<prompt> Answer this question truthfullyWhat is the correlation between Riedels thyroiditis and echocardiography and ultrasound?  <response>: <reason> Ultrasound may be helpful in the diagnosis of Riedels thyroiditis. Findings on an ultrasound suggestive of Riedels thyroiditis include: Hypoechogenicity Thyroid nodule infiltrating adjacent structures Absence of blood flow on Doppler ultrasound 