In this issue, Bulzacka and Makarewicz present “Postablative 131I SPECT/CT Is Much More Sensitive Than Cervical Ultrasonography for the Detection of Thyroid Remnants in Patients After Total Thyroidectomy for Differentiated Thyroid Cancer." They studied 154 consecutive patients without known cancer residues or cervical lymph nodes metastases, undergoing 131I thyroid remnant ablation, 14 to 20 weeks after thyroidectomy for DTC. 131I uptake and thyroglobulin and the location and volume of remnant thyroid by US were recorded.
On days 3 to 4 after ablation (1.7–4.6GBq, 46–124.3 mCi 131I), neck SPECT/CT was performed, and 131I uptake foci were assigned to superior or inferior to the lower margin of thyroid cartilage, with each compartment was subdivided into middle and lateral regions.
131I uptake sites and thyroid remnants detected by US, if congruent with SPECT/CT, were counted and analyzed.
In total, 341 131I uptake foci were found in 150 patients (97.4%) by SPECT/CT and 213 corresponding thyroid remnants in 118 patients (76.6%) by US. Ultrasound detected 30% to 46% of 131I uptake foci in superior lateral regions, 49% in pyramidal lobe/thyroglossal duct area (both P < 0.05), 74% to 77% in inferior lateral regions, and 22% in isthmus (both P > 0.05). Correlation between thyroid remnant volume and 131I uptake was strong (r = 0.79), and that between thyroid remnant volume and thyroglobulin was weak (r = 0.24).
Authors concluded that ultrasound is less sensitive than 131I posttherapy SPECT/CT for thyroid remnant detection in patients after thyroidectomy, especially for remnants located superior to the lower margin of thyroid cartilage.