Abstract 24: Role of Strain Elastography in predicting possible malignant nature of thyroid nodules as a companion to TIRADS scoring

Background: Thyroid Imaging Reporting and Data System (TIRADS) scoring is used to assess the nature of nodules in the thyroid gland, especially with regards to the possibility to predict chances of malignancy of those nodules. The commonest used system worldwide is the one by the American College of Radiology (ACR-TIRADS). Majority of thyroid cancers are hard; hence the stiffness evaluation can become part of nodule characterization. Strain or stress elastography is the elastography technique in which the ultrasound probe is placed in front of the thyroid nodule with interposition gel. The beating of the carotid artery generates a sufficient deformation to create a qualitative map image in the region of interest. Addition of strain elastography to the TIRADS scoring can improve the sensitivity & specificity of the modalities in predicting the malignant potential of thyroid nodules. Methods: In this cross-sectional study, among the USG Thyroid cases done in Endocrinology Dept. of a tertiary care hospital in South India, the cases which showed Solitary Thyroid Nodule (STN) among them during 6-month study period were selected. All of them had undergone Strain Elastography (SE) also. The data with regards to the USG nature of those STNs including ACR-TIRADS scoring, & the SE nature of them including Rago scoring, were taken &analysed. Both TIRADS score &Rago score were analysed together. From among those STNs, only those nodules with either TIRADs score 5 or Rago score >2 was included in the detailed analysis because those would be the nodules with more chance of being malignant. All such nodules also underwent USG guided Fine Needle Aspiration Cytology (FNAC) & the report of FNAC was analysed to find whether they belonged to Bethesda Category less than III (benign) or belonged to Bethesda Category III or more (suspicious for malignancy). Results: Out of the total 91 STNs studied, 36 (40%), 40 (44%) & 15 (16%) were of Rago 3/4, Rago 2 &Rago 1 scoring respectively on SE. 10 out of the 91 STNs were of ACR-TIRADS 5 scoring. 2 out of the 7 Rago 3/4 with TIRADS 5 STNs had FNAC showing Bethesda Cat. III or more nature. 2 out of the 29 Rago 3/4 with TIRADS <5 STNs had FNAC showing Bethesda Cat. III or more nature. 1 out of the 3 Rago 1 or 2 with TIRADS 5 STNs had FNAC showing Bethesda Cat. III or more nature. 36 Rago 3/4 STNs on FNAC yielded Bethesda Cat III or more (4/36 = 11.1%). 55 STNs had Rago < 3 score & based on TIRADS criteria only, 18 of them underwent FNAC & Bethesda Cat. III or more was seen in 2 (2/18 = 11.1%). FNACs on the 10 TIRADS 5 nodules showed Bethesda Cat III or more nature was seen in 4 (4/10 = 25%). These results show that even though not needing FNAC study based on TIRADS criteria, those Rago 3, 4 nodules on FNAC have showed to have suspicious result in FNAC. This means that more stiff nodules as represented by Rago 3, 4 scores in SE could be suspicious for malignancy even when they were not suspected to be of so based on ACR TIRADS USG criteria alone. Conclusion: Sometimes when based on TIRADS criteria alone, some STNs with suspicious for malignant nature may be missed; but when Strain Elastography is also added to the same, the chance of detecting stiffer nodules increases, that could have malignant nature. Strain Elastography modality in USG machine needs to be used more along with conventional TIRADS scoring of thyroid nodules.