279 Non-invasive imaging biomarkers 3 A colour-coded image superimposed on the greyscale B-mode US images is generated, with colours in the red spectrum representing soft tissues and colours in the blue spectrum representing firm tissues. (Semi)quantitative analysis uses numerical values that correspond to the deformation ratios (strain) or stiffness (sheer wave), scored according to several systems. A meta-analysis by Nell et al. based on 20 qualitative elastosonography studies concluded that elastosonography could accurately diagnose benign nodules with both a pooled sensitivity and a NPV of 99%, thereby safely dismissing FNAC, on condition that only completely soft nodules are classified as benign (benign call rate 14%) [286]. The role of elastosonography in the preoperative workup of cytologically indeterminate thyroid nodules is limited. Qualitative US based on colourscales has insufficient sensitivity and specificity and semiquantitative methods lack validation. A meta-analysis including 20 studies on both qualitative and quantitative techniques and a total of 1.734 indeterminate thyroid nodules reported an overall pooled sensitivity and specificity of 77% and 87%, respectively, with similar diagnostic accuracies for real-time, shear wave and strain ratio elastosonography [411]. The power of the available evidence is negatively impacted by methodological heterogeneity in imaging techniques, image processing, and elasticity scoring methods across studies. Yet, the suggested rule-out capacity of qualitative elastosonography when only completely soft nodules are included is worth validating in indeterminate thyroid nodules, for its easy implementation and potential low costs. Elastosonography can be performed during regular thyroid US with the same equipment, prolonging the procedure only five minutes. To the best of our knowledge, no cost-effectiveness studies have been carried out in indeterminate thyroid nodules, possibly limited by the heterogeneous methodology. Computed tomography CT is a 3D anatomical imaging technique that reflects X-ray attenuation by different tissues. CT scanners use a rotating X-ray tube and an oppositely placed row of detectors placed in the gantry to measure X-ray photon attenuations, which are reconstructed into tomographic images. Contrastenhancement by iodine-based intravenous contrast may be performed to highlight structures such as blood vessels that otherwise would be difficult to distinguish from their surroundings on nativephase CTs, to obtain functional (perfusion) information about tissues and to improve soft-tissue contrast. However, the usage of iodinated intravenous contrast media is relatively contra-indicated as a post-thyroidectomy radioiodine (131I) ablation dose might be indicated in patients suffering from differentiated thyroid cancer. The effectiveness of radioiodine therapy might decrease by recent use of high doses of iodine and an interval of at least one month between iodinated contrast and radioiodine is recommended [412].
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