Ultrasound, elastography, and fluorodeoxyglucose positron emission tomography/computed tomography imaging in Riedel's...

Area of Science:

• Radiology
• Endocrinology
• Pathology

Background:

• Riedel's thyroiditis (RT) is a rare, chronic inflammatory thyroid disease characterized by dense fibrosis.
• Imaging features of RT are infrequently published, with no prior reports on ultrasound elastography (USE) findings.
• This study investigates the utility of ultrasonography (US), USE, and FDG-PET/CT in two RT patients.

Observation:

• Two female patients presented with large, hard goiters causing compressive symptoms; one also had retroperitoneal fibrosis.
• US revealed hypoechoic areas, irregular margins, and vascular encasement of the carotid artery and jugular vein thrombi.
• USE demonstrated heterogeneous tissue stiffness, while FDG-PET/CT showed thyroidal uptake foci.

Findings:

• US identified a compressive multinodular goiter with poorly vascularized, hypoechoic areas and irregular margins.
• USE quantified significant heterogeneity in thyroid parenchyma stiffness (21-281 kPa).
• Both patients showed reduced thyroid volume and resolution of vascular encasement after corticosteroid treatment, while FDG-PET/CT findings remained stable.

Implications:

• US features, particularly vascular encasement and response to corticosteroids, may be specific to Riedel's thyroiditis.
• This is the first report documenting thyroid tissue hardness using USE in RT.
• US and USE are valuable tools for assessing RT, complementing FDG-PET/CT, which requires further investigation.