Thyroid Remnant Estimation by Diagnostic DoseI131Scintigraphy orTcO4-99mScintigraphy after Thyroidectomy: A Comparison with Therapeutic DoseI131Imaging

Abstract

In this clinical study, we have compared routine diagnostic dose131I scan andTcO4-99mthyroid scintigraphy with therapeutic dose131I imaging for accurate thyroid remnant estimation after total thyroidectomy. We conducted a retrospective review of the patients undergoing total thyroidectomy for differentiated thyroid carcinoma (DTC) and subsequently receiving radioactive iodine (RAI) treatment to ablate remnant thyroid tissue. All patients had therapeutic dose RAI whole body scan, which was compared with that of diagnostic dose RAI,TcO4-99mthyroid scan, and ultrasound examination. We concluded that therapeutic dose RAI scan reveals some extent thyroid remnant in all DTC patients following total thyroidectomy. Diagnostic RAI scan is much superior to ultrasound andTcO4-99mthyroid scan for the postoperative estimation of thyroid remnant. Ultrasound andTcO4-99mthyroid scan provide little information for thyroid remnant estimation and, therefore, would not replace diagnostic RAI scan.