Standard therapeutic approaches for benign thyroid lesions that warrant intervention are surgery for cold and either surgery or radioiodine for autonomously functioning thyroid nodules (AFTN). Image-guided thermal ablation (TA) procedures are increasingly proposed as therapy options for selected clinical conditions. Due to mounting scientific evidence and widening availability, ETA considered it appropriate to develop guidelines for the use of TA in adult patients. TA procedures are well tolerated, but a dedicated training of the operators is required and information on possible complications needs to be shared with the patients. The following factors should be considered when weighing between observation, surgery, and TA for benign thyroid nodules. In solid non-hyperfunctioning nodules, TA induces a decrease in thyroid nodule volume, paralleled by improvement in symptoms. Nodule re-growth is possible over time and may necessitate repeat treatment, or surgery, in a dialogue with the patient. In AFTN, radioactive iodine is the first-line treatment, but TA may be considered in young patients with small AFTN due to higher probability of restoring normal thyroid function and avoidance of irradiation. In cystic nodules, ethanol ablation (EA) is the most effective and least expensive treatment. TA may be considered for cystic lesions that relapse after EA or have a significant residual solid component following drainage and EA. TA should be restricted to benign lesions that cause symptoms or cosmetic concern. Presently, laser and radiofrequency ablation are the most thoroughly assessed techniques, with similar satisfactory clinical results. Microwaves and high-intensity focused ultrasound therapy options remain to be fully evaluated.© 2020 European Thyroid Association Published by S. Karger AG, Basel Recommendation 1. In adult patients with benign thyroid nodules that cause pressure symptoms and/or cosmetic concerns and decline surgery, image-guided TA should be considered as a costand risk-effective alternative option to surgical treatment or observation alone (1, ØØOO).Recommendation 2. We recommend against the use of TA for asymptomatic lesions (1, ØØØO).

Thyroid nodules are very common, while thyroid cancer is rare and has a very good prognosis. Thyroid nodule ultrasound characterization performed by experienced clinicians allows the selection of the tumours to be punctured and guiding fine needle aspiration (FNA). FNA provide cytology information able to differentiate benign tumours from cancer in approximately 80% of cases. However, it remains difficult to identify thyroid cancers with ultrasound imaging, as demonstrated by the very low rate of cancers detected in all of the carried out FNA (approximately 5%). As a majority of thyroid cancers are hard, the stiffness evaluation has become part of nodular characterization. Since 2005, elastography has been used for the evaluation of thyroid nodules; quasi-static elastography was the first technique available and used, at first, an external pressure induced by the probe, which was then replaced by carotid internal excitation allowing improvement in sensitivity. Semi-quantitative analysis allows comparison of tissue elasticities between tissue with elasticity anomalies and normal tissue and provides therefore useful analytic information. Shear wave elastography (SWE) provides a map of the elasticity in a region and allows stiffness quantification of lesions in kilopascals in order to reinforce the predictive value of malignancy. A tumour whose stiffness is greater than 65kPa or for which the stiffness ratio is greater than 3.7 compared to surrounding healthy tissue is highly suspicious. SWE may enable the detection of malignant follicular tumours that currently escape detection by the ultrasound-guided ultrasound/aspiration cytology couple. Lymph node metastasis of papillary thyroid cancer can also be detected by elastography due to its increased stiffness.

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Despite high elasticity values in classic PTC variants, conventional SWE indexes failed to discriminate between benign and malignant tumors in thyroid nodules with IC.

Imaging of thyroid dysfunction is safe and clinically relevant in children. In congenital hypothyroidism (CH), thyroid imaging permits a precise characterization of the aetiology, which is important for genetic counselling and clinical management. CH may be due to thyroid dysgenesis (ectopia, hypoplasia and athyrosis) or occurs in eutopic glands. In the latter, hypothyroidism may be either transient, especially after iodine overload, or due to permanent autosomal recessive dyshormonogenesis. Thyroid scintigraphy (TS) with either ^99mTcO₄ or ¹²³I will identify ectopic thyroid tissue, which is the commonest cause of CH. However, recent reports favour the use of ¹²³I, which enhances the accuracy of the aetiological classification. In cases of eutopic thyroid, the measurement of ¹²³I uptake before and after perchlorate administration evaluates the organification process. At all ages, colour Doppler ultrasound scanning (CDU) is helpful in assessing thyroid volume, in identifying nodules and in characterizing tissue vascularization. TS and CDU images of most paediatric thyroid dysfunctions are presented.