From the Research
The sonographic criteria for the fan sign of the thyroid are not explicitly defined in the provided evidence, however, a comprehensive sonographic evaluation of the thyroid gland should include assessment of thyroid size, echogenicity, vascularity, and identification of any nodules or abnormalities, as well as evaluation of surrounding structures including cervical lymph nodes. When evaluating the thyroid gland, it is essential to use a high-frequency linear transducer (7-15 MHz) with the patient in a supine position and neck slightly extended, covering both thyroid lobes and the isthmus in transverse and longitudinal planes 1. Key sonographic criteria include:
- Assessment of thyroid size (normal adult dimensions: lobes 4-6 cm in length, 1.5-2 cm in width, and 1-2 cm in depth)
- Echogenicity (normally homogeneous and hyperechoic compared to adjacent muscles)
- Vascularity (using color Doppler)
- Identification of any nodules or abnormalities When evaluating nodules, it is crucial to document their:
- Location
- Size in three dimensions
- Composition (solid, cystic, or mixed)
- Echogenicity
- Margins
- Shape
- Presence of calcifications The examination should also include assessment of surrounding structures, including cervical lymph nodes in levels II-VI, to allow for accurate diagnosis of common thyroid conditions such as nodules, goiter, thyroiditis, and potential malignancies 2. Proper patient positioning and technical parameters (appropriate depth, focus, and gain settings) are essential for optimal imaging quality and diagnostic accuracy. It is also important to note that the presence of intrinsic microcalcification is a statistically reliable criterion for increased suspicion of malignancy in thyroid nodules, and nodules with this feature should undergo biopsy, particularly if calcifications have a snowstorm appearance on sonography 3. Additionally, the anteroposterior and transverse diameter ratio of nonpalpable thyroid nodules (A/T) > or = 1 can be a sonographic criterion for recommending fine-needle aspiration cytology (FNAC) 4.