Multiparametric Ultrasound Evaluation of the Thyroid: Elastography as a Key Tool in the Risk Prediction of Undetermined Nodules (Bethesda III and IV)-Histopathological Correlation.

The purpose of this study was to select thyroid nodules most at risk for malignancy among those cytologically undetermined by fine-needle aspiration biopsy (FNAB), using B-mode, color duplex Doppler and 2-D shear wave shear wave elastography (2-D-SWE). This was a prospective diagnostic accuracy study with 62 Bethesda III/IV nodules according to FNAB (atypia/follicular lesion of undetermined significance or follicular neoplasia/Hürthle cell neoplasm). Ultrasonography (US) data were compared with resection histologic results, revealing 35 of 62 benign nodules (56.4%) and 27 of 62 carcinomas (43.6%). Conventional US was uses to evaluate nodule echogenicity, dimensions, contours, presence of halo and microcalcifications. Doppler US was used to assess the vascularization (exclusively or predominantly peripheral or central) and mean resistance index of three nodule arteries. Elastography was used to evaluate the nodule elastographic pattern; mean nodule deformation index; deformation ratio between nodule and adjacent thyroid parenchyma; and mean deformation ratio between nodule and pre-thyroid musculature (MDR). Statistical analysis included χ2, Fisher's exact, Student's t, Mann-Whitney tests and multivariable analysis by multiple logistic regression. Areas under the receiver operating characteristic curves (AUC-ROCs) were used for accuracy analysis. Fifty-eight participants (54.7 ± 14.0 y, 51 women) were studied. The parameters that were statistically significant to the univariate analysis were hypo-echogenicity, nodule diameter greater than width and all parameters analyzed from Doppler and elastography. Multivariate analysis revealed that the MDR (in kPa) was the best parameter for risk analysis of indeterminate nodules. Nodules with MDRs >1.53 exhibited a greater chance of malignancy (AUC-ROC = 0.98). We conclude that 2-D-SWE is able to select malignant nodules among those cytologically indeterminate, thus avoiding unnecessary surgery in these cytologic groups.

Ultrasound elastography in the evaluation of thyroid nodules: evolution of a promising diagnostic tool for predicting the risk of malignancy.

The elastic properties of tissue have always been of interest in clinical practice. In the past, the identification of structures that were stiffer on physical palpation would raise the suspicion that "there was something wrong". With the development and advancement of medicine, there proved to be a true correlation in the prediction of malignancy of a lesion: malignant disease tends to stiffen the affected tissue, either by increased cell proliferation or fibrosis. Palpation is the oldest method for the detection of thyroid nodules, which is informed by the knowledge that malignant thyroid lesions tend to be much harder than benign ones. Unfortunately, palpation is a highly subjective method that is dependent on the size and location of the lesion, as well as on the skill of the physician. In cases where these nodules are very small or are located in deep regions, their detection by palpation is difficult or even impossible. In addition, although a malignant lesion differs in terms of elasticity, it may not have echogenic properties, preventing its detection by conventional ultrasound. Imaging that indicates the stiffness or deformation of tissues, through the use of ultrasound elastography techniques, adds new information related to their structural formation. In this article, we review the basic physical principles of elastography and the evolution of the method for the evaluation of thyroid nodules, as well as the limitations of and future perspectives for its use.

A propriedade elástica dos tecidos sempre foi motivo de interesse na prática clínica. A palpação física de estruturas mais rígidas levantava a suspeita de que "havia algo estranho" e isso se mostrou, com o desenvolvimento e avanços da medicina, uma correlação verdadeira na predição de malignidade de uma lesão: a doença maligna tende a enrijecer o tecido acometido, quer por proliferação celular aumentada ou por fibrose. A palpação é o método mais antigo para a detecção de nódulos tireoidianos. Lesões tireoidianas malignas tendem a ser muito mais duras do que as benignas. Infelizmente, a palpação é um método altamente subjetivo e depende do tamanho e localização da lesão e da habilidade do médico. Nos casos em que esses nódulos são muito pequenos ou estão localizados em regiões profundas, a sua detecção por palpação é dificultada ou até mesmo impossível. Além disso, mesmo sendo elasticamente diferente, a lesão pode não apresentar propriedades ecogênicas, impedindo a sua detecção por ultrassonografia convencional. A imagem da rigidez ou deformação desses tecidos acrescenta novas informações relacionadas à sua formação estrutural por meio das técnicas de elastografia. Revisamos, neste artigo, os princípios físicos básicos e a evolução da elastografia para avaliação de nódulos tireoidianos, bem como as limitações e perspectivas futuras do uso dessa técnica.