Contribution of gamma probe-guided surgery to lateral approach completion thyroidectomy

To evaluate the effectiveness of gamma probe performed with technetium Tc 99m-labeled pertechnetate in patients who underwent completion thyroidectomy after pathologic detection of incidental thyroid cancer following subtotal thyroidectomy.

In this prospective study, we evaluated findings from patients with multinodular goiter who underwent gamma probe-guided lateral approach completion thyroidectomy after the pathologic detection of incidental thyroid cancer following subtotal thyroidectomy where partial thyroid tissue was left unilaterally or bilaterally. Patients who underwent the procedure between January 2003 and January 2007 were included. Thyroid scintigraphy; thyroid and neck ultrasonography examinations; and concentrations of thyroid hormones, thyrotropin (TSH), thyroglobulin, and thyroglobulin antibodies were evaluated before the second operation. Patients were administered 3 mCi technetium Tc 99m pertechnetate during anaesthetic induction, and we extracted suspicious thyroid tissue and tissue with activity above background activity levels according to gamma probe. Extracted tissues were evaluated pathologically.

Completion thyroidectomy was performed in 23 patients. Seventy-nine tissue samples were extracted; 49 were thyroid tissue and 30 were nonthyroid tissue. Mean thyroid tissue to background activity ratio (T:B) was 6.4 +/- 3.9 (range, 2-14.3), and mean thyroid bed (after excision) to background activity ratio (Tbed:B) was 1.2 +/- 0.2 (range, 0.8-1.7) (P = .001). Mean T:B and Tbed:B ratios of the nonthyroid tissue were 1.2 +/- 0.3 (range, 0.2-1.7) and 1.1 +/- 0.2 (range, 0.4-1.4), respectively (P = .001). The thyroid tissue T:B ratio was significantly higher than that of non-thyroid tissue (P<.001). Gamma probe labeling contributed to extraction of small amounts of thyroid tissue that could not be viewed by scintigraphy in 43% of patients.

Using gamma labeling, thyroid tissue shows significantly more activity than nonthyroid tissue. Gamma probe helps detect small, residual thyroid tissue that is buried in the scar tissue that cannot be distinguished by scintigraphy; therefore, it assists in the extraction of the maximum amount of thyroid tissue.