The role of Tc-99m SPECT/CT fusion images in diagnosis of autonomously functioning thyroid nodules

Objectives To clarify clinical value of fusion images of SPECT using Tc-99m and MDCT in diagnosis and management of autonomously functioning thyroid nodule (AFTN).

Methods From Aug. 2008 and Nov.2012, 74 patients, who were referred to our institute for an exact diagnosis for hyperthyroidism associated with thyroid module, underwent combined imaging of thyroid scintigraphy and SPECT with TC-99m and MDCT. Thin-slice multi-planar reconstruction images of the thyroid and neck were obtained using a 64-row MDCT with contrast enhancement. Along with volume rendering image (VR) of thyroid and feeding artery, 2D or 3D SPECT/CT fusion images were obtained using a workstation. All patients also underwent US with a 12.5MHz probe and Power Doppler Mode. Findings on Scintigram with SPECT, Power Doppler US, and SPECT/CT fusion images of SPECT/CT were interpreted by 2 experienced radiologists. Diagnostic value of scintigram, US, and SPECT/CT was determined and compared one other.

Results Of 74 patients, 62 had AFTN or AFTN associated with other thyroid disorders (29 solitary AFTN with mostly solid component, 9 solitary AFTN with dominant cystic change, 15 with multiple AFTNs. 6 with both AFTN and non-functioning nodule and 3 with both AFTN and Graves’ hyperthyroidism). The remaining 12 did not have AFTN. The sensitivity, specificity and accuracy of SPECT, Power Doppler US, and SPECT/CT for diagnosing AFTN were 82%*, 83%, 82%** and 71%*, 100%, and 76%**, and 100%*, 100% and 100%**, respectively (*:p<0.01, **:p<0.01). SPECT/CT fusion images yielded high diagnostic performance. Moreover. SPECT/CT exhibited detailed metabolism within the nodules.

Conclusions SPECT/CT fusion images are more accurate than power Doppler US or scintigram and SPECT using Tc-99m in diagnosing AFTN. SPECT/CT fusion images provides valuable information in differentiating AFTN with various clinical presentation from other spectrum of diseases. SPECT/CT fusion images may have an impact on management of the patients with hyperthyroidism with thyroid nodule.