Thyroid & parathyroid

Imaging of Thyroid !!!

Rakesh C A

Development of the thyroid gland• is NOT derived from any of the

pharyngeal pouches• arises from a midline thyroid

diverticulum that forms from the endoderm in the floor of the pharynx just caudal to the 1st pharyngeal arch; these endoderm cells differentiate into the follicular cells of the thyroid gland.

• neural crest cells of the ultimobranchial body migrate into the gland and give rise to the parafollicular cells (aka C-cells) of the thyroid.

• Descends from its place of origin, the foramen caecum at the base of the tongue, to its final location in the anterior lower neck.

• This line of descent is represented by the remnant thyroglossal duct, along which residual thyroid tissue may be found.

• Descent beyond the normal results in a mediastinal component of the thyroid gland

• Anomalies in thyroid development can result in ectopic thyroid tissue and/or cysts present along the course of the thyroglossal duct, which is a midline structure (as opposed to cervical cysts, which are remnants of pharyngeal clefts 2-4 and are found lateral to the sternocleidomastoid muscles).

Anatomy

• 2 lobes and isthmus• Normal

– 5 x 2 x 2 cm– 15 – 35 grams– Average volume – 19.6 ml (males) 18.6 ml (females)

• Pyramidal (accessory) lobe – superiorly from the isthmus or medial aspect of either lobe– Extends superiorly along the distal thyroglossal duct.– visualized in younger patients– Enlarged and readily identified in Graves’ disease

• The thyroid gland is ensheathed by the visceral fascia, a division of the middle layer of deep cervical fascia, which attaches it firmly to the laryngoskeleton.

• The anterior suspensory ligament extends from the superior-medial aspect of each thyroid lobe to the cricoid and thyroid cartilage.

• The posteromedial aspect of the gland is attached to the side of the cricoid cartilage, first and second tracheal ring, by the posterior suspensory ligament (ie, Berry ligament).

• This firm attachment of the gland to the laryngoskeleton is responsible for movement of the thyroid gland and related structures during swallowing.

• Enlarges caudally into the pretracheal space and even upto retrosternal space, anterior to CCAs and IJVs – retrosternal or substernal goitre

Vascular Supply

• ECA STA• TCT ITA• Aortic arch thyroidea

ima

• STV, MTV IJV• ITV BCV

Endocrinology

Clinical manifestations of thyroid disease

• Hyperthyroidism• Thyrotoxicosis• Thyroid storm• Thyroid ophthalmopathy• Hypothyroidism• Secondary manifestations

– compression of trachea, esophagus – respiratory distress, dysphagia

– Compression & displacement of IJV and CCA– Involvement of recurrent laryngeal nerve – vocal cord palsy

Hyperthyroidism vs Thyrotoxicosis

Hyperthyroidism• Sustained thyroid

hyperfunction with increase in synthesis and release of thyroid hormone.

Thyrotoxicosis• Clinical syndrome that

develops when circulating levels of T3 and T4 are increased (TSH is usually supressed)

Thyrotoxicosis with Hyperthyroidism

• Graves’ disease• Toxic multinodular goitre• Hyper functioning adenoma

Thyrotoxicosis without Hyperthyroidism

• Inflammatory thyroid disease

• Ectopic thyroid tissue (ovarian strumii)

IMAGING

Imaging

• Plain radiography• Nuclear scintigraphy• Ultrasonography• Cross-sectional imaging – CT/MR

Plain Radiographs

• Soft tissue radiographs of neck (AP and Lateral)– Enlarged thyroid in pretracheal location– Associated calcification– Tracheal deviation – AP view– Tracheal narrowing – lateral view

• For intubation prior to surgery

• Radiograph of neck & upper chest– Retrosternal extension of thyroid mass– Associated bony destruction

Nuclear Scintigraphy

• Funtional informationM

ajor

Rol

e Hot 8 – 10 %

Warm 15 – 20 %

Cold 15 – 25 %

AgentsAgent Half-life Dose to Thyroid

Gland (rads)Dose

administeredScan timing

I-123 13.5 h 2-8 100-100 Ci PO 4-24 hrs

I-125 60.1 d 80-450 30-100 Ci

I-131 8.05 d 30-100 30-100 Ci PO 24-72 hrs

Tc-99m 6.02 h 0.04-2.0 5-10 mCi IV 15 min

Tl-201 3 d 0.92 2-3 mCi IV 5-10 min

I-131

• High radiation energy (364 keV)– substernal thyroid gland – whole body imaging

after thyroid ablation to detect metastatic foci of thyroid cancer

• Interactions with medications & I-containing contrast agents– Wait for 6 weeks after CT

scan

• Limited spatial resolution

Tc – 99m

• Higher resolution– Preferred for anatomic

imaging

• Distortion with pinhole imaging

• Decreased sensitivity in mediastinum

18FDG - PET

• Follow up of cancers• Metastatic tumors that do not concentrate

radio-iodine• Evaluating patients with rising thyroglobulin

kevels following thyroidectomy

Ultrasonography

• Superficial location of thyroid – Excellent visualisation– Evaluation of anatomy

and pathology

• Generally the first choice investigation

• Spatial resolution – 0.7 to 1 mm– Better than any other

imaging modality

• Advantages:– Accessible– Inexpensive– Noninvasive– Highly sensitive for cystic

vs solid lesions

Technique

• High resolution linear array transducer– 7.5 – 10 MHz

• Supine postion, mildly hyperextended neck• Transverse and longitudinal planes• Lower poles – patient to swallow• Include:

– Carotid artery, jugular vein– Jugular chain of lymph nodes– (superiorly) submandibuar adenopathy– (inferiorly) supraclavicular lymph nodes

• Angle between trachea, esophagus and thyroid gland– Recurrent laryngeal nerve– Inferior thyroid artery

Normal thyroid

• Parenchyma– Homogenous medium to high-level echoes– More hypoechoic – more chances of malignancy

• Capsule – Thin hypoechoic line that bounds the thyroid

gland

Normal thyroid

• Dimensions:– Longitudinal 40 – 60 mm– AP 13 – 18 mm

• Most precise and independent measurement• 2 cm suggestive of underlying pathology• 2.5 cm grossly abnormal

– Isthmus 4 – 6 mm

Normal thyroid

• Volume:• Assess the need for surgery• Calculation of dose of iodine for treatment• Evaluate response to suppression treatments

– Ellipsoid formula (15% error)• Length x width x breadth x 0.52 for each lobe

– Integration of the cross-sectional areas of the thyroid gland, achieved through evenly spaced sonographic scans (5-10% error)

– Three-dimensional (3-D) ultrasound technology

Volume measurement of thyroid gland. A, Transverse, and B, longitudinal, images show calipers at the boundaries of thyroid gland;The calculated thyroid volume is based on the ellipsoid formulawith a correction factor (length × width × thickness × 0.52 for each lobe).

Volume measurement of thyroid gland. C, Images from real-time 3-D study of normal thyroid lobe, visualized simultaneously in axial (top left), longitudinal (top right), and coronal (bottom left) planes. D, Volumetric reconstruction of gland.

Normal thyroid

• Vascularity: – Superior thyroid artery and vein

• Upper pole

– Inferior thyroid vein• Lower pole

– Inferior thyroid artery• Posterior to lower pole of each lobe

• PSV– major thyroid arteries 20 – 40 cm/sec– Intraparenchymal arteries 15 – 30 cm/sec

Normal thyroid vascularity on powerDoppler ultrasound. Normal inferior thyroid vein.

Longitudinal power Doppler image shows a large inferior thyroid vein with associated normal venous spectral waveform.

Ultrasound Elastography

• measures the tissue elasticity

• differentiates between benign and malignant nodule on the basis of consistency of the lesion.– A benign nodule is softer

and hence deforms more easily

– malignant nodule is harder and hence deforms less

Elastogram Scoring• B-mode US image of a nodule is

shown on the top left image , and the corresponding elastographic appearance for progressive increases in stiffness is shown in the other images, ranging from ES 1 to ES 5.

• Nodules with increasing stiffness display an increasing proportion of low strain areas, shown here as red .

• Typically, nodules that display a predominantly low strain pattern equating to ES 3 or above suggest a higher risk of malignancy

ES of 4-5 found to be highly predictive of malignancy with sensitivity of 94%

Limitations

• Benign nodules with coarse calcifications• Cystic lesions with completely liquid contents• Lack of sensitivity for follicular thyroid

carcinoma• Operator dependance• Selection bias• Limited sample bias• Artefacts

Contrast enhanced Ultrasound

Integrated sonographic evaluation (B-mode, color-doppler, elastography and CEUS) of a benign nodule

Integrated sonographic evaluation (B-mode, color-doppler, elastography and CEUS) of a malignant nodule

Cross-sectional Imaging

• Better delineation of lesions within the thyroid• Detection of lymph node metastases• Extension of thyroid disease to adjacent

tissues in neck and mediastinum• Invasion of paraspinal musculature,

esophagus, trachea and carotid sheath structures

Cross-sectional Imaging - Technique

• Supine• Mildly hyperextended neck• Quiet breathing• Suspended swallowing

• 5mm contiguous axial sections (1-3 mm for smaller lesions)

• Base of tongue to superior mediastinum

Normal Thyroid on CT

• At or just below the level of cricoid cartilage• NCCT

– Homogenous attenuation– 80-100 HU (iodine content)

• CECT– Provide additional information about lesions

within thyroid

Perfusion CT

• Functional evaluation of tissue vascularity – tumour angiogenesis

• Benign vs malignant lesions– blood flow (BF)– mean transit time (MTT)

MR Imaging

• Appropriate surface coils– Small field of view– Greater signal to noise ratio– Higher resolution

• Sequences– Non-contrast

• Sagittal, coronal and axial T1• Axial T2 FS

– Contrast (0.1 mmol/kg)• Axial T1 FS

Normal Thyroid on MR

• T1– Homogenous – SI more than neck muscles

• T2– Hyperintense to neck muscles

• Homogenously enhancement

Advantages of MR:

• Gd does not interfere with iodine uptake or organification by thyroid - hence can be used in conjunction with scintigraphy

• Identifies blood vessels (signal voids) that on CT may be confused with lymph nodes

• Excellent soft tissue contrast– Internal parenchyma– Relationship with adjacent structures

• Metastases to regional nodes• Post-operative recurrence (T2 iso to hyperintense) vs scar

tissue (T2 hypointense)

MR Spectroscopy

• Ratio of peaks at 1.7 and 0.9 ppm is able to distinguish normal tissue from carcinoma

• Malignant lesions show:– lipid content (1.7 ppm)– amino acid contents (0.9 ppm)

• All papillary and medullary carcinomas have been found to fall below the ratio of 1.1, while ratio of normal tissue is above 1.1.

• So lesions above 1.1 are considered to be benign.McDermott VG, Spritzer CE (1999) Parathyroid and thyroid glands. In: Stark DD, Bradley WG (eds) Magnetic resonance imaging, 3rd edn. Mosby, St Louis, pp 1807–1820

• The choline peak at 3.22 ppm is mainly due to glycerophosphocholine and glycerophosphoethanolamine that form phospholipids of the cell membranes.

• The choline content rises in malignancy because of rapid multiplication and proliferation of cells. The height of the choline peak depends on the amount and nature of tissues under voxel.

• If there is more necrotic tissue under the voxel, there will be a prominent lactate peak, seen at 1.33 ppm, as a result of anaerobic glycolysis.Evaluation of the Role of Magnetic Resonance Spectroscopy in the

Diagnosis of Follicular Malignancies of ThyroidNikhil Gupta, MS, MRCS(Edin); Binita Goswami, MD, DNB; Veena Chowdhury, MD; L. RaviShankar; Arun Kakar, MS Arch Surg. 2011;146(2):179-182. doi:10.1001/archsurg.2010.345.

Dynamic Contrast Enhancement

• Used to characterise the lesions as benign or malignant

– Type 1 curve- benign– Type 2 curve- indeterminate– Type 3 curve- malignant

DW-MRI

• Significant difference in the ADC values of benign and malignant thyroid nodules has been reported,– Benign having higher ADC values

Follicular carcinoma of the thyroid.

Razek A A et al. AJNR Am J Neuroradiol 2008;29:563-568©2008 by American Society of Neuroradiology

Follicular carcinoma of the thyroid. A and B, Axial T1- and T2-weighted MR images, respectively, showing a well-defined more or less oval mainly solid solitary nodule (arrowheads) affecting the right thyroid lobe with contralateral tracheal displacement. C, ADC map image shows a low ADC value (0.92 ± 0.06 × 10−3 mm2/s) of the thyroid nodule (arrowhead).

Follicular adenoma.

Razek A A et al. AJNR Am J Neuroradiol 2008;29:563-568©2008 by American Society of Neuroradiology

Follicular adenoma. A and B, Axial T1- and T2-weighted MR images, respectively, showing a well-defined more or less oval solitary nodule affecting the right thyroid lobe with contralateral tracheal displacement. The nodule has an anterior cystic part (arrow) and another posterior solid one (arrowhead). C, An ADC map image with marked hyperintensity of the anterior cystic portion of the nodule (arrow), denotes increased diffusion with a measured ADC value of 2.25 ± 0.18 × 10−3 mm2/s and a relatively hypointense posterior solid portion (arrowhead), denotes relatively restricted diffusion with a measured ADC value of 1.2 ± 0.08 × 10−3 mm2/s.

PATHOLOGY

Congenital Abnormalities

• Aplasia• Hypoplasia• Ectopic • Congenital Hypothyroidism

Ectopic Thyroid

• Aberrant descent of the thyroid gland may give rise to ectopic thyroid and thyroglossal duct cyst/fistula.

• Ectopic thyroid can occur anywhere along the line of embryonic descent of the thyroid gland.

• Lingual thyroid gland at the base of the tongue is the commonest type of functioning ectopic thyroid tissue.

A scintigram confirms two foci of ectopic thyroid tissue ( arrow and arrowhead ), seen on ultrasound and CT

On the left, a child with a lingual thyroid. This is the only functioning thyroid tissue that this child has. It would be a disaster if such a 'lesion' were to be excised.

• Ectopic thyroid has also rarely been found in the submandibular and lateral neck regions and may be misinterpreted as metastatic disease.

• Thyroid scintigraphy helps to confirm presence of functioning ectopic thyroid tissue.

• Overdescent of the thyroid may result in ectopic thyroid in lower neck or mediastinum.

• Rarely, thyroid tissue may be found in remote locations, such as within the heart and within ovarian teratomas (struma ovarii)

Thyroglossal duct cyst• Thyroglossal duct cyst is the

most common congenital neck lesion.

• Embryologically, the thyroglossal duct (TGD) extends from the foramen cecum in the posterior third of the tongue, along the fl oor of the mouth to around the hyoid bone and anterior to the strap muscles, down to the thyroid bed anterior to the thyroid or cricoid cartilage.

• The thyroglossal duct usually involutes at around 5–6 weeks of gestational age.

Thyroglossal duct cyst• Any segment of the duct that

fails to regress and subsequently differentiates into an epithelial-lined cyst with persistent secretory activity results in the formation of thyroglossal duct cyst (TGDC).

• It may occur anywhere along the course of the ductal remnant .

• Malignant degeneration (mostly into papillary carcinoma) of the epithelial lining of thyroglossal duct cyst has been reported as a rare (<1%) complication.

• The majority of thyroglossal duct cysts are related to the hyoid bone. – 25–65% occur in the infrahyoid neck, – 15–50% at the level of the hyoid, and – 20–25% in the suprahyoid neck.

• suprahyoid neck are located at the midline, • infrahyoid neck are paramedian in location.

Imaging

• The close relationship of the cyst to the hyoid bone and its location along the expected course of the thyroglossal duct from the foramen cecum down to the thyroid bed is the most important clue to the diagnosis.

4 sonographic patterns:

well-defined anechoic thyroglossal duct cyst (white arrows ). Note its relationship to the hyoid bone ( open arrow )

anechoic thyroglossal duct cyst (white arrows ) with fine internal debris. Note its relationship to the hyoid bone ( open arrow )

4 sonographic patterns:

heterogeneous echo pattern probably due to repeated infection or previous hemorrhage from prior aspiration. Note its relationship to the hyoid bone (open arrow )

uniformly echogenic “pseudosolid” appearance due to the proteinaceous content of the cyst

CT/MR

• CT– Isodense to water– Hyperdense when there is high protein content

• MR– CSF like signal– T1 hyperintense if proteinaceous contents– Enhancement if infected or traumatised

• Nuclear Scintigraphy– No use

• Paramedian thyroglossal duct cyst.

• This lesion not in the midline, but the key finding is that this lesion is cystic and embedded in the strap musculature.

• Thyroglossal duct cyst: axial T1- and T2-weighted images at the level of the hyoid bone

Branstetter B F et al. AJNR Am J Neuroradiol 2000;21:1547-1550

©2000 by American Society of Neuroradiology

Papillary thyroid carcinoma of the thyroglossal duct.

Contrast-enhanced CT at the level of the thyroid cartilage reveals a cystic mass in the anterior neck (arrows), inseparable from the strap muscles (s), with septation and a lobular mural nodule (n).

Complication

Diffuse thyroid disease

• Generalised enlargement of the thyroid without any palpable nodules

• Thyroiditis is infiltration of thyroid with inflammatory cells which may be seen in autoimmune, inflammatory or infectious processes.

• Maybe acute and self limiting or chronic and progressive.• Diagnosis is usually made on the basis of clinical and laboratory

findings and occasionally FNAC.• Sonography is seldom required and when performed it is the

thickness of the isthmus which facilitates the recognition of diffuse thyroid enlargement.

• Normally only a few millimetres thick in AP dimensions.• Maybe cm or more in thickness with diffuse thyroid disease

DIFFUSE THYROID DISEASES

• Acute suppurative thyroiditis• Subacute granulomatous thyroiditis• Hashimoto’s thyroiditis (chronic lymphocytic• thyroiditis)• Painless (silent) thyroiditis• Diffuse nontoxic goitre• Graves’disease• Invasive fibrous thyroiditis• Miscellaneous

Acute suppurative thyroiditis • Rare inflammatory disease usually caused by bacterial infection

and affecting children. • Sonography can be useful in select patients to detect the

development of a frank thyroid abscess. • The infection usually begins in the perithyroidal soft tissues. • On ultrasound images, an abscess is seen as a poorly defined,

hypoechoic heterogeneous mass with internal debris, with or without septa and gas.

• Adjacent inflammatory nodes are often present.• Cross sectional imaging:

– The affected portion of the gland will be enlarged and heterogenous in CT density and MR signal intensity

Subacute granulomatous thyroiditis or de Quervain’s disease

• Spontaneously remitting inflammatory disease probably caused by viral infection.

• The clinical findings include fever, enlargement of the gland, and pain on palpation.

• Sonographically, the gland may appear enlarged and hypoechoic, with normal or decreased vascularity caused by diffuse edema of the gland, or the process may appear as focal hypoechoic regions.

• Although usually not necessary, sonography can be used to assess evolution of de Quervain’s disease after medical therapy.

• NCCT:– Slightly enlarged with lower than normal attenuation

• Scintigraphy:– Low uptake that usually reverts to normal as the patient returns to euthyroid

state.

Focal areas of subacute thyroiditis.

A, Longitudinal power Doppler image of the thyroid gland shows two poorly defined hypoechoic areas (arrow) caused by subacute thyroiditis at fine-needle aspiration.

B, Longitudinal image of a different patient shows poorly defined hypoechoic area (arrows).

C, This area returns to normal on follow-up examination 4 weeks later after medical therapy.

Chronic Autoimmune Lymphocytic Thyroiditis, or Hashimoto’s Thyroiditis

• The most common type of thyroiditis. • typically occurs as a painless, diffuse

enlargement of the thyroid gland in a young or middle aged woman, often associated with hypothyroidism.

• Patients with this autoimmune disease develop antibodies to their own thyroglobulin as well as to the major enzyme of thyroid hormonogenesis, thyroid peroxidase (TPO).

Ultrasound

• The typical sonographic appearance of Hashimoto’s thyroiditis is diffuse, coarsened, parenchymal echotexture, generally more hypoechoic than a normal thyroid.

• In most cases the gland is enlarged.

• Multiple, discrete hypoechoic micronodules from 1 to 6 mm in diameter are strongly suggestive of chronic thyroiditis; this appearance has been called micronodulation.

• Micronodulation is a highly sensitive sign of chronic thyroiditis, with a positive predictive value of 94.7%.

• Histologically, micronodules represent lobules of thyroid parenchyma that have been infiltrated by lymphocytes and plasma cells.

increased flow may indicate an acutephase of the thyroiditis

normal or diminished in most cases of Hashimoto’s thyroiditis

• These lobules are surrounded by multiple linear echogenic fibrous septations.

• These fibrotic septations may give the parenchyma a “pseudolobulated” appearance.

• Both benign and malignant thyroid nodules may coexist with chronic lymphocytic thyroiditis, and FNA is often necessary to establish the final.

A dominant nodule in Hashimoto’s thyroiditis should be considered “indeterminate” and fine-

needle aspiration performed

Hashimoto’s thyroiditis: benign nodule.Longitudinal image shows a discrete hypoechoic nodule (arrows) that proved to be Hashimoto’s thyroiditis at fine-needle aspiration biopsy.Hashimoto’s thyroiditis with papillary thyroid cancer. Longitudinal image shows classic Hashimoto’s thyroiditis (micronodularity) and a hypoechoic dominant nodule (arrow) in the upper pole caused by papillary thyroid carcinoma. A dominant nodule in Hashimoto’s thyroiditis should be considered “indeterminate” and fine-needle aspiration performed.

Hashimoto’s thyroiditis with papillary thyroid cancer.

• As with other autoimmune disorders, there is an increased risk of malignancy, with a B-cell malignant lymphoma most often arising within the gland.

Lymphoma in Hashimoto’s thyroiditis.Transverse image of the left lobe shows diffuse hypoechoicenlargement caused by lymphoma in a gland with Hashimoto’s thyroiditis; Tr, tracheal air shadow.

• CT– Inhomogenous

distribution of iodine– Diffuse moderately

enlarged, lobular thyroid without calcifications, or necrosis

• MR– Areas of increased signal

with low intensity bands on T2

– Regions which enhance more than the remainder of the gland.

• Scintigraphy– No typical pattern– MC heterogenous or patchy

uptake– Uniformly increased or mildly

to severly decreased

• End stage:– Atrophied with increased echotexture (fibrosis)– Blood flow and signals are absent– Occassionally discrete nodules, requiring FNAC

Painless (silent) thyroiditis &Postpartum thyroiditis

• 2 different types of subacute lymphocytic thyroiditis

• Typical histologic and sonographic pattern of chronic autoimmune thyroiditis (hypoechogenicity, micronodulation, and fibrosis),

• but clinical findings resemble classic subacute thyroiditis, with the exception of node tenderness.

• Moderate hyperthyroidism with thyroid enlargement usually occurs in the early phase, in some cases followed by hypothyroidism of variable degree.

• In postpartum thyroiditis the progression to hypothyroidism is more common.

• In most cases the disease spontaneously remits within 3 to 6 months, and the gland may return to a normal appearance.

Diffuse nontoxic goitre

• Diffuse, enlargement of the thyroid associated with euthyroid state

• Characterised by nodularity ,focal haemorrhage, focal calcifications, cyst formation, and scarring may be seen

• Asymmetrical enlargement• May extend substernally and into anterior

mediastinum

Ultrasound• Most patients with

adenomatous goiter have multiple discrete hypoechoic nodules separated by otherwise normal-appearing thyroid parenchyma;

• others have enlargement with rounding of the poles of the gland, diffuse parenchymal inhomogeneity, and no recognizable normal tissue.

• Adenomatous goiter affects women three times more often than men.

Longitudinal dual image shows enlargement of a lobe by multiple nodules

• CT:– Asymmetric with

multiple low density areas reflecting haemorrhage, necrosis or cyst formation.

– Focal areas of hyperdensity reflecting calcifications, haemorrhage or colloid also seen.

• MR:– Spectrum of

appearances– Foci of high T1 signal

• Colloid / haemorrhage

– Heterogeneous on T2

• Nuclear Medicine:– No role in initial

evaluation– Heterogenously iodine

avid, with suppression of surrounding parenchyma when active

99mTechnetium pertechnetate (Tc-99m) scintigraphy image of thyroid gland, of a 48-year-old female patient with multinodular goiter, shows multiple hot (thick arrow) and cold nodules (thin arrow) involving both the lobes of the gland (left>right).

Graves’ disease • Common diffuse abnormality of

the thyroid gland and is usually biochemically characterized by hyperfunction (thyrotoxicosis).

• The echotexture may be more inhomogeneous than in diffuse goiter, mainly because of numerous large, intraparenchymal vessels.

• The parenchyma may be diffusely hypoechoic because of the extensive lymphocytic infiltration or the predominantly cellular content of the parenchyma, which becomes almost devoid of colloid substance.

Hyperthyroidism: Graves’ disease.Transverse dual image of the thyroid gland shows marked diffuse enlargement of both thyroid lobes and the isthmus. The gland is diffusely hypoechoic.

• Color Doppler sonography often demonstrates a hypervascular pattern referred to as the thyroid inferno.

• Spectral Doppler will often demonstrate peak systolic velocities exceeding 70 cm/sec, which is the highest velocity found in thyroid disease.

• Previous studies have shown that Doppler analysis can be used to monitor therapeutic response in patients with Graves’ disease.

• A significant decrease in flow velocities in the superior and inferior thyroid arteries after medical treatment has been reported.

Hyperthyroidism: Graves’ disease.Transverse color Doppler imageof the left lobe shows increased vascularity, indicating an acute stage of the Graves’ disease process; Tr, trachea.

Graves’ disease - Scintigraphy

• Tc-99m scintigraphy image of thyroid gland, of a 32-year-old male patient who presented with neck mass and proptosis, demonstrates enlarged thyroid gland with diffuse increased uptake of the tracer

Invasive fibrous thyroiditis(Riedel’s struma)

• The rarest type of inflammatory thyroid disease• Characterised by fibrosing reaction which

destroys the thyroid and extends into adjacent soft tissues of the neck.

• This disease primarily affects women• Some cases may be associated with mediastinal

or retroperitoneal fibrosis or sclerosing cholangitis.

• The primary reason for sonography is to check for extrathyroid extension of the inflammatory process, with encasement of the adjacent vessels.

• Such information can be particularly useful in surgical planning.

• Open biopsy is generally required to distinguish this condition from anaplastic thyroid carcinoma.

• The sonographic findings in these two diseases may be identical.

Reidel’s struma (invasive fibrous thyroiditis). A, Transverse dual-color Doppler ultrasound image of the thyroid shows a diffuse hypoechoic process in the right lobe extending around the common carotid artery (arrows); Tr, trachea. B, Longitudinal power Doppler image of the right common carotid artery shows a hypoechoic soft tissue mass (arrows) encasing the vessel.

• CT:– Involved thyroid is

hypodense compared to normal thyroid

• MR:– Hypointense on T1 and

T2 (fibrosis)

Reidel’s struma (invasive fibrous thyroiditis). Contrast-enhanced CT scan shows mild enlargement of the right thyroid lobe and soft tissue thickening (arrows) around the right common carotid artery.

Miscellaneous Thyroid Conditions

• Rare inflammatory conditions– Tuberculosis– Sarcoidosis– Fungal diseases– Oppurtunistic organisms (esp in AIDS)

• Amyloidosis, Haemochromatosis– Replace thyroid parenchyma– Decreased signal on T2

• Radiation– Fibrosis and atrophy of the thyroid gland

Nodular Thyroid Disease

• Characterised by presence of one or more palpable or non palpable nodules within the substance of the thyroid gland

• 80-85% due to hyperplasia– 6x in women

• Aetiology:– Iodine deficiency (endemic)– Hereditary familial forms– Poor utilisation of iodine (due to medications)

• “Goitre” – Hyperplasia leading to overall increase in size or volume of the

gland

Sonography in nodular thyroid disease

• Most common sonographically encountered pathology of the thyroid gland

• Discrete lesion, sonographically distinct from the surrounding parenchyma

Role of USG

• Differentiate thyroid nodules from other cervical masses

• Confirm the presence of thyroid nodule when physical examination findings are equivocal

• Distinction between benign and malignant nodules

Benign thyroid nodule on USG• Well marginated cystic or hypoechoic

masses with intenal debris• Comet tail artefacts

– Reliable sign of benignity

• Sonolucent halo around an isoechoic nodule or solid hyperechoic lesion

– Due to perinodular blood vessels and mild edema or compression of the adjacent normal parenchyma

• Nodule with honeycomb appearance • Peripheral or egg shell calcification

– Most reliable feature of benign nodule

• Large and coarse calcifications – more likely to be benign

• Nodule with peripheral vascularity (as against internal vascularity)























































• CT and MR:– MNG appears heterogenous with presence of

cysts and calcifications– T1 – hypointense to normal thyroid– T2 – mixed signal

Benign vs Malignant nodules

When to biopsy?

Biopsy to be done• Hypoechoic nodule with

microcalcifications• Coarse calcifications in a

hypoechoic nodule• Well marginated, ovoid,

solid nodules with a thin hypoechoic halo

• Solid mass with refractive shadowing from the edges (result of fibrosis)

Biopsy not required• Small (<1 cm) colloid filled

cystic nodules• Nodule with honeycomb

appearance • Diffuse multiple hypoechoic

nodules with intervening echogenic bands (Hashimoto’s thyroiditis)

• Homogenously hyperechoic nodule

• ( a ) Transverse gray-scale sonogram of a confirmed papillary carcinoma (arrow). Note that it shows faint echogenic foci ( arrowheads ) within but no obvious posterior acoustic shadowing.

• ( b ) Corresponding power Doppler sonogram with the power gain turned down (resulting in gray-scale ultrasound in the fundamental mode) shows multiple linear posterior acoustic shadows ( open arrows ) arising from the nodule. Tracing back on real-time ultrasound shows these shadows originated from echogenic foci/microcalcification within the nodule.

Pattern based approach• Type 1 or spongiform or honeycomb appearance is characteristic of

colloid nodules and goiter and consists of diffuse internal linear cysts without hypervascularity (iso or avascular)

• Type 2 pattern is a cystic nodule containing a central plug of avascular colloid

• Type 3 or giraffe pattern is typical of Hashimoto’s thyroiditis and is a nodule with appearance of hide of giraffe, i.e. light blocks separated by black bands

• Type 4 or “white knight pattern” or hyperechoic nodule is a variation of type 3 which was found commonly to be a regenerative nodule of Hashimoto’s thyroiditis

• All 4 patterns have been found to have 100% specificity for benignity

Thyroid Incidentalomas

• Small nonpalpable thyroid nodules detected by imaging in an asymptomatic person mostly on CT

• CT features that could distinguish malignancy from benign nodules:– Thyroid nodule with nodular or rim calcifications– AP/Tr ratio > 1.0 (specific CT criteria for malignancy)– Mean attenuation of nodules >130 HU

• Sonographic evaluation to be done if more than 1 criterion

Scintigraphy

• Distinguish cold from hot nodules– Cold nodule – 20% risk– Hot nodule – 5% risk

• Cold nodules usually require biopsy or surgical excision

Management of Thyroid Nodules Detected at USG

Solitary Nodule• > 1 cm with microcalcifications• > 1.5 cm if:

– Solid or almost entirely solid– Coarse calcifications in the nodule

• > 2 cm if:– Mixed solid cystic nodule– Entirely cystic nodule with solid mural component– Substantial growth in the nodule since prior USG

Multiple Nodules

• Consider U/S guided FNAC of one or more nodules on basis of pattern approach

• While the thyroid cancers found in patients with multiple nodules are often in the dominant or largest nodule, in around one-third of cases the cancer is in the non dominant nodule.

Non diagnostic aspirates from initial FNAC

• Second FNAC from the nodule should be considered if it meets the criteria mentioned previously

Presence of abnormal lymph node

• Rounded bulging shape• Increased size• Replaced fatty hilum• Irregular margins• Replaced fatty hilum• Heterogeneous echotexture• Calcifications• Cystic areas• Vascularity throughout the

node

s/o metastatic disease

Prompt biopsy of lymph nodeand/or

ipsilateral thyroid nodule

BENIGN NEOPLASMS

Thyroid Adenoma

• True benign neoplasms distinctly separate from the adjacent thyroid and encased by a fibrous capsule.

• Usually solitary and non functioning• Young and middle aged adults• Usually less than 3 cm, well defined margins• May involute, become cystic or may develop

internal haemorrhage, necrosis, calcification or fibrosis

Imaging

• USG:– Mostly hyperechoic or isoechoic with hypoechoic

peripheral halo (due to fibrous capsule and blood vessels)

• CT:– Solid or cystic (when degenerated)

• MR:– T2 – hyperintense, often heterogenous

• Scintigraphy:– Standard imaging– Hot nodule in 50% cases– 20% Cold nodules are

malignant

Tc-99m scintigraphy image of thyroid gland, of a 47-year-old female patient with a palpable left-sided neck mass, demonstrates an ill-defined area of increased activity in left lower pole consistent with hot nodule (arrow).

• Various subtypes (according to charater and pattern of cell proliferation) include:– Fetal adenoma– Hurthle cell adenoma– Embryonal adenoma

• FNA cannot distinguish follicular adenoma from carcinoma and needs histopathological examination (capsular or vascular invasion)

MALIGNANT NEOPLASMS

• Most common endocrine cancer• Arise from follicular and parafollicular cells

Frequency

Imaging in malignant neoplasms

• Scintigraphy:– Cold nodules 4x risk of malignancy

• USG:– 75% - hypoechoic – 23% - isoechoic– 2% - hyperechoic– Purely cystic or completely hyperechoic – very

rarely malignant

Role of cross sectional imaging

• NOT in characterisation of intrathyroid lesion

• Assessing the findings related to thyroid mass– Invasion through the thyroid capsule– Infiltration through the adjacent tissues and

structures in the neck– Identify cervical lymph node metastases

• Enlarged nodes• Nodes with extracapsular spread• Clustered nodes

• None of the imaging modalities can reliably predict malignant thyroid histology!!!

Papillary Carcinoma

• Most common type of thyroid cancer• Low grade malignancy• Female adolescents and young adults• Excellent prognosis• Poor prognostic factors include:

– male sex, – Increased age (> 45 years), – large tumor size (>3 cm), – Presence of vascular invasion, – presence of extraglandular extension and – poor differentiation on histopathology.

• The tumor commonly spreads along the rich lymphatics in and around the thyroid gland, accounting for the multifocal nature of the tumor within the thyroid gland and its propensity to metastasize to regional lymph nodes.

• Venous invasion occurs in 7% of papillary carcinomas, and distant metastases to bone and lung are seen in 5–7%.

USG – Primary tumour

• Predominantly hypoechoic (77–90%) due to the closely packed cell content and sparse colloid within the tumour.

• Margin of nodule is ill-defined and irregular, indicating its infiltrative nature.

• 10–20% is multifocal on ultrasound.

• Mostly solid (70%).

USG – Primary tumour

• 13–26% have a cystic component, but a predominantly cystic appearance is uncommon.

• In cystic papillary tumours with septa or solid components, vascularity and punctate calcifications may be seen in the solid component/septa, contrary to the findings in benign cystic nodules where the solid portion/septa are usually avascular.

• Presence of punctate micro calcifications is seen in 25–90% and corresponds to calcified psammoma bodies on histology.

• These punctate microcalcifications may not exhibit posterior acoustic shadowing, and increasing transducer frequency/scanning in fundamental mode may help to detect fine shadowing.

• In diffuse sclerosing variant, apart from the primary papillary tumour, there are diffuse, scattered microcalcifications in both lobes with a “snowstorm” appearance.

• 90% shows chaotic intranodular vascularity within the tumour on power Doppler examination.

• Frank tumour invasion ± vascular involvement is occasionally seen on ultrasound in locally advanced disease .

Papillary carcinoma invades muscle

Metastatic regional lymphadenopathy

• Distribution in the pre/paratracheal regions and along the cervical chain.

• Lymph nodes are hyperechoic relative to muscle in 80%.

• Presence of punctate or coarse microcalcifications in 50%.

• Cystic necrosis in 25%. • Thick-walled cystic node or

a cystic node with a solid component





• Cystic necrosis in 25%. • Thick-walled cystic node or a

cystic node with a solid component





• Cystic necrosis in 25%. • Thick-walled cystic node or a

cystic node with a solid component

• Haematogenous spread to lungs, bone and CNS may occur.

• These carcinomas concentrate radioiodine, scanning with 131I following thyroidectomy may be valuable in detecting residual/recurrent thyroid disease in the operative bed of the neck as well as in detecting distant metastases.

• Subsequently treatment with 131I may be performed.

Follicular variant of Papillary thyroid cancer (FVPTC)

• Second most common variant of thyroid carcinoma

• Different from conventional PTC– Larger in size– More round to ovoid than tall in

shape– Iso or hypoechoic with a

hypoechoic halo and the absence of calcification

– Lower incidence of lymph node metastasis and capsular invasion as well as higher rates of lung and bone metastases

Follicular Carcinoma

• 5% of all thyroid cancers• Well differentiated or moderately differentiated• Relatively low grade malignancies• More common in the setting of iodine deficiency• 2-3x in women• Slightly older age group then PTC

2 variants:

• Minimally invasive form– Capsule seen– Better prognosis– Focal invasion of blood vessels of capsule on histology (diff

from follicular adenoma)• Widely invasive form

– Not well encapsulated– Invasion of vessels and adjacent thyroid

• Both forms spread via blood stream > lymphatics• Distant metastases to bone, lung, brain and liver >

cervical lymph nodes

Imaging - USG

• Hypoechoic mass in 45%; isoechoic in remainder.

• Nodule with irregular borders• Heterogeneous internal echoes• Thick irregular capsule• Tortuous intranodal and perinodal

vessels• Vascular and extracapsular invasion

Raises possibility of malignancy of the tumour

Follicular neoplasms: benign and malignant in same patient. Left lobe, and right lobe, of the thyroid show round, homogeneous hypoechoic masses that appear identical except for size differences on transverse images;The larger mass was benign and the smaller mass malignant.

Imaging - Doppler

• Most of the follicular carcinomas have a central flow with moderate increase of intranodular vascularisation on PDS.

• In contrast, follicular adenomas have been shown to have a predominant rim of color flow on PDS.

• However, these cannot be used to rule out malignancy as 20% of malignant nodules have peripheral flow

• Higher RI (> 0.75) is noted in malignant nodules– Characteristic presence of large number of stenoses,

occlusions and fistulas in the neovascularisation

Imaging – CT/MR

• Solid mass similar to PTC• Useful in demonstrating:

– Invasion of adjacent structures– Extension into mediastinum– Cervical lymphadenotpathy

Imaging – Nuclear medicine

• Follicular carcinomas concentrate 131I and hence useful in follow up.

Folicular carcinoma. Tc-99m scintigraphy image of thyroid gland,of a 55-year-old female patient with a palpable right sided neck mass, reveals a large non-functioning cold nodule in right upper pole (arrow).

Prognosis

• Poorer as compared to PTC• Worse for invasive variants than encapsulated

variants

Hurthle cell neoplasm• Variant of follicular vs papillary

neoplasm• a.k.a Oncocytic or oxyphilic

neoplasms– Tumor contains at least 75%

Hurthle cellsand a paucity of colloid cells

• Wide spectrum of sonographic appearances– Predominantly hypoechoic to

hyperechoic– Peripheral blood flow to extensive

internal vascularity

• Hence, differentiation between benign and malignant needs FNAC

Medullary Carcinoma

• 3–5% of all thyroid cancer. • May occur sporadically in middle aged females.• It has a familial form which accounts for 10–20%

of all cases and usually affects several family members.

• It is inherited as an autosomal dominant trait and associated with other endocrine neoplasm.

• Multiple endocrine neoplasms (MEN 2a and MEN 2b) may contain medullary carcinoma and phaeochromocytoma as one of their components.

• The disease is multicentric and/or bilateral in about 90% of the familial cases

• Medullary carcinoma is believed to be derived from C-cells and is thus associated with development of calcitonin.

• The tumour contains stromal amyloid and arises in the lateral upper 2/3 of the thyroid gland.

• Elevated plasma calcitonin levels form the basis of diagnosis and follow-up of recurrent disease.

Imaging - USG• Location: focal hypoechoic mass in lateral upper 2/3 of the gland

(where C-cells are supposedly concentrated) in the sporadic form and diffuse involvement of both lobes in the familial form.

• Solid hypoechoic nodule• Frequently well-defined, may have ill-defined border.

Imaging - USG• Presence of echogenic foci in

80–90% of tumours which represent deposits of amyloid and associated calcification.

• The calcifications are denser than in papillary carcinoma and many show frank posterior acoustic shadowing.

• Similar calcific deposits are also seen in 50–60% of associated nodal metastases.

• Extensive vascularity within the tumour.

Hypoechoic solid nodule with fine internal calcifications

Hypoechoic solid nodule with coarse internal calcifications

Imaging – CT/MR

• Demonstrate a solid mass

• Helpful in displaying surgical anatomy and adjacent lymphadenopathy

Imaging – Nuclear medicine

• Does NOT concentrate radio iodine.• However, radionuclide specific for

neuroendocrine tissue such as 131I-MIBG has been used with some success to evaluate primary as well as metastatic medullary thyroid carcinoma

Anaplastic Carcinoma

• Highly aggressive and rapidly fatal• Elderly women• Usually large at presentation (>5 cm). • Grow rapidly, and compress and invade the

aerodigestive tract and vessels• Lymphatic metastasis may occur but instead

they are more prone to aggressive local invasion of muscles and vessels.

• Worst prognosis

Imaging - USG• Hypoechoic tumour diffusely involving the entire lobe or gland.• Presence of areas of necrosis in 78% and dense amorphous

calcification in 58%. • Often seen against a background of nodular goitre (47%).• Extra capsular spread (trachea, larynx, oesophagus and recurrent

laryngeal nerve) and vascular invasion (common carotid artery, IJV) in a third of patients.

• Multiple chaotic small vessels on colour flow, however, necrotic tumours may be hypovascular (due to vascular infiltration and occlusion by tumour).

• Nodal or distant metastases in 80% of patients. • Metastatic hypoechoic lymph nodes with cystic necrosis are

present in 50% and may show abnormal vascularity.

a ) Clinical photograph of an elderly patient presenting with a rapidly enlarging left anterior neck mass. ( b ) Transverse and ( c ) oblique gray-scale ultrasound of the thyroid gland show a large, solid, heterogeneous, hypoechoic mass with calcifi cation involving the entire left lobe of thyroid gland ( arrows ). Note the presence of extracapsular tumor spread beyond the posterior capsule of the left lobe ( arrowheads ) and metastatic lymphadenopathy ( open arrow ). Asterisk – left common carotid artery, curved arrow – trachea. ( d ) Corresponding power Doppler examination in oblique plane reveals chaotic intranodular vascularity within part of the thyroid tumor ( arrows ) and metastatic node ( open arrows ). Note part of the thyroid mass is avascular which may be due to occlusion of vessels by the malignancy

Imaging

• CT/MR:– Calcification and

necrosis– Demonstrate more

accurately the extend of the disease.

• Nuclear Medicine– Do NOT concentrate

radio-iodine

Imaging

• Nuclear Medicine– Do NOT concentrate

radio-iodine

Lymphoma

• Lymphoma may arise primarily from the thyroid gland or involve the thyroid gland secondarily as part of a systemic lymphoma.

• Primary thyroid lymphoma is a rare tumor and accounts for 1–5% of thyroid malignancies and less than 2% of extranodal lymphomas.

Primary Lymphoma

• Uncommon• Elderly women with long history of goiter• Patients with Hashimoto’s thyroiditis (NHL

type)

• Presents with enlarging thyroid mass and symptoms of compression of aerodigestive tract

Imaging - USG

• Solitary hypoechoic lobulated mass with gland enlagement

• Diffuse, thyroid enlargement, hypoechoic gland with lobulated contours.

• Unilateral/bilateral, enlarged, solid noncalcified nodes.

a ) Transverse gray-scale ultrasound shows diffuse lymphomatous involvement of the left lobe of thyroid gland, which is replaced by a large solid, hypoechoic mass (arrows).

( b ) The mass is hypervascular on corresponding power Doppler examination.

( c ) Longitudinal power Doppler ultrasound of the right lobereveals another area of lymphomatous involvement( arrow ) in the upper pole. Note the abnormal vascularitywithin the lesion.

Imaging – CT/MR

• Hypodense on CT• MR – T1 isontense & T2

hyperintense• Enhances less compares

to other tumors

• Cannot reliably distinguish between Hashimoto’s thyroiditis and lymphoma

Axial contrast-enhanced CT in the same patient better defines the extent of lymphomatousinvolvement in both lobes of thyroid gland (arrows) and its relationship to adjacent structures such as left common carotid artery (arrowhead), compressed left internal jugular vein (curved arrow), and thyroid cartilage (open arrow)

Imaging – CT/MR

• Hypodense on CT• MR – T1 isontense & T2

hyperintense• Enhances less compares

to other tumors

• Cannot reliably distinguish between Hashimoto’s thyroiditis and lymphoma!!!

Imaging – Nuclear Medicine

• Cold – Iodine & Technitium

• Hot – Gallium scans

Thyroid Metastases• late in the course of the disease and

as part of disseminated metastases• MC primaries:

– Melanoma, kidney, bronchus, breast

• Solitary– homogeneous, hypoechoic,

noncalcified, well-circumscribed mass predominantly in the lower pole.

• Multiple– hypoechoic, well-defined, solid,thyroid

nodules.– Metastatic nodules may show diffuse,

disorganized vascularity.

• Diffuse– heterogeneous parenchymal

echopattern, ± thyroid enlargement.

• Metatases from RCC is hypervascular

• Metastases should be considered when histology of the resected thyroid mass is atypical

Thyroid metastasis from renal cell carcinoma. A, Longitudinal (gray scale), and B, power Doppler, images show a 1-cm solid vascular mass.

Poorly Differentiated Carcinoma• This group of thyroid carcinomas includes tumours with a histologic

pattern between differentiated and undifferentiated thyroid cancers.• Insular carcinoma is the best described tumour in this group and has

a female predominance with a median age of 55 years. • Patients commonly have distant (36%) and regional metastases

(26%) at presentation.• On ultrasound, their appearances are similar to other thyroid

cancers (i.e., solid, hypoechoic, ill defined with a heterogeneous echo pattern).

• They may be associated with internal jugular vein thrombosis, malignant neck nodes , and chest, liver and bone metastases.

• The prognosis of insular carcinoma is poor, and the treatment of a pure insular carcinoma is similar to undifferentiated carcinomas.

Note the typical appearance of a malignantthyroid mass ( a , b : calipers ), i.e., ill-defined, solid, markedly hypoechoic lesion with absent flow in the internal jugular vein ( c : arrowheads ). Also note the associated nodal (d:calipers) and lung metastases (e:arrows).

The tumor histology and tumor thrombus within the IJV and middle thyroid vein were confirmed at surgery ( f and g )

Postoperative Disease Surveillance

• Accurate surveillance for possible tumour recurrence in patients treated with total thyroidectomy with/without lymph node dissection is the major goal of long-term follow-up in patients with thyroid cancer.

• Although differentiated thyroid cancer is typically an indolent disease with a high rate of cure, recurrence is common (15–30%).

The risk of recurrence is stratified into:Low-risk patients Intermediate-risk patients High-risk patients

No local or distant metastases

Aggressive tumour histology or vascular invasion

Incomplete tumour excision

All macroscopic tumour has been resected

Microscopic perithyroidal tumour invasion

Macroscopic tumour invasion

No local / regional or vascular tumour infiltration

Neck node metastases Distant metastases

Tumour does not have an aggressive histology

131 I uptake outsidethyroid bed after thyroid remnant ablation

Thyroglobulinemia disproportionate to posttreatment scan

No 131 I uptake outside thyroid bed on firstpost–treatment whole body RAI scan

Approach

• Clinical examination– is essential to detect any obvious tumor recurrence or raise

the suspicion of probable recurrent tumor. • Biochemical markers

– serum thyroglobulin for well-differentiated thyroid cancer– serum calcitonin for medullary thyroid carcinoma).

• Imaging – Integral role in assessment of early recurrent tumor (local,

regional nodal and metastatic disease) – ultrasound, radionuclide imaging including 18 FDGPET among

the most useful imaging tools for disease surveillance

Role of USG

• evaluates the postoperative thyroid bed and the neck for presence or absence of any disease.

• guidance for directed fine needle aspiration of suspicious lesions

( a ) Transverse gray-scale ultrasound in apatient with history of total thyroidectomy for papillary carcinoma. Note the solid, ill-defined, hypoechoic nodulein the postoperative bed on the right (arrow). This is proven to be a nodal recurrence. Note its relationship to the trachea (arrowheads) and the empty left thyroid bed(open arrow).

( b ) Transverse gray-scale ultrasound inanother patient with history of total thyroidectomy for papillary carcinoma. Note the solid, ill-defined, hypoechoicnodal recurrence ( arrow ) anterior to the right common carotid artery ( asterisk ). Also note the recurrence in thepostoperative right thyroid bed (open arrow)

Role of Nuclear Medicine

• Radioiodine whole-body scan (WBS) – high-risk patients – those with elevated TSH-stimulated thyroglobulin

level.• 18 FDG-PET

– detection and localization of recurrent tumor in hyroglobulin positive, radioactive iodine (RAI) scan-negative patients.

INTERVENTION

Percutaneous Aspiration & Biopsy

• Direct biopsy – palpable nodules• U/S guided aspiration / biopsy

– current mainstay of evaluation of thyroid nodules and lymphadenopathy.

Short axis method Long axis method

Guidance for Percutaneous Treatment

• Alternative treatment in the management of cystic thyroid nodules in which malignancy is ruled out.

• Recurrence rate is high in simple aspiration.• Following complete aspiration of the cyst fluid, 30 to

60% of the aspirated volume of sclerosing agent (95% sterile ethanol) is injected.

• Subsequently reaspirated within 1 or 2 days.• Procedure can be repeated in large cystic cavities.• Well tolerated by patients • 72 to 95 % success rate

Ethanol treatment of large colloid cyst

A, Transverse image shows large colloid cyst with needle. Injected ethanol appears as low-level echoes (E); B, Follow-up image 1 month later shows that the large cystic component has mostly resolved, leaving a slightly enlarged residual gland (arrows).

• Autonomously functioning nodules are generally treated by surgery or radioactive iodine therapy.

• Recent reports describe their successful treatment with 95% ethanol injection.

• Ethanol causes direct cell damage by cell dehydration followed by immediate coagulation necrosis and subsequent fibrotic change.

Complication• Inadvertent injection into

recurrent laryngeal nerve – vocal cord paralysis

Indications• Older patients• Pregnant patients• Those in whom surgery is

contraindicated• Patients with large

autonomous nodules (>40ml)

• PEI is also tried in treatment of cervical nodal metastases from papillary carcinoma.

A, round, 1.6-cm, pathologic-appearing node with moderate vascularity.

B, The tip of a 25-gauge needle (arrow)is in the lymph node.

C, The ethanol effect is visible as a focal hyperechoic area (arrow) at injection and is caused by microbubblesthat form from the interaction of ethanol with the tissues.

D, Follow-up power Doppler image 6 months shows that the lymph node has dramatically decreased in size (0.4 cm) and is no longer vascular

Ethanol treatment of thyroid metastasis in a cervical lymph node.

Radiofrequency Ablation in Thyroid Nodules

• Autonomously functioning thyroid nodules– large nodules causing compressive symptoms. – significant decrease in size (≥50%) of the treated lesions was

reported in all cases, and – complete normalization of thyroid function was achieved in

24% to 44% of patients.• Solitary Solid Benign “Cold” Thyroid Nodules

– significant volume reduction of the treated nodules without adverse effects has been reported at follow-up,

– studies with longer follow-up are needed to assess efficacy and safety

Interstitial Laser Photocoagulation

• Solitary Solid Benign “Cold” Thyroid Nodules – mean thyroid nodule volumes decreased by 40%

to 50% after 6 months, – improvement of local clinical symptoms in

approximately 80% of patients and no side effects.

Reliability of Thyroid Imaging Reporting and Data System (TIRADS) Classification in Differentiating

Benign from Malignant Thyroid Nodules*

Open Journal of Radiology, 2013, 3, 103-107

Parathyroid Imaging

Anatomy• Derived from the third (lower

parathyroid glands) and fourth (upper parathyroid glands) pharyngeal pouches.

• 25% of individuals have more than 4 glands.

• May be aberrantly located anywhere from the carotid bifurcation to the anterior mediastinum.

• Two dominant cell types:– the chief cells - source of

parathormone.– the oxyphil cells

• Vascular supply– superior and inferior thyroidal arteries,– venous drainage to thyroidal veins.

• Nerve Supply:– innervated through the cervical sympathetic

plexus.

Imaging

Scinitigraphy

• The agents for scintigraphic localization of parathyroid adenomas include: – thallium (Tl)-201 Technetium (Tc)-99m

pertechnetate subtraction scanning,– 99mTc-sestamibi (hexakis-2-methoxy-

isobutylisonitrile) subtraction imaging with iodine-123 (I-123) or 99mTc pertechnetate, and

– 99mTc-sestamibi imaging without subtraction.

Hyperparathyroidism

• Classic findings of stones (renal calculi), groans (abdominal pain), bones (demineralization or arthritis), or moans (psychiatric disturbances).

Parathyroid in Primary Hyperparathyroidism

• Single adenoma – 80 – 85%• Hyperplasia – 12 – 15% • Multiple gland disease – 2 – 3%• Carcinoma – < 2%

• Aetiology– Sporadic– Prior external neck irradiation– Long term lithium therapy– MEN 1, 2A– Familial hypocalciuric hypercalcemia– Parathyroid carcinoma

Parathyroid Adenoma

Imaging - USG

• Typically not visualized– Small size– Increased gland fat

• Of those glands greater than 1 g in size, ultrasonography had a detection rate of 95%.

Gray Scale Features of Parathyroid Adenomas

• Shape – Typically oval or bean shaped– Asymmetrical enlargement– Teardrop or bilobed shape

• Echogenicity– Hypoechoic

• Uniform hypercellularity of the gland

• Lipoadenomas are more echogenic (due to high fat content)

– Homogenously solid• 2% cystic degeneration

Vascularity

• Enlarged Extrathyroidal Feeding Artery– Highly vascular lesions

supplied by enlarged feeding arteries that usually arise from branches of the inferior thyroidal artery

Vascularity

• Polar Vascularity– feeding arteries of

parathyroid adenomas characteristically supply the adenoma at the pole of its long axis.

Vascularity

• Peripheral Vascular Pattern

• As the feeding artery enters the adenoma, it arborizes around the periphery before smaller branches penetrate deeper exhibited a well-defined vascular “arc” or “rim.”

Vascularity• Vascular Asymmetry of the

Thyroid Gland• The hypervascular adenomas

and their associated feeding vessels may result in increased unilateral flow within the thyroid tissue adjacent to an adenoma.

• This diffuse increase in vascularity was distinct from the feeding artery described above and provided a helpful indirect clue for locating adenomas.

Left

Right

Graded Compression

Transverse images without (A) and with (B) compression, which improves visualization of the adenoma. The relationship between this deep adenoma and the longus colli muscle is also demonstrated

Graded Compression

Transverse images without (A) and with (B) compression, showing dramatic improvement of visualization of a very small adenoma.

Potential Pitfalls

False Positives• Cervical lymph node• Prominent blood vessel• Esophagus• Longus coli muscle• Thyroid nodule

False negatives• Minimally enlarged

adenoma/gland• Multinodular thyroid goiter• Ectopic parathyroid adenoma

Cervical lymph node

Although the gray scale image shows a lesion that is indistinguishable from a parathyroid adenoma, the color Doppler image shows central hilar vascularity. This node proved to contain metastatic thyroid adenocarcinoma.

Parathyroid Adenoma vs Cervical lymph node

The primary artery to the adenoma ends bluntly in its parenchyma

Doppler imaging of a hyperplastic lymph nodedemonstrates a pattern of internal arborization within the lymph node

• Sonographic localisation of parathyroid adenoma localisation – Sensitivity 74 – 89%– Accuracy 74 – 94%

• USG augmented by FNA Biopsy and PTH assay – Specificity 100%– Sensitivity 90%– Accuracy 82%

Intraoperative Sonography

• Particularly in the reoperative setting• Sterile high frequency (8 – 15Hz)• Localizing abnormal inferior and intrathyroid

parathyroid glands• Adv:

– Focused surgical resection to limit tissue damage– Directed resection of ectopic adenomas in the

mediastinum, thyroid and carotid sheath– Surgical time may be shortened.

Other modalities

• Combined imaging with ultrasound and 99mTc sestamibi scintigraphy for preoperative diagnosis of parathyroid disease.

• MRI combined with 99mTc sestamibi scintigraphy increased imaging sensitivity in evaluation of recurrent or resistent hyperparathyroidism

CT scan demonstrates a small mass adjacent to the left pyriform sinus (a). The submandibular gland is defined (b)

MRI scan confirms the findings on previousCT scan. The undescended parathyroid gland/adenoma is demonstrated ( a ), as is the opposite submandibular gland ( b )

This patient was evaluated after a failed parathyroid exploration. Sestamibi scan was interpreted as negative, and no preoperative ultrasound was performed in this early case.

Parathyroid Hyperplasia

• Approximately 30% of patients with parathyroid hyperplasia have familial hyperparathyroidism, including variants of the multiple endocrine neoplasia (MEN) syndromes.

• Sensitivity rate for detecting hyperplastic glands of:– CT 45% - 88%– USG 30% - 69%– MRI 40% - 63% – thallium subtraction 43% - 65%– 99mTc sestamibi 55% - 75%

Parathyroid Carcinoma• Of all patients with hyperparathyroidism, the incidence of parathyroid

carcinoma is only 1% to 2%, • Although parathyroid carcinoma causes hyperparathyroidism in 85% to

90% of cases.• Metastases to lymph nodes occur in one third of cases, and distant

metastases in27% to28% of patients.• Men and women are affected equally.• Edmonson and colleagues noted that a parathyroid carcinoma may have

the same sonographic appearance as a benign large adenoma (hypoechoic with or without heterogeneity);

• Only the presence of local invasion into the thyroid gland, muscles or vessels, or nodal metastases would suggest this diagnosis.

• Parathyroid carcinomas have been reported to accumulate 99mTc sestamibi.

Parathyroid carcinoma does not usually demonstratespecific features on ultrasound. This transverseimage (a) is rather nonspecific.

Representative histologyis presented from this same patient’s mass (b,c), and the confirmed diagnosis is that of a parathyroid carcinoma.

Often, this may be suspected based on extremely high calciumlevels or surgical findings of adherence and invasionrather than any imaging parameter

Secondary and Tertiary Hyperparathyroidism

• The evaluation of patients with secondary or tertiary hyperparathyroidism is rarely centered around the parathyroid glands because the kidneys are the source of abnormality in these diseases.

• Parathyroid glandular hyperplasia usually occurs in association with chronic renal failure and renal osteodystrophy.

• 99m-Tc sestamibi has been able to identify bilateral uptake in hyperplastic glands and residual parathyroid tissue in those individuals treated surgically in the neck for secondary hyperparathyroidism.

The parathyroid glands in secondary hyperparathyroidism can be quite large and rounded

Percutaneous Biopsy

• Particularly in candidates for reoperation• Decrease the false positives• Increase the specificity• Reassure the reluctant patient• Diagnostic confirmation before percutaneously injected ethanol

ablation• Aspirate ----- cytology & PTH assay• Compl:

– Post biopsy periglandular fibrosis– Parathymosis

• Implantation of hyperfunctioning parathyroid tissue in neck or mediastinum, resulting in hypercalcemia

Ethanol Ablation - Who?

• Postoperative patients with recurrent or persistent hyperparathyroidism who have sonographically visible, biopsy proven hyperfunctioning parathyroid tissue, but who are poor surgical candidates.

• Dialysis patients with secondary hyperparathyroidism• Patients with h/o multigland disease with recalcitrant

recurrent hyperparathyroidism after subtotal surgery• Patients with MEN 1 who have had previous subtotal subtotal

parathyroidectomy and recurrent disease in the residual gland• Recurrent graft dependent hyperparathyroidism• Tertiary hyperparathyroidism

Ethanol Ablation - Procedure

• Sterile 95% ethanol• Multiple regions of the mass• Volume half that of the mass (0.1 to 1.0 mL)• Immediately echogenic – slowly disappears

over 1 minute• Repeated • Long term close follow up

Ethanol Ablation - Adverse Effects

• Temporary jaw pain• Dysphonia - transient

Ethanol Ablation - Disadvantages

• Long term efficacy < surgical• Postablation periglandular fibrosis

• Reasons for failure:– Incomplete ablation of the hyperfunctioning tissue

of treated adenoma– Residual hyperfunctioning of other untreated

glands in the patient with unrecognized multigland disease.

Parathyroid Cysts• lower neck in the paramedian

position• more common in women than in

men and • may be present in the neck or

anterior mediastinum. • At presentation, they may be very

large in size, and the differential diagnosis may include thyroid cysts, thymic cysts, and necrotic lymph nodes.

• They usually arise in the region of the inferior pole of the thyroid gland.

• They are virtually never found in children; most cases present in the fourth and fifth decade of life.

• Ultrasound displays a thin-walled cyst below but immediately adjacent to the thyroid gland.

• The cysts demonstrate typical posterior enhancement.

• The parathyroid cyst is noted to be separate from the thyroid gland.

• In contradistinction, a large parathyroid adenoma may undergo complete or partial cystic degeneration, but there is usually a solid component, and the patient has typical laboratory confirmation of the hyperparathyroid state.

• The clue to the proper diagnosis of parathyroid cyst is retrieval of clear fluid on aspiration and identification of a high intact PTH value.

• They are usually unilocular, large, and may have hyperproteinaceous contents yielding high intensity on Tl-weighted MR scans.

Hypoparathyroidism• The most common cause of hypoparathyroidism is iatrogenic removal of

all functioning parathyroid tissue during surgery for hyperparathyroidism or thyroid disease.

• Primary idiopathic hypoparathyroidism is a disease of childhood unassociated with cervical abnormalities.

• Pseudohypoparathyroidism may be caused by renal disease; the serum parathormone (PTH) levels are paradoxically high because of a lack of renal responsiveness to the hormone.

• In pseudopseudohypoparathyroidism, the calcium and phosphate levels are normal, although the physical features of pseudohypoparathyroidism (coarse facies, dwarfism, mental retardation, round face, stubby fingers) may be present.

• The glands may be normal or hyperplastic.

• Imaging of parathyroid glands in patients with hypoparathyroidism is limited to the surveillance for congenital absence, which is best accomplished with scintigraphic methods

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Health & Medicine

Thyroid & parathyroid