RT Journal Article SR Electronic T1 Effect of a Diagnostic Dose of 185 MBq 131I on Postsurgical Thyroid Remnants JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 2038 OP 2042 VO 41 IS 12 A1 Bajén, Ma Teresa A1 Mañé, Salvador A1 Muñoz, Antonio A1 Ramón García, José YR 2000 UL http://jnm.snmjournals.org/content/41/12/2038.abstract AB Stunning of thyroid remnants after diagnostic scanning with 131I may limit 131I therapy. The follow-up scans and serum thyroglobulin levels of such patients have been studied. Methods: Three-hundred seventy-eight patients who underwent thyroidectomy for differentiated thyroid carcinoma were studied. Diagnostic scans were obtained with 185 MBq 131I; 7.2 wk afterward, the patients received 489 ablative treatments with 4 GBq 131I. A total of 1575 scans were obtained (pre- and posttreatment scans and 615 follow-up scans). The evolution of serum thyroglobulin levels was determined. Results: In all patients, the thyroid-stimulating hormone level was more than 30 μIU/mL. Posttherapy scans showed less uptake than did diagnostic scans or even showed negative findings in 99 patients (21%). In these patients, the mean time between diagnostic scanning and therapy was 7.9 wk. In 61 of these 99 patients (61.6%), follow-up scans have shown negative findings, serum thyroglobulin was less than 3 ng/mL, and antithyroglobulin antibodies were not present. Twenty-three patients (23.2%) have not undergone follow-up scanning yet. In 8 patients (8.1%), follow-up scans showed negative findings but serum thyroglobulin was more than 3 ng/mL. In 7 patients (7.1%), follow-up scans showed less uptake than posttherapy scans, but the findings were not yet negative and thyroglobulin was less than 3 ng/mL. Conclusion: Our data suggest that a stunning effect does not exist for doses of 185 MBq 131I for diagnostic scans. However, a therapeutic effect may exist.