Endocrine DOI 10.1007/s12020-014-0241-y

ENDOCRINE IMAGING

The peculiar ultrasonographic and elastographic features of thyroid nodules after treatment with laser or radiofrequency: similarities and differences Massimiliano Andrioli • Roberto Valcavi

Received: 19 February 2014 / Accepted: 12 March 2014 Ó Springer Science+Business Media New York 2014

Abstract The aim of percutaneous thermal ablation with laser (LA) or radiofrequency (RFA) is to reduce the volume of benign thyroid nodules. Little is known about ultrasonographic and elastographic appearances of thyroid lesions after treatment. For the first time, we report in detail the main ultrasonographic and elastographic characteristics of thermally ablated nodules and their underlying similarities and differences. Both thermal treatments usually produce a marked hypoechoic area of coagulative necrosis. LA-treated lesions usually become highly heterogeneous due to the presence of cavitations and charring; they then evolve into hyperechoic scars. In RFA-treated nodules, instead, the necrotic area is more homogeneous but presents more irregular margins compared to those observed in LA-treated lesions. Regardless of the thermal method used, vascularity is typically reduced in all treated nodules and stiffness, evaluated with qualitative elastography, increases. In conclusion, ultrasonographic and elastographic appearances of the thermally ablated thyroid lesions differ slightly according to the adopted procedure. Furthermore, they are peculiar, changeable over time, and potentially misleading. Keywords Laser  Radiofrequency  Thermal ablation  Elastography  Thyroid nodule  Ultrasonography

M. Andrioli EndocrinologiaOggi, 00100 Rome, Italy M. Andrioli (&)  R. Valcavi Endocrinology Unit, Department of Surgery, IRCCS, Azienda Ospedaliera Arcispedale Santa Maria Nuova, Viale Umberto1°, 50, 42123 Reggio Emilia, Italy e-mail: [email protected]

The aim of percutaneous thermal ablation with laser (LA) or radiofrequency (RFA) is to reduce the volume of benign thyroid nodules [1–3]. Apart from size reduction of the lesions, little is known about their ultrasonographic and elastographic appearances after treatment [4]. The features of the thermally treated lesions are worthy of mention because, as a result of their peculiarity and changeability over time, they may erroneously confer to the nodule a suspicious appearance. Immediately after ablation, the features of the lesions treated with both techniques, LA or RFA, are poorly evaluable due to tissue infiltration by gas as a result of tissue vaporization. Characteristic cavitations surrounded by a thin layer of carbonized tissue and charring can be observed some weeks after ablation within LA-treated nodules, as a consequence of the positioning of the optic fibers (Fig. 1a) [5]. Usually, a marked hypoechoic avascular area of coagulative necrosis becomes clearly distinguishable from surrounding viable tissue. This area generally presents regular margins due to the uniform heat diffusion from the fibers (Fig. 1b). Over time, cavitations evolve in hyperechoic scars, making the nodule highly heterogeneous [5]. Scars may resemble macrocalcifications, but usually differ due to the absence of posterior acoustic shadowing. Regardless of the thermal method used, vascularity is typically reduced in all treated nodules (Fig. 1b), while stiffness, evaluated with qualitative elastography, increases, with the highest hardness usually corresponding to scars (Fig. 1c). In the RFA-treated nodules, instead, tissue carbonization is a very uncommon event, as dedicated internally cooled electrodes are used. As a consequence, due to the lack of cavitations and scars, RF-treated nodules appear homogeneous. Furthermore, the margins of the necrotic area may

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Fig. 1 Laser-treated nodule: characteristic cavitations surrounded by charring within the lesion (white arrows) a few days after ablation (a). Marked hypoechoic area of coagulative necrosis presenting regular margins, decreased vascularity, and heterogeneity due to central hyperechoic scars without posterior acoustic shadowing (dashed

arrows), 1 year after treatment (b). Stiffness of an ablated lesion (hard mainly blue nodule) evaluated by qualitative elastography (c). Radiofrequency-treated lesion: extensive necrosis area without scars and presenting spiculated margins (dots arrows) (d)

be more irregular compared to those observed in LAtreated lesions (Fig. 1d). Spiculated margins represent the result of the different heat diffusion and of the high ablative power of the RFA ‘‘moving shot’’ technique [2]. In conclusion, ultrasonographic and elastographic appearances of thermally ablated thyroid lesions may differ slightly according to the adopted procedure but are peculiar and very changeable over time due to nodule shrinkage. Furthermore, some of these features, e.g. marked hypoechogenicity, heterogeneity, irregular margins, and elastographic hardness, may be potentially misleading. Therefore, clinicians dealing with nodular thyroid gland should always bear in mind that LA- or RFA-treated lesions are peculiar and may seem suspicious at ultrasonographic/elastographic examination.

References

Ethical standard The patients gave their written informed consent to undergo thermal procedures according to the local Ethics Committee, and the guidelines of the Declaration of Helsinki. Conflict of interest disclose.

The authors have no conflicts of interest to

Financial disclosure

This article did not receive any fund.

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1. R. Valcavi, F. Riganti, A. Bertani, D. Formisano, C.M. Pacella, Percutaneous laser ablation of cold benign thyroid nodules: a three-year study in 122 patients. Thyroid (2009). doi:10.1089/thy. 2010.0189 2. J.H. Baek, Y.S. Kim, D. Lee, J.Y. Huh, J.H. Lee, Benign predominantly solid thyroid nodules: prospective study of efficacy of sonographically guided radiofrequency ablation versus control condition. AJR Am. J. Roentgenol. (2010). doi:10.2214/AJR.09. 3372 3. H. Gharib, L. Hegedu¨s, C.M. Pacella, J.H. Baek, E. Papini, Clinical review: nonsurgical, image-guided, minimally invasive therapy for thyroid nodules. J. Clin. Endocrinol. Metab. (2013). doi:10.1210/jc.2013-1806 4. M. Andrioli, C. Carzaniga, L. Persani, Standardized ultrasound report for thyroid nodules: the endocrinologist’s viewpoint. Eur. Thyroid J. (2013). doi:10.1159/000347144 5. S. Piana, F. Riganti, E. Froio, M. Andrioli, C.M. Pacella, R. Valcavi, Pathological findings of thyroid nodules after percutaneous laser ablation : a series of 22 cases with cyto-histological correlation. Endocr. Pathol. (2012). doi:10.1007/s12022-012-9192-0

The peculiar ultrasonographic and elastographic features of thyroid nodules after treatment with laser or radiofrequency: similarities and differences.

The aim of percutaneous thermal ablation with laser (LA) or radiofrequency (RFA) is to reduce the volume of benign thyroid nodules. Little is known ab...
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