by Dr Ahmed Refaey FRCR Anatomy of thyroid

by Dr. Ahmed Refaey FRCR

Anatomy of thyroid gland

What are the indications for thyroid ultrasound? u Diffuse enlargement on physical examination u A palpable mass u A non palpable mass seen on other imaging( CT-MRI- nuclear scan) u Abnormal thyroid function tests

Thyroid diseases Diffuse Ø Grave's disease Ø Hashimoto thyroiditis Ø De Quervain's thyroiditis Focal Ø Solitary Ø multinodular

Solitary thyroid nodule u Benign u malignant

General features of the solitary nodule u Solid / cystic u Comet tail sign u Margins u Calcification u Color flow imaging

Solid/Cystic u Nodules with large cystic components are usually benign nodules that have undergone cystic degeneration or hemorrhage , however about 20 -30% of papillary carcinomas also have a cystic component, indicating that not all cystic thyroid nodules are benign.

Comet tail sign One highly specific sign of a benignity of a thyroid nodule is the presence of comet tail sign, signifying a benign colloid nodule. This sign is never encountered in a malignant lesion

Echogenecity u Hyperechoic nodule malignant in 4% u Isoechoic nodule malignant in 26% u Hypoechoic nodule malignant in 63%

Margins Peripheral halo of decreased echogenecity is seen around the nodule. u a complete halo is 12 times more likely to indicate benign lesion u An incomplete halo is 4 times more likely benign than malignant u

Calcification u Peripheral rim calcification and large areas of coarse shadowing calcifications are more frequently seen in benign nodules’ u Fine punctate calcifications due to calcified psammoma bodies are more frequently seen in malignant nodules

Color flow imaging There are three general patterns of vascular distribution of the thyroid nodule: u Type 1 : complete absence of flow signal within the nodule. u Type 2 : exclusive perinodular arterial flow signal u “type 1 and 2” are more common with benign nodules u Type 3 : intranodular flow with or without significant perinodular flow and this type is generally associated with malignant nodules.

Although none of the ultrasound features above is BY ITSELF pathognomonic for malignancy, BUT when it used IN COMBINATION they are very useful in differentiating malignant from a benign nodule

What are the features of a benign thyroid nodule? 1 - completely or nearly completely cystic, especially with echogenic foci with comet tail artifact 2 - echogenic or isoechoic to normal tissue 3 - a complete halo 4 - well described margin 5 - rim or large coarse calcifications 6 - hypovasculrity

What are the features of malignant thyroid nodule? 1 - microcalcifications 2 - irregular margin 3 - marked hypoechogenecity 4 - hypervascularity

Examination of adjacent structures u (1)- CCA and internal jugular vein : the presence of thrombus within CCA or IJV in association with a thyroid nodule is a clue to the malignant nature of the nodule

– spread to adjacent structures; extrathyroid spread including involvement of esophagus, trachea, strap muscles, recurrent laryngeal nerve is another clue to the malignant nature of the nodule u (2)

u (3)u The cervical lymphadenopathy LNs commonly involved are the pretracheal , paratracheal and nodes along internal jugular vein.

MULTINODULAR THYROID ultrasound features: – Solid nodules, frequently isoechoic – well defined margins – Cystic component in 60 % – Heterogeneous internal echopattern with multiple septa , solid and cystic portions. – On color flow imaging the nodules either show type 1 or type 2 pattern

u It is generally believed that malignancy is common in a solitary nodule and that multinodularity is usually associated with benign disease, HOWEVER 10 – 20 % of papillary carcinoma may be multicentric

DIFFUSE THYROID DISEASES • • • Grave's disease Hashimoto thyroiditis De Quervain’s disease

GRAVE’S DISEASE u Diffuse enlarged gland u Color Doppler study is pathognomonic for the disease , revealing hypervascularity which is called “thyroid inferno”. u the peak systolic velocity is more than 100 cm/sec “normal up to 25 cm / sec”

HASHIMOTO THYROIDITIS Three stages: – Acute: enlarged in size and increased vascularity. – Chronic: enlarged gland with multiple linear bright echoes throughout the hypoechoic parenchyma as well as multiple small hypoechoic nodules. – Atrophic; end stage : small atrophic gland. avascular with heterogenous echoes.

DE QUARVAN’S THYROIDITIS u The inflammation does not involve the entire gland but infiltrates the gland in a non homogenous pattern. u The sonographic correlate is a disordered pattern of hypoechoic and hypervascular areas

Evaluation of nodules incidentally detected by U/S u Nodules under 1. 5 cm are followed up by u/s u Nodules over 1. 5 cm are further evaluated by FNA

ILLUSTRATED CASES