The thyroid gland is located in the neck and produces hormones that regulate metabolism. It can be imaged using ultrasound, radioactive iodine scans, or technetium scans. Ultrasound is often used to evaluate thyroid nodules for signs of malignancy such as microcalcifications or irregular margins. Radioactive iodine uptake tests measure how much radioiodine is absorbed by the thyroid and can help distinguish hyperthyroidism from hypothyroidism. Diseases like Graves' disease, Hashimoto's thyroiditis, thyroid cancer and nodules can be identified and monitored using thyroid imaging techniques.

1. THYROID IMAGING
BWAMBALE JIMMY

2. • Anatomy and physiology
• Embryology
• Normal variations
• Hypothyroidism
• Hyperthyroidism
• Thyroid nodules

3. • The thyroid gland is a highly vascularized bi-lobed endocrine gland
situated in the median anterior neck inferior to the laryngeal thyroid
cartilage typically corresponding to vertebral bodies C5-T1. The two
lobes are connected anteriorly by the isthmus to produce a butterfly
appearance. It weighs about 10-25grams.
• The lobes are wrapped around the cricoid cartilage and superior rings
of the trachea and are bound by the pre-tracheal fascia. The thyroid
gland attaches to the trachea via a consolidation of connective tissue
called the lateral suspensory ligament or berry’s ligament.
• Embedded posterior to each thyroid lobe is a parathyroid gland.

4. Anatomy
TeachMeSeries Ltd (2021

5. Anatomical relations
• Anteriorly: infrahoid muscles,sternohyoid,superior belly of the
omohyoid and stern thyroid
• Laterally carotid sheath; containing the common carotid artery,
internal jugular vein and vagus nerve.
• Medially:larynx,pharnx,trachea and esophagus.

9. Blood supply
Arterial blood supply is by two arteries;
• Superior thyroid artery, the first branch of the external carotid artery.
• Inferior thyroid artery a branch of the subclavian artery.
• In 10% of the population, The thyroid ima artery that arises from the
brachiocephalic trunk supplies the anterior surface and the isthmus
of the thyroid gland.
Venous drainage
• The thyroid gland drains via the superior, middle and inferior thyroid
veins which form a venous plexus.
• The superior and middle veins later drain into the internal jugular
vein and the inferior into the brachiocephalic vein

11. • Innervation
• The parasympathetic fibers that innervate the thyroid gland originate
from the vagus nerve while the sympathetic fibers originate from the
inferior, middle and superior ganglia of the sympathetic trunk.
• Release of thyroid hormone is controlled by the pituitary gland.

13. • Lymphatic drainage
It drains in to the paratracheal and
the deep cervical nodes.

14. Embryology

15. • It’s the first endocrine gland to develop
• Embryology begins on the 24th day of gestation
• Originates from primitive pharynx and the neural tube
• Lateral thyroid develops from the neural crest cells and the medial
thyroid develops from the primitive pharynx.
• Endothelial epithelial cells proliferate on the developing pharyngeal
floor between the 1st and 2nd pharyngeal arches.
• These proliferating cells(thyroid primodium) develops to form the
thyroid diverticulum

16. • The thyroid diverticulum is initially hollow but later solidifies and
becomes bilobed. The thyroid stem usually has a lumen (thyroglossal
duct that does not descend into the lateral lobes.)
• The two lobes are connected by an isthmus

17. Thyroid descent
• Initial thyroid descend follows the primitive heart and it
occurs anterior to the pharyngeal gut.
• At this point it’s still connected to the tongue by the
thyroglossal duct
• The proximal segment of the duct retracts and obliterates,
leaving only the foramen cecum
• The inferior end of the duct also obliterates. Failure of
obliteration of the inferior end leads to formation of the
pyramidal thyroid lobe.
• As it descends, it forms a mature shape and by the 7TH
gestation week, it comes to rest in its orthotopic position.

19. Clinical correlation of thyroid embryology
• If the thyroglossal duct does not atrophy, the remnant manifests
clinically as a thyroglossal duct cyst. The cyst is often located below
the level of the hyoid bone but may track anywhere along the
embryonic course of descent. rupture of this cyst may cause a
thyroglossal duct sinus.

21. Failure of the thyroid to descend leads to ectopic thyroid tissue.
Ectopic thyroid tissue may occur anywhere along the course of descent
although its commonest at the base of the tongue where it’s called
lingual thyroid. Ectopic thyroid may be associated with hypothyroidism

23. Ectopic thyroid tissue

25. Accessory thyroid tissue may also occur from remnant of the
thyroglossal duct. They appear anywhere along the course of descend
of the thyroglossal duct.

26. A pyramidal lobe arises when the inferior end of the thyroglossal duct
fails to obliterate. Its usually attached to the superior edge of the
isthmus, more common on the left.

27. Pyramidal lobe

28. Thyroid hemi agenesis

29. Agenesis
Failure of one lobe to develop
especially the left is found
incidentally.
Patients present with hypothyroid
manifesting in early childhood as
cretinism(physical deformity and
learning difficulty)

30. physiology

31. Thyroid hormone synthesis

34. T3 and T4
• T4 is a prohormone while T3 is the active hormone.
• T4 undergoes monodeiodination(in extra thyroid tissues) to form T3

35. Functions of the thyroid gland
• The thyroid maintains normal body metabolism , physical and mental
growthand development by the synthesis, storage, and secretion of
thyroid hormones T3 AND T4

36. Anti thyroid drugs
• Influence synthesis, release and peripheral metabolism of thyroid
hormones and are thus used in treatment of hyperthyroidism.
• Methiamazole,glucocorticoids,lithium.

37. hypothyroidism
• Is the most common thyroid disorder. In adults it’s referred to as
myxedema
• 75% of hypothyroidism is caused by a chronic thyroid inflammatory
process called Hashimoto’s thyroiditis which may be a sequel to an
autoimmune response.
• However ,it may also occur as a result to malfunction of the pituitary
gland
• Other causes of hypothyroidism include medications, radiation
exposure,edemic iodine deficiency,hyperfunctioning thyroid cancer
neonatal thyrotoxicosis(maternal graves disease) among others.

38. Clinical signs and symptoms
weight gain,
hair loss
increased subcutaneous tissue around the eyes
lethargy,
intellectual and motor slowing,
cold intolerance
constipation
and a deep husky voice.

39. Hyperthyroidism
• Iodine excess may lead to over
production of thyroid hormone a
condition termed “jodbasedow”
• The gland has impaired function
and demonstrates diffuse
enlargement.
May be stimulated by,
• Grave’s disease
• Toxic multinodular goiter
• Toxic adenoma
• Acute or sub acute thyroiditis
• Hyper functioning thyroid cancer
• Choriocarcinoma or hydatidiform
mole
• Thyroid-stimulating hormone–
secreting pituitary adenoma
• Amiadorone (antiarthmic drug)

40. Clinical signs and symptoms
• Adrenergic- palpitations,anxiety,hyperdefecation,heat/cold
intolerance.
• Cardiovascular-Tachycardia, dyspnea, orthopnea and peripheral
edema.
• metabolism,-weight loss
• Neuromuscular-Brisk peripheral reflexes, weakness of proximal
muscles
• Neuropsyciatric- Insomnia,rapid and pressured speech

41. IMAGING MODALITIES
• Ultrasound
• Plain X-ray (In patients with MNG to rule out pressure effect on the
trachea and retrosternal extension)
• MRI (Not routine)
• Scintigraphy

42. Indications for thyroid imaging
• Differential diagnosis of hyperthyroidism
• Suspected thyroid cancer
• Suspected metastasis of thyroid cancer
• Thyroid nodule
• Thyroid inflammation
• Determine the efficacy of radioactive iodine therapy
• Organification (incorporation of iodine into thyroglobulin) defects
• Determine congenital thyroid defects

43. Thyroiditis
An acute thyroid destructive
process.
Can be autoimmune, infectious or
drug related such as in post
partum, viral and Amiodarone
induced thyroiditis respectively.
Cell membrane breaks down and
releases excessive amounts of
thyroid hormone into the
circulation
In Some patient’s a normal thyroid
state may be auto restored in 2-4
months and others may develop
permanent hypothyroidism.

44. Post partum thyroiditis
• Pregnancy and stress are
associated with immune
suppression, and subsequent
release from suppression may
lead to heightened immune
activity precipitating a thyroid
disorder
Occurs in 1-17% of women with
preexisting subclinical
autoimmune thyroid disease.

45. Post partum thyroiditis
• Commonly occurs in women
with elevated thyroid peroxidase
in early pregnancy.
• Has a strong association with
diabetes mellitus and it tends to
reoccur during subsequent
pregnancies.
• Characterized by initial
hyperthyroidism, followed by
hypothyroidism(due to deletion
of the thyroid stores) and then
Euthyroidisim(normal state)
• Extreme fatigue and postpartum
depression and suicide have
been linked to the disorder.

46. Viral thyroiditis
• Usually follows an upper
respiratory tract infection
• Clinically it presents as a painful
and tender goiter with
associated general malaise and
fever.
• TFT’s are elevated in the acute
phase and gradually return to
Euthyroid levels in 2-4 months

47. Amiodarone induced thyroiditis
• Iodine rich benzofuran derivative
used to treat and prevent
cardiac arrhythmias.
• Has a long half life(3-4months)
and is stored in fat
• Induces hyperthyroidism due to
increased hormone sythesisis
• Amiodarone induced
hypothyroidism is believed to
result from the inability of the
thyroid to escape from the
Wolff-Chaikoff effect.
• Thyroid hormone biosynthesis is
impaired because of the
persistent block in intrathyroidal
iodine organification

48. thyroiditis

50. Autoimmune thyroid diseases

51. Hashimoto’s disease
• Chronic autoimmune thyroid
disease also known as chronic
lymphocytic thyroiditis.
• More common in women with a
20%incidence in iodine replete
areas where it’s the most
common cause of goiter and
hypothyroidism.
• Associated with auto
sensitization of thyroid
peroxidase and thyroglobulin

52. Radiographic findings
• Diffusely enlarged gland with
heterogeneous echo texture
• Hypoechoic micro(1-6mm)nodules
• Hyper/normal vascularity on
Doppler
• Reactive cervical lymnodes may be
present

55. Grave’s disease
• Autoimmune thyroid disease that results from an antibody directed
stimulation of the thyroid-stimulating hormone (TSH) receptor, with
resultant production and release of T3 and T4.
• Occurs in genetically susceptible persons and is more common in
women
• Clinical features, fatigue ,change in bowel habits,restlessness, anxiety,
irritability, insomnia etc.
• Associated with optalmopathy

57. Ultrasonographic features of Grave’s disease
• Hyper vascularity
• Diffuse coarse thyroid echo
texture
• Diffuse gland enlargement

60. Thyroid neoplasm
Findings indicative of malignancy
• Micro-calcifications
• Irregular/microlobular margins
• Hypo echogenicity
• Taller than wide shape
• Increased intranodular vascularity

61. Features indicative of benignancy
• Cystic lesions
• Iso/hyper echoic well
circumscribed lesions

62. US image of a thyroid nodule (arrowheads) containing multiple fine punctuate echogenicity's
(arrow) with no comet-tail artifact, indicating high suspicion for malignancy. FNA and surgery confirmed PTC. (Reproduced from Frates MC.
Management of thyroid nodules detected at US: Society of Radiologists in Ultrasound consensus conference statement. Radiology2005;237:794–800;
with permission.)

63. Malignant thyroid nodules

64. US image of a cystic thyroid nodule (arrowheads). (Reproduced from Frates MC.
Management of thyroid nodules detected at US: Society of Radiologists in Ultrasound consensus conference statement.
Radiology 2005;237:794–800; with permission.)

68. Thyroid adenoma

69. Thyroid adenoma

70. multinodular goitre

74. Endemic goiter
• Attributed to iodine deficiency
or goitrogens which are present
in Some foods.
• cassava,cabbages,turnip,brocho
oli contain cynoglucosides
• cyanoglucosides can be
metabolized to thiocynate.
Thiocynate interferes with iodine
trapping and organification leading to
inefficient hormone synthesis which
leads to compensatory increase in
TSH.

76. N.B ultrasonography/Imaging has high
sensitivity but low specificity in the
differentiation of thyroid autoimmune and
inflammatory processes, thus Clinical and
laboratory correlation are invaluable for
definitive diagnosis

77. TIRADS

78. Thyroid scintigraphy
• Routinely used for the diagnosis
of and management of thyroid
conditions

79. Radio-nuclides
• I-123 ;Most commonly used
because of its excellent image
quality and low radiation dose.
• I-131;Used for therapeutic
purposes because of its beta
emission and high radiation dose
• 𝑇99𝑚 pertechnetate
• Used as a substitute for iodine because
its trapped by iodine, readily available,
inexpensive ,low radiation dose.

80. I-123
• Biochemical behavior is identical to
that of stable iodine and is thus
absorbed into the body in the GIT.
• Trapped by thyroid follicular cells and
incorporated into thyroglobulin
• Decays by electron capture with a half
life of 13hours and a photon energy of
159Kev.
• The gamma emission allows for
excellent imaging with low
background activity providing low
radiation to the thyroid
• Dose and route I: 200-400 μCi (7.4-
14.8 MBq) p.o.

81. Iodine-131
• Decays by beta emission.
• T1/2 8.04days
• Long half life and high beta
emission cause relatively high
radiation dose making it
undesirable for routine imaging
of the thyroid.
• Used in scanning for metastatic
carcinoma since scanning can be
done over several days
Not used for imaging in benign
disease due to beta
emissions/high radiation dose to
thyroid (1 rad/μCi)

82. Tc-99m pertechnetate
• Not organified into the thyroid
follicular cells but released over time
as unaltered pertechnetate ion.
• Only 1-5% of administered 99tc04- is
trapped by the thyroid so images
background levels are higher than
with radio-iodine.
• Dose:2-10 mCi (74-370 MBq) IV
• Preferred over radioiodine when a
patient has been receiving thyroid
blocking agents such as iodinated
contrast agents

83. Iodine uptake test
• Performed before the
radioiodine therapy to ensure
that the thyroid will take up
iodine and determines how
much.
• Can be used to differentiate
between graves disease and sub
acute
thyroiditis.
• A gamma probe is placed over
the thyroid gland to measure the
amount of radioactivity of the
thyroid gland.
• This amount of radioactivity is
compared with the original dose
of radioactivity and is reported
as a percentage.

84. Significance of iodine uptake test
Normal range:6hour 3-16%
24hours 8-25%
Increased radioactivity >35% after
24hours
Hyperthyroidism
Hashimotos thyroiditis(early)
Goiter
Decreased radioactivity
• hypothyroidism
• subacute thyroiditis
• iodine overload (excessive iodine
ingestion)

85. >35% after 24hours
Hyperthyroidism
Hasmimotos thyroiditis
goiter
Decreased radioactivity
Hypothyroidism
Sub acute thyroiditis
Excessive iodine intake
Normal range
3-16% after 3hours
8-25% after 24hours

86. Factors affecting iodine uptake
Increased uptake
• Hyperthyroidism
• Hashimotos thyroiditis.
• Iodine starvation
• Pregnancy
• Enzyme defects
• TSH
Decreased uptake
• Hypothyroidism
• Iodine overload i.e. from
iodinated contrast media
• Iodine containing medications
• Thyroid hormone therapy
• Ectopic secretion of thyroid
hormone
• Renal failure

87. Indications for thyroid scintigraphy
• To differentiate causes of primary hyperthyroidism
• To locate ectopic thyroid tissue.
• To assist in evaluation of congenital hypothyroidism/ organification defects.
• To determine that a cervical/mediastinal mass is thyroid tissue.
• To evaluate functionality of a nodule/s
N.B contraindicated in breast feeding mother and pregnant women. ?risk
benefit assessment.

88. What are the prerequisites?
• Previous investigations confirming thyroid pathology by either: abnormal
thyroid function tests or ultrasound study.
• Ensuring that no previous radiological procedure requiring the injection of
iodine contrast medium has been carried out 8 weeks before the thyroid
scan.
• Ensuring cessation of iodine-containing foods, vitamin supplements and
medicines before the scan for a minimum of 1–2 weeks.
• Ensuring cessation of the following drugs before the scan:
• Thyroxine (at least 1 week);
• Liothyronine – needs to be ceased for 5 days
• Amiodarone – 3 months before the scan
• Lithium ,carbimazole,propylthiaouracil

89. Technique and clinical protocol
Technetium-99m
• Image is taken 20 minutes after
5 to10 mCi (185-370MBq) IV
injection.
• With Patient supine, neck
extended Anterior ,left and right
oblique images are then
obtained for 100,000 to 300,000
counts or 5 minutes acqusitition.

90. Technique -Iodine 123
• Image is taken 3-4hours and after oral
administration of 200 to 600µCi to a fasting patient.
• 50,000-100,000 count/10minute acquisition.
• Imaging 16-24 hours may give more accurate detail
of the distribution of organified iodine that earlier
images.

91. Normal images
• Bi-lobed thyroid with
homogenous distribution of
activity.
• In a small number of patients, a
pyramidal lobe may be
indemnified.

92. Pyramidal lobe

93. • Ectopic thyroid tissue
• May occur in base of the
tongue(lingual
goitre,retrosteranally(sub sternal
goiter),pelvis(struma ovarii)

94. Ectopic?

95. A radioiodine stan shows the left thyroid lobe extending inferiorly in a substernal goiter.

96. Congenital organification defect
• A 24 hour radioiodine scan
shows no activity.
• A 2 to 4 hour Technetium 99
pertechnetate shows activity
because the trapping
mechanism of the gland is intact

97. Grave’s Disease
• Varying degrees of
thyromegaly with
uniform
distribution of
increased activity.

98. Graves disease

99. Thyroid nodules
• Cold nodules demonstrate
absence of activity(cysts)
• Hot nodules are identified by
focally increased activity
compared to normal thyroid
parenchyma.
• Nodules that are neither hot nor
cold are called warm nodules.

105. Multi nodular goiter
• Enlarged gland with
multiple cold, warm or
hot areas giving the
gland a coarse patchy
appearance.

106. Discordant nodules
• A small number of
hot nodules on
technetium
peretechnetate have
proved to be cold on
iodine imaging.

107. Thyroiditis
• Early-Diffusely uniform
increased activity in the
gland(which may resemble
Grave’s disease)

108. Late(chronic thyroiditis)-
Coarsely patchy distribution of
activity(which may mimic
MNG)

109. Post thyroidectomy imaging
• A whole body imaging device or a large field of view gamma camera is
used.
• Activity is commonly seen in the stomach, bowel and bladder.
• Mild activity is also seen in the liver due to clearance of bound iodine
by the liver.
• A star artifact is commonly seen when remnamt residual thyroid
tissue accumulates a lot of radioiodine some of wihc escapes the lead
septa in a star pattern.

112. Post radioiodine therapy imaging
• Whole body imaging at 6 months to 1 year interval.
• Thyroid hormone withdrawal for 4-6 weeks
• Subsequent identification of functioning tissue in the neck should be
treated as tumor recurrence.

113. Thank you for listening
• Ilahi A, Muco E, Ilahi TB. StatPearls [Internet]. StatPearls Publishing;
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• May 14, 2017 | Posted by admin in HEAD & NECK IMAGING |
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fication_in_Differentiating_Benign_from_Malignant_Thyroid_Nodules
• Diagnostic Radiology Essentials.A.Adam,R.G.Grainger.D.J.Allison