas the thallium scans were interpreted as either negative, nonspecific or showing fewer lesions. In four study pairs, the thallium scans showed solitary lesions that were not detected by the corresponding radioiodine scans. In 16 scans, the thallium studies gave false-positive results.


CONCLUSIONS
Iodine-131 scintigraphy for differentiated thyroid carcinoma is more sensitive and more specific than 201TI scintigraphy for detection of distant metastases and residual activity in the neck following thyroidectomy.
Lorberboym
M
M
Department of Radiology, Mount Sinai School of Medicine, New York, New York 10029, USA.
Murthy
S
S
Mechanick
J I
JI
Bergman
D
D
Morris
J C
JC
Kim
C K
CK
D018263:Adenocarcinoma, Follicular / Q000000981:diagnostic imaging* / Q000556:secondary; D000231:Adenocarcinoma, Papillary / Q000000981:diagnostic imaging* / Q000556:secondary; D005189:False Positive Reactions; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity; D013794:Thallium Radioisotopes; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D013965:Thyroidectomy; D013997:Time Factors
D007457:Iodine Radioisotopes; D013794:Thallium Radioisotopes