Technetium-99m-pertechnetate whole-body SPET/CT scan in thyroidectomized differentiated thyroid cancer patients is a useful imaging modality in detecting remnant thyroid tissue, nodal and distant metastases before I therapy. A study of 416 patients.

OBJECTIVE

In this study we aimed to evaluate the role of technetium-99m pertechnetate whole body scan (Tc WBS) with single photon emission tomography/computed tomography (SPET/CT) in detecting remnant thyroid tissue, nodal and distant metastases, in differentiated thyroid cancer (DTC) patients before radioiodine (I) therapy.

SUBJECTS AND METHODS

A retrospective analysis was performed in 416 pathologically confirmed DTC patients with total/near-total thyroidectomy. All patients had undergone Tc WBS, followed by I therapy and post therapy scans, under thyroid hormone withdrawal protocol. Eighteen patients had an additional Tc SPET/CT of certain lesions. Foci of uptake on the Tc WBS and when indicated additional foci on the SPET/CT scan were assessed and compared with findings from post-therapy I scans study which served as gold standard.

RESULTS

The Tc WBS showed a sensitivity and positive predictive value of 79% and 100%, respectively, for remnant thyroid tissue detection, while 60% and 98%, respectively for metastatic lymph nodes evaluation. High specificity (99%) and negative predictive value (93%) but low sensitivity (37%) was found in detecting distant metastases. By adding Tc WBS to Tc SPET/CT findings, 2/18 patients were confirmed as false-positive.

CONCLUSION

Our findings suggested that Tc WBS is a useful imaging modality in detecting remnant thyroid tissue, nodal and distant metastases before I therapy. The additional SPET/CT scan when needed in 18 cases supported the Tc WBS diagnosis.