**Comparison between Two Different Scanners for the Evaluation of the Role of 18F-FDG PET/CT Semiquantitative Parameters and Radiomics Features in the Prediction of Final Diagnosis of Thyroid Incidentalomas**

**Francesco Dondi 1,†, Nadia Pasinetti 2,†, Roberto Gatta 3, Domenico Albano 1,\*, Raffaele Giubbini <sup>1</sup> and Francesco Bertagna <sup>1</sup>**


**Abstract:** The aim of this study was to compare two different tomographs for the evaluation of the role of semiquantitative PET/CT parameters and radiomics features (RF) in the prediction of thyroid incidentalomas (TIs) at 18F-FDG imaging. A total of 221 patients with the presence of TIs were retrospectively included. After volumetric segmentation of each TI, semiquantitative parameters and RF were extracted. All of the features were tested for significant differences between the two PET scanners. The performances of all of the features in predicting the nature of TIs were analyzed by testing three classes of final logistic regression predictive models, one for each tomograph and one with both scanners together. Some RF resulted significantly different between the two scanners. PET/CT semiquantitative parameters were not able to predict the final diagnosis of TIs while GLCMrelated RF (in particular GLCM entropy\_log2 e GLCM entropy\_log10) together with some GLRLMrelated and GLZLM-related features presented the best predictive performances. In particular, GLCM entropy\_log2, GLCM entropy\_log10, GLZLM SZHGE, GLRLM HGRE and GLRLM HGZE resulted the RF with best performances. Our study enabled the selection of some RF able to predict the final nature of TIs discovered at 18F-FDG PET/CT imaging. Classic semiquantitative and volumetric PET/CT parameters did not reveal these abilities. Furthermore, a good overlap in the extraction of RF between the two scanners was underlined.

**Keywords:** thyroid incidentalomas; radiomics; texture analysis; 18F-FDG; PET/CT; positron emission tomography; thyroid cancer
