Posttherapeutic (131)I SPECT-CT offers high diagnostic accuracy when the findings on conventional planar imaging are inconclusive and allows a tailored patient treatment regimen.

Purpose: The purpose of this prospective study was to determine the diagnostic impact and influence on patient treatment of posttherapeutic (131)I SPECT-CT when the findings on planar posttherapeutic whole-body scintigraphy (ptWBS) were inconclusive.

Materials And Methods: A total of 53 SPECT-CT scans were performed in 41 patients with thyroid cancer after high-dose (131)I therapy (2.944 to 7.