Abstract:
Objective To investigate the diagnostic gain value and its effect on clinical diagnosis and treatment of post-therapeutic 131I SPECT/CT imagings in patients with differentiated thyroid carcinoma (DTC).
Methods This retrospective study enrolled 404 DTC patients composed of 89 males and 315 females and aged 21 to 69 (46.3±5.9) years old. The patients took their first 131I therapy at the West China Hospital of Sichuan University between January 2017 and May 2020. All patients were evaluated using SPECT/CT imagings and whole-body anteroposterior position 131I planar scans five days after receiving a dose of 1.11–9.25 GBq. The 131I planar scans and the SPECT/CT imagings were evaluated independently for iodine uptake foci, which were categorized as residual thyroid, lymph node, distant metastasis and the equivocal foci. According to the anatomical location information of CT, the correction ratio of SPECT/CT imagings to the original diagnosis of iodine uptake foci shown by 131I planar scans was calculated. Then, the influence of SPECT/CT imagings on the clinical diagnosis and management of DTC patients was further assessed. McNemar test and McNemar–Bowker test were both used to assess the distribution differences between 131I planar scans and SPECT/CT imagings.
Results A total of 927 iodine uptake foci were detected in the 131I planar scans of 404 DTC patients. According to the images of 131I planar scans, SPECT/CT imagings led to a revision of the original diagnosis in 179 of 927 iodine uptake foci, and 118 iodine uptake foci considered to be indeterminate based solely on the planar images were accurately classified. SPECT/CT imagings has diagnostic gain value for 11.9% (48/404) of DTC patients, and 1.7% (7/404) patients' diagnosis and treatment decisions have changed. The difference between 131I planar scans and SPECT/CT imagings in the qualitative diagnosis of iodine uptake foci was statistically significant (χ2=101.69, P<0.001). Regarding the detection of metastatic cervical lymph nodes, the characterization of the 131I uptake by SPECT/CT was significantly better than that by planar scans (McNemar test, P<0.05).
Conclusion Post-therapeutic 131I SPECT/CT imagings is of positive significance in the diagnostic gain value and diagnosis and treatment of patients with DTC.