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
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