99m-technetium-SPECT/US and I-124-PET/US fusion imaging in comparison to conventional diagnostics for the functional assessment of thyroid nodules

Ziel/Aim Side-by-side evaluation of thyroid ultrasound (US) and ⁹⁹m-Technetium-scintigraphy (conventional diagnostics = CD) can lead to uncertainties regarding the correct topographic assignment of thyroid nodules (TN). The aim of this study was to evaluate the feasibility and potential diagnostic overvalue of ⁹⁹m-Technetium-SPECT/US and I-124-PET/US fusion imaging in this field.

Methodik/Methods Patients referred for thyroid diagnostics in a clinical routine setting were included in this study if CD produced equivocal results. After informed consent was given, additional SPECT was performed. The SPECT data were subsequently transferred to a US device for real-time sensor-navigated (based on a magnetic field) 3D US fusion imaging. Hereafter a low-dose I-124-PET/CT was carried out and also transferred for another 3D US scan. Three experienced investigators rated the overall performance of CD, SPECT/US and PET/US according to a 4-point scale and decided if the additional examinations could solve the problems arising from CD. Furthermore, lesion-by-lesion based functional assessment and rating of the confidence in functional assessment (4-tiered) were performed.

Ergebnisse/Results In 70 patients, 201 TN were included. PET/US was superior to CD and SPECT/US in 96% and 86%, respectively. SPECT/US was superior to CD in 84% of the cases. The uncertainties arising from CD could be clarified by SPECT/US and PET/US in 67% and 96%, respectively. Regarding the lesion-by-lesion based functional assessment, 10% (66%), 39% (14%) and 71% (4%) of the 201 lesions were rated with absolute certainty (equivocal or uncertain) on CD, SPECT/US and PET/US, respectively (p<0.001).

Schlussfolgerungen/Conclusions Both 99m-technetium-SPECT/US and I-124-PET/US fusion imaging proofed feasible and helpful in solving uncertainties arising from CD. In particular, I-124-PET/US appears to have the potential to improve the diagnostic accuracy of the functional assessment of TN.