IMAGING OF THYROID

DR. DEV LAKHERA

THYROID

• Anatomy and Embryology

• Imaging modalities

• Congenital thyroid abnormalities

• Nodular thyroid diseases

• Diffuse thyroid diseases

• Thyroid malignancies

Anatomy

• Infrahyoid compartment

• 2-4th tracheal rings

• Pyramidal lobe

• Size: 5 x 2 x 2 cm

• AP diameter > 2 cm

enlarged.

• Isthmus 4-6 mm

Embryology

• Follicular thyroid tissue

• Parafollicular cells

IMAGING

• Plain Radiography

• USG

• CT /MRI

• Nuclear scintigraphy

• 18 FDG-PET

Plain radiograph

• Paratracheal soft tissue mass

• Tracheal shift/narrowing

• Calcification

• Bony destruction

ULTRASONOGRAPHY

Investigation of choice• Diagnostic role (guided FNAC, biopsy)• Therapeutic role –RFA , Alcohol ablation

7.5 to 10 Mhz

• Normal parenchyma – homogeneous medium to high level echoes.• Capsule – Thin hypoechoic line.

Role of USG in thyroid diseases

• Solid vs cystic lesions.

• Benign vs malignant lesions

• Nodule detection when physical examination is unequivocal.

• Thyroid nodules from other cervical masses

Cross sectional imaging CT/MRI

• Detection lymph nodal metastasis

• Extension into adjacent neck and mediastinal tissues.

• Follow up for recurrence

Nuclear Scintigraphy

• Functional information about the thyroid

• Radiotracer :- Oral I-123, I-131 I.v Tc-99m pertechnate

Normal uptake 10-30 %

• Hot /warm /cold nodule

PET scan

• Follow up of thyroid carcinoma

• Metastatic thyroid carcinoma

• Tumors that don’t concentrate radioactive iodine

CONGENITAL THYROID ABNORMALITIES

Aplasia/hypoplasia of one lobe or the whole gland

Ectopic gland

• Radionuclide scans to detect ectopic thyroid tissue.

• Ectopic (sublingual) thyroid

Nodular thyroid disease

• Discrete lesion/s within the substance of thyroid gland• sonographically distinct from surrounding parenchyma• 85% benign

• hyperplasia of gland

Diffuse nontoxic goiter

Two stages • Hyperplasia • Colloid involution

• USG: Diffusely enlarged thyroid gland .

(euthyroid state)

Multinodular goiter

• multiple nodules with hemorrhage , calcification,

scarring and cyst formation

• Ultrasonography:

--Irregular, showing diffuse inhomogeneous echogenicity

or multiple focal hypoechoic nodules.

• On CTAsymmetric with multiple low density areas

Scintigraphy

• Enlarged gland, with heterogeneous uptake

Differentiating featuresBenign Malignant

Internal consistency

Cystic component

Predominantly solid composition

Echogenicity Hypoechoic /iso /hyper

More marked hypoechogenicity

Margins Well marginated Spiculated, illdefined, irregular

Benign Malignant

Sonoluscent peripheral halo

Absent

Peripheral vascularity Intranodal vascularity

Benign Malignant

Wider than taller Taller than wider

Peripheral calcificationScattered echogenic

Micro calcification

Histopathology -colloid goiter

Colloid cyst

Contrast enhanced sonography

• Shows enhancement of septa in malignant nodules in arterial phase

• Benign septae do not show enhancement.

Thyroid image reporting and data system (TIRADS)

• TIRADS 1: normal thyroid gland – 0 %• TIRADS 2: benign lesions – 0 %

avascular anechoic lesion with echogenic

specks

vascular heteroechoic, non-encapsulated

nodules with peripheral halo

TIRADS 3: probably benign lesions <5 %hyper, iso or hypoechoic nodulespartially formed capsule peripheral vascularity..

Suspicious lesions

• TIRADS 4:solid component

high stiffness of nodule on elastography if available

markedly hypoechoic nodulemicrocalcificationstaller-than-wider shapemicrolobulations or irregular margins

• subclassified as 4a, 4b, and later 4c

TIRADS 4a: one suspicious feature

(5-10%)

TIRADS 4b: two suspicious

features(10-80 %)

TIRADS 4c: Three/four suspicious

features(10-80%)TIRADS 5: probably malignant lesions (more than 80% risk of malignancy)TIRADS 6: biopsy proven malignancy

Diffuse Thyroid diseases

Acute infective Acute suppurative thyroiditis

Autoimmune thyroiditis

Hashimoto thyroiditis:Graves diseasePostpartum thyroiditis:Riedel thyroiditis

Subacute Thyroiditis

De Quervain thyroiditis:

Acute suppurative thyroiditis

• USG: Ill defined, hypoechoic, heterogeneous mass • Internal debris • Septa +/-• Lymph nodes

De Quervain thyroiditis (or subacute granulomatous thyroiditis)

• Self limiting

Sonographic appearance

• Poorly defined regions of decreased echogenicity with decreased vascularity in the affected areas.

• Bilateral or unilateral.

Nuclear scintigraphy

• Low uptake thyroid scan in patients with hyperthyroidism is almost diagnostic

Hashimoto’s (chronic autoimmune lymphocytic)

• Most common type of thyroiditis

• Thyroglobulin antibodies

• Hypothyroidism

USG

• Diffuse coarsened echotexture• Hypoechoic micronodules (1-6 mm) • lobules are surrounded by multiple linear

echogenic coarse fibrous septations

• Colour Doppler Normal or decreased flow, but occasionally there might be hypervascularity.

• Lobules are surrounded by multiple linear echogenic coarse fibrous septations

• MRI Areas of increased signal intensity on T2W

Few areas of contrast enhancement

Graves disease

• hyperfunctioning thyroid

• USG – Inhomogenous diffusely hypoechoic gland

• C/D- hypervascular –Thyroid inferno PSV – 70 cm/sec

Nuclear scintigraphy

• Overall increased uptake throughout the enlarged thyroid gland in the Grave's patient.

• CT enlargement of the extra-ocular muscles

Thyroid malignancies

• Most tumors are well differentiated Papillary carcinoma

• Follicular • Anaplastic• Medullary carcinoma • Lymphoma

Papillary carcinoma • Low grade • Lymphatic spread

USG

• Hypoechogenicity

• Microcalcification -Fine punctate

• Hypervascularity

• Lymph nodal

CYSTIC /FOLLICULAR VARIENT

• Heterogenous lesion with internal

calcification

• Bony destruction

• CECT : Heterogeneous enhancement

Cystic variant

• Papillary thyroid carcinoma: atypical.

Follicular carcinoma

USG

• Hypoechoic ill defined lesion with Thick irregular

capsule

• Types:

Minimally invasive Encapsulated

Invasive Not well encapsulated with vascular invasionCentral chaotic vascularity

Medullary carcinoma

MulticentricParafollicular C cells

Ultrasound

• Hypoechoic solid nodules with coarse internal calcifications. • Involved lymph nodes typically calcify.

CT

• Both primary and metastatic lesions usually have irregular dense calcific foci within .

• In the chest, bullae formation and pulmonary fibrosis

Nuclear imaging

• do not concentrate radioactive iodine

FDG-PET

• ~75% (range 60-95%) sensitive for metastatic disease 6

Anaplastic carcinoma

• Fatal- elderly women, long standing goitre

USG• Hypoechoic lesion encasing the

vessels

CTExtent/ calcification / necrosis

Primary Lymphoma

• Old aged femalesHashimotos

Nodular / diffuse

Nuclear: I-131 Cold noduleGallium- Increased uptake

THANK YOU

Reidel’s thyroiditis

• Invasive fibrous thyroiditis• Ultrasound• The thyroid can appear homogeneously hypoechoic with the poor

demarcation of the gland borders as the fibrotic invasion of the adjacent fat or anatomical structures progresses.

• CT• This may demonstrate compression of local structures by an enlarged

thyroid with low attenuation change within areas of the involved thyroid gland.

• MRI• The fibrosing thyroid gland appears low on T1 and T2 and can have a

variable pattern of enhancement.

CT SCAN

• Supine position with neck in hyperextension

• Contiguous 3-5 mm sections from base of tongue to superior mediastinum

• CT-appearance 80 -100 HU because of I content

• CT Perfusion

MRI

• Can be used in conjugation with scintigraphy since gadolinium does not interfere in I uptake.

• MRA

• MRS

• Dynamic MRI