1. Thyroid disease By
Dr Fahad

2. Anatomy of the Thyroid Gland

3. Location: ant neck at C5-T1, overlays 2nd – 4th tracheal rings
Average width: mm (each lobe)
Average height: mm long

4. Thyroid Diseases
Thyrotoxicosis
Hypothyroidism
Thyroid nodules

5. Thyrotoxicosis VS Hyperthyroidism
Thyrotoxicosis: a group of symptoms and signs due to elevated thyroid hormones in the body of any cause.
Hyperthyroidism: a group of symptoms and signs due to increased production of thyroid hormones by hyper functioning thyroid gland.

6. Causes of Thyrotoxicosis
Hyperthyroidism
1- Diffuse toxic goiter (Graves’ disease)
2- Single toxic nodule
3- Toxic multi-nodular goiter
Early phase sub-acute thyroiditis
Exogenous thyroid hormone intake

7. Thyroiditis and exogenous thyroid hormone intake
Early phase sub-acute thyroiditis: inflammation of thyroid gland that leads to release of stored thyroid hormone due to follicular cell destruction. In acute stage, the patient is thyrotoxic.
Exogenous thyroid hormone intake:
1- By mistake
2- with weight loss pills

8. Thyrotoxicosis and TFT
TSH is always suppressed in thyrotoxicosis.
TSH is the most sensitive test for thyroid function and it is the screening test for thyroid dysfunction.
If TSH is abnormal, T3 and T4 levels can be obtained in order to determine the severity of the disease. T3 and T4 are usually elevated in thyrotoxicosis.

9. TFT and Thyroid scan
Thyrotoxicosis= suppressed TSH and elevated T3/T4.
Based on TFT, the exact cause of thyrotoxicosis can not be determined.
Thyroid scan is a very helpful tool in differentiating between various causes of thyrotoxicosis.

10. Thyroid scan and uptake
Radioactive Iodine (RAI) is used for thyroid scan and uptake.
RAI is given orally.
Image and uptake are obtained after 24 hours
Follicular cell traps Iodine and organifys it to be incorporated with thyroid hormone.

11. Imaging findings Symmetric or asymmetric lobes.
Homogeneous or inhomogeneous uptake
Nodules; cold or hot

12. 24-hour RAI uptake
Measure photons in the given RAI by a special probe (uptake probe) just before taking RAI.
After 24 hours, measure photons in the neck (thyroid gland).
Calculate % of photons concentrated in thyroid gland.
Normal range of 24 RAI uptake is 10%- 30%

13. Thyroid Uptake Probe

15. Increase uptake Hyperthyroidism Iodine starvation Thyroiditis
Hypoalbominemia
lithium

16. decrease uptake Hypothyroidism
Thyroid hormon therapy, PTU ,Lugol’s solution
Medication(contrast , multivitamins )
Thyroiditis

17. Diffuse Toxic goiter (Graves’ Disease)
Diffuse enlargement of thyroid gland.
Homogeneous uptake.
No significant focal abnormalities (nodules).
24-hour RAI uptake is elevated, usually > 35% (mean of 40%).

18. Graves’ Disease autoimmune disorder
presence of circulating antibodies directed at TSH receptors; stimulate the receptors
excessive thyroid hormone leads to hyperthyroidism
If you have Graves' disease, you may experience one or more of the following symptoms:
Nervousness; Irritability; Difficulty sleeping ; Rapid heartbeat ; Fine tremor of the hands or fingers ; Increased sweating ; Sensitivity to heat ; Sudden weight loss ; Bulging eyes ; Unblinking stare ; Goiter ; light menstrual periods ; Frequent bowel movements
unrelated tissue manifestations such as exophthalmos
In Graves' ophthalmopathy, the eyeball protrudes beyond its protective orbit (see graphic below) because tissues behind the eye attract and hold water. When this happens, the tissues and muscles swell, causing the eyeball to move forward in the orbit. The front surface of the eye can dry out. Eye symptoms and hyperthyroidism symptoms usually appear within 18 months of each other.
sometimes referred to as diffuse toxic goiter

19. Single Toxic Nodule
Single hot nodule (independent of TSH or autonomous).
Rest of thyroid gland is poorly visualized due to low TSH level (TSH dependant).
24-hour RAI uptake is slightly elevated, usually around 20%.

20. Toxic Nodule

21. Hot Nodule

22. Toxic Multi-Nodular Goiter
Mild inhomogeneous uptake in thyroid gland.
Multiple cold and hot nodules in both thyroid lobes.
24-hour uptake is mildly elevated, usually between 20%-30%.

23. Multi-nodular Goiter
• Cut surface of one lobe of thyroid gland showing ill defined nodules. • Focus of cystic degeneration seen (blue arrow). • Some hemorrhage (red arrow) and some scarring.

24. Multi-nodular Goiter

25. Early Phase Sub-acute Thyroiditis
Inhomogeneous uptake could be mild or severe. In some cases thyroid gland is not visualized.
No significant focal abnormalities (nodules).
24-hour RAI uptake is low, usually < 5%.

26. Sub-acute Thyroiditis

28. Hypothyroidism
The main cause is chronic thyroiditis (Hashimoto’s thyroiditis).
TSH is elevated.
Thyroid scan does not have significant diagnostic value in this entity.
However, if there is nodule/nodules confirmed by physical examination and ultrasound, thyroid scan may be helpful.

29. Thyroid Nodules
thyroid nodules are common, perhaps existing in almost half the population
Nodules are usually found by physical examination or by ultrasound.
US is the first modality used to investigate a palpable thyroid nodule 
scintigraphy is reserved for characterizing functioning nodules and for staging follicular and papillary carcinomas.
The patient is usually euthyroid.

30. If the patient is hyperthyroid do nuclear scan otherwise do FNA.
FNA is the most accurate and cost- effective method for diagnostic evaluation of thyroid nodules.
FNA have a sensitivity of 76%–98%, specificity of 71%–100%

31. Frequency of Occurrence of Thyroid Malignancies

32. Risk factors for thyroid cancer
family history of thyroid cancer,
a history of head and neck irradiation,
male sex,
age of less than 30 years or more than 60 years,
previous diagnosis of type 2 multiple endocrine neoplasia

33. US features of thyroid nodules
there is some overlap between the US appearance of benign nodules and that of malignant nodules
certain US features are helpful in differentiating between the two. These features include
micro-calcifications
local invasion
lymph node metastases
a nodule that is taller than it is wide
markedly reduced echogenicity.
Other features, such as the absence of a halo, ill- defined irregular margins, solid composition, and vascularity, are less specific but may be useful.

34. US Features Associated with Thyroid Cancer

35. Thyroid microcalcifications
They are psammoma bodies, which are 10–100-μm round laminar crystalline calcific deposits. They are one of the most specific features of thyroid malignancy, with a specificity of 85.8%–95% and a positive predictive value of 41.8%–94.2%

36. Figure 2a. Papillary thyroid carcinoma in a 42-year-old man.
Figure 2a.  Papillary thyroid carcinoma in a 42-year-old man. (a) Photomicrograph (original magnification, × 400; hematoxylineosin stain) shows a psammoma body (arrow), a round laminar crystalline calcification. (b) Transverse sonogram of the right lobe of the thyroid demonstrates punctate echogenic foci without posterior acoustic shadowing, findings indicative of microcalcifications (arrows).
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

37. Figure 2b. Papillary thyroid carcinoma in a 42-year-old man.
Figure 2b.  Papillary thyroid carcinoma in a 42-year-old man. (a) Photomicrograph (original magnification, × 400; hematoxylineosin stain) shows a psammoma body (arrow), a round laminar crystalline calcification. (b) Transverse sonogram of the right lobe of the thyroid demonstrates punctate echogenic foci without posterior acoustic shadowing, findings indicative of microcalcifications (arrows).
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

38. Local Invasion and Lymph Node Metastases
US features that should arouse suspicion about lymph node metastases include a rounded bulging shape, increased size, replaced fatty hilum, irregular margins, heterogeneous echotexture, calcifications, cystic areas and vascularity throughout the lymph node instead of normal central hilar vessels at Doppler imaging 

39. Figure 5a. Anaplastic thyroid carcinoma in an 84-year-old woman.
Figure 5a.  Anaplastic thyroid carcinoma in an 84-year-old woman. (a) Transverse sonogram of the left lobe of the thyroid shows an advanced tumor with infiltrative posterior margins (arrows) and invasion of prevertebral muscle. (b) Axial contrast-enhanced CT image shows a large tumor that has invaded the prevertebral muscle (arrows).
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

40. Figure 5b. Anaplastic thyroid carcinoma in an 84-year-old woman.
Figure 5b.  Anaplastic thyroid carcinoma in an 84-year-old woman. (a) Transverse sonogram of the left lobe of the thyroid shows an advanced tumor with infiltrative posterior margins (arrows) and invasion of prevertebral muscle. (b) Axial contrast-enhanced CT image shows a large tumor that has invaded the prevertebral muscle (arrows).
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

41. Figure 7b.  Papillary carcinoma and cystic lymph node metastasis in a 28-year-old woman.
Figure 7b.  Papillary carcinoma and cystic lymph node metastasis in a 28-year-old woman. (a) Longitudinal sonogram of the right lobe of the thyroid shows an irregular hypoechoic tumor with microcalcifications. (b) Longitudinal sonogram of the right neck shows a cystic level 5 nodal metastasis with internal septation and foci of calcification (arrows). (c) Axial contrast-enhanced CT image shows the metastasis (arrow).
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

42. Margins, Contour, and Shape
A completely uniform halo around a nodule is highly suggestive of benignity, with a specificity of 95% 

43. Figure 9. Follicular adenoma in a 30-year-old woman.
Figure 9.  Follicular adenoma in a 30-year-old woman. Transverse sonogram of the left lobe of the thyroid shows a follicular adenoma with a hypoechoic halo (arrows).
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

44. Vascularity
Chan et al (18) reported that all papillary thyroid carcinomas in their study had some intrinsic blood flow, and they concluded that a completely avascular nodule is very unlikely to be malignant.

45. Figure 11a.  Renal cell carcinoma metastases to the thyroid in a 69-year-old woman.
Figure 11a.  Renal cell carcinoma metastases to the thyroid in a 69-year-old woman. (a) Longitudinal sonogram of the right lobe of the thyroid shows a round hypoechoic nodule (arrows) and an irregular-shaped hypoechoic nodule (arrowheads). (b) Color Doppler sonogram of the round nodule shows increased internal vascularity.
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

46. Figure 11b.  Renal cell carcinoma metastases to the thyroid in a 69-year-old woman.
Figure 11b.  Renal cell carcinoma metastases to the thyroid in a 69-year-old woman. (a) Longitudinal sonogram of the right lobe of the thyroid shows a round hypoechoic nodule (arrows) and an irregular-shaped hypoechoic nodule (arrowheads). (b) Color Doppler sonogram of the round nodule shows increased internal vascularity.
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

47. Figure 12. Follicular adenoma in a 36-year-old woman.
Figure 12.  Follicular adenoma in a 36-year-old woman. Longitudinal color Doppler sonogram of the right lobe of the thyroid shows perinodular flow around a follicular adenoma.
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

48. Hypoechoic Solid Nodule
Marked hypoechogenicity is very suggestive of malignancy.

49. Figure 13.  B cell lymphoma of the thyroid in a 73-year-old woman with Hashimoto thyroiditis.
Figure 13.  B cell lymphoma of the thyroid in a 73-year-old woman with Hashimoto thyroiditis. Transverse sonogram of the left lobe of the thyroid shows a large heterogeneous mass (between calipers) with marked hypoechogenicity when compared with the strap muscles (SM). A normal isthmus (arrow) also is visible. IJV = internal jugular vein.
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

50. Nonspecific US Features
The size of a nodule is not helpful for predicting or excluding malignancy. There is a common but mistaken practice of selecting the largest nodule in a multinodular thyroid for FNA.

51. Number of Nodules
Although most patients with nodular hyperplasia have multiple thyroid nodules and some patients with thyroid carcinoma have solitary nodules, the presence of multiple nodules should never be dismissed as a sign of benignity.

52. Interval Growth of a Nodule
In general, interval growth of a thyroid nodule is a poor indicator of malignancy. Benign thyroid nodules may change in size and appearance over time.
The exception is clinically detectable rapid interval growth, which most commonly occurs in anaplastic thyroid carcinoma but also may occur in lymphoma, sarcoma, and, occasionally, high-grade carcinoma.

53. Recommendations for Thyroid Nodules 1 cm or Larger in Maximum Diameter
Society of Radiologists in Ultrasound Consensus Conference Statement

54. Punctate echogenicities in thyroid nodules.
Punctate echogenicities in thyroid nodules. (a) Sagittal US image of nodule (arrowheads) containing multiple fine echogenicities (arrow) with no comet-tail artifact. These are highly suggestive of malignancy. FNA and surgery confirmed papillary carcinoma. (b) Transverse US image of nodule (arrowheads) containing cystic areas with punctate echogenicities and comet-tail artifact (arrow) consistent with colloid crystals in a benign nodule.
papillary carcinoma
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

55. Figure 4. Benign thyroid nodule in a 51-year-old woman.
Figure 4.  Benign thyroid nodule in a 51-year-old woman. Transverse sonogram of the right lobe of the thyroid shows a colloid nodule with a ring-down artifact (arrow), a finding indicative of inspissated colloid calcification.
Hoang J K et al. Radiographics 2007;27:
©2007 by Radiological Society of North America

56. Punctate echogenicities in thyroid nodules.
Punctate echogenicities in thyroid nodules. (a) Sagittal US image of nodule (arrowheads) containing multiple fine echogenicities (arrow) with no comet-tail artifact. These are highly suggestive of malignancy. FNA and surgery confirmed papillary carcinoma. (b) Transverse US image of nodule (arrowheads) containing cystic areas with punctate echogenicities and comet-tail artifact (arrow) consistent with colloid crystals in a benign nodule.
colloid crystals in a benign nodule
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

57. US images of thyroid nodules of varying parenchymal composition (solid to cystic).
US images of thyroid nodules of varying parenchymal composition (solid to cystic). (a) Sagittal image of solid nodule (arrowheads), which proved to be papillary carcinoma. (b) Sagittal image of predominantly solid nodule (arrowheads), which proved to be benign at cytologic examination. (c) Transverse image of mixed solid and cystic nodule (calipers), which proved to be benign at cytologic examination. (d) Sagittal image of predominantly cystic nodule (calipers), which proved to be benign at cytologic examination. (e) Sagittal image of cystic nodule (arrowheads). FNA of this presumed benign lesion was not performed because the nodule appears entirely cystic.
papillary carcinoma
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

58. proved to be benign at cytologic examination
US images of thyroid nodules of varying parenchymal composition (solid to cystic).
US images of thyroid nodules of varying parenchymal composition (solid to cystic). (a) Sagittal image of solid nodule (arrowheads), which proved to be papillary carcinoma. (b) Sagittal image of predominantly solid nodule (arrowheads), which proved to be benign at cytologic examination. (c) Transverse image of mixed solid and cystic nodule (calipers), which proved to be benign at cytologic examination. (d) Sagittal image of predominantly cystic nodule (calipers), which proved to be benign at cytologic examination. (e) Sagittal image of cystic nodule (arrowheads). FNA of this presumed benign lesion was not performed because the nodule appears entirely cystic.
proved to be benign at cytologic examination
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

59. proved to be benign at cytologic examination
US images of thyroid nodules of varying parenchymal composition (solid to cystic).
US images of thyroid nodules of varying parenchymal composition (solid to cystic). (a) Sagittal image of solid nodule (arrowheads), which proved to be papillary carcinoma. (b) Sagittal image of predominantly solid nodule (arrowheads), which proved to be benign at cytologic examination. (c) Transverse image of mixed solid and cystic nodule (calipers), which proved to be benign at cytologic examination. (d) Sagittal image of predominantly cystic nodule (calipers), which proved to be benign at cytologic examination. (e) Sagittal image of cystic nodule (arrowheads). FNA of this presumed benign lesion was not performed because the nodule appears entirely cystic.
proved to be benign at cytologic examination
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

60. proved to be benign at cytologic examination
US images of thyroid nodules of varying parenchymal composition (solid to cystic).
US images of thyroid nodules of varying parenchymal composition (solid to cystic). (a) Sagittal image of solid nodule (arrowheads), which proved to be papillary carcinoma. (b) Sagittal image of predominantly solid nodule (arrowheads), which proved to be benign at cytologic examination. (c) Transverse image of mixed solid and cystic nodule (calipers), which proved to be benign at cytologic examination. (d) Sagittal image of predominantly cystic nodule (calipers), which proved to be benign at cytologic examination. (e) Sagittal image of cystic nodule (arrowheads). FNA of this presumed benign lesion was not performed because the nodule appears entirely cystic.
proved to be benign at cytologic examination
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

61. US images of thyroid nodules of varying parenchymal composition (solid to cystic).
US images of thyroid nodules of varying parenchymal composition (solid to cystic). (a) Sagittal image of solid nodule (arrowheads), which proved to be papillary carcinoma. (b) Sagittal image of predominantly solid nodule (arrowheads), which proved to be benign at cytologic examination. (c) Transverse image of mixed solid and cystic nodule (calipers), which proved to be benign at cytologic examination. (d) Sagittal image of predominantly cystic nodule (calipers), which proved to be benign at cytologic examination. (e) Sagittal image of cystic nodule (arrowheads). FNA of this presumed benign lesion was not performed because the nodule appears entirely cystic.
FNA of this presumed benign lesion was not performed because the nodule appears entirely cystic
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

62. Role of color Doppler US
Role of color Doppler US. (a) Transverse gray-scale image of predominantly solid thyroid nodule (calipers).
Role of color Doppler US. (a) Transverse gray-scale image of predominantly solid thyroid nodule (calipers). (b) Addition of color Doppler mode shows marked internal vascularity, indicating increased likelihood that nodule is malignant. This was a papillary carcinoma.
papillary carcinoma
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

63. Role of color Doppler US
Role of color Doppler US. (a) Transverse gray-scale image of predominantly solid thyroid nodule (calipers).
Role of color Doppler US. (a) Transverse gray-scale image of predominantly solid thyroid nodule (calipers). (b) Addition of color Doppler mode shows marked internal vascularity, indicating increased likelihood that nodule is malignant. This was a papillary carcinoma.
papillary carcinoma
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

64. The lesion was benign at cytologic examination
Transverse US images of mostly cystic thyroid nodule with a mural component containing flow.
Transverse US images of mostly cystic thyroid nodule with a mural component containing flow. (a) Gray-scale image shows predominantly cystic nodule (calipers) with small solid-appearing mural component (arrowheads). (b) Addition of color Doppler mode demonstrates flow within mural component (arrowheads), confirming that it is tissue and not debris. US-guided FNA can be directed into this area. The lesion was benign at cytologic examination.
The lesion was benign at cytologic examination
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

65. The lesion was benign at cytologic examination
Transverse US images of mostly cystic thyroid nodule with a mural component containing flow.
Transverse US images of mostly cystic thyroid nodule with a mural component containing flow. (a) Gray-scale image shows predominantly cystic nodule (calipers) with small solid-appearing mural component (arrowheads). (b) Addition of color Doppler mode demonstrates flow within mural component (arrowheads), confirming that it is tissue and not debris. US-guided FNA can be directed into this area. The lesion was benign at cytologic examination.
The lesion was benign at cytologic examination
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

66. US features of malignant lymph node
rounded bulging shape
increased size,
replaced fatty hilum
irregular margins
heterogeneous echotexture
calcifications
cystic areas
vascularity throughout the lymph node instead of normal central hilar vessels at Doppler imaging

67. Abnormal cervical lymph nodes.
Abnormal cervical lymph nodes. (a) Sagittal US image of enlarged node (calipers) with central punctate echogenicities, consistent with microcalcifications, shows mass effect on internal jugular vein (V). Node was proved to be metastatic papillary carcinoma. (b) Sagittal US image of enlarged node (calipers) with cystic component. Node was proved to be metastatic papillary carcinoma.
 metastatic papillary carcinoma
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

68. Abnormal cervical lymph nodes.
Abnormal cervical lymph nodes. (a) Sagittal US image of enlarged node (calipers) with central punctate echogenicities, consistent with microcalcifications, shows mass effect on internal jugular vein (V). Node was proved to be metastatic papillary carcinoma. (b) Sagittal US image of enlarged node (calipers) with cystic component. Node was proved to be metastatic papillary carcinoma.
metastatic papillary carcinoma.
Frates M C et al. Radiology 2005;237:
©2005 by Radiological Society of North America

69. US-guided FNA Technique
The needle may be introduced parallel or perpendicular to the transducer, and the needle tip should be carefully monitored during the procedure. 

70. Figure 7a.  Parallel positioning of the fine-gauge needle for thyroid nodule biopsy.
Figure 7a.  Parallel positioning of the fine-gauge needle for thyroid nodule biopsy. This positioning helps maximize the number of needle-generated reflected echoes perpendicular to the sound wave and is preferred by many operators. (a) Diagram shows insertion of the needle in a plane parallel to that of scanning. (b) US image, obtained with the transducer and needle positioned as in a, depicts the entire length of the needle (arrows) within the nodule.
Kim M J et al. Radiographics 2008;28:
©2008 by Radiological Society of North America

71. Figure 7b.  Parallel positioning of the fine-gauge needle for thyroid nodule biopsy.
Figure 7b.  Parallel positioning of the fine-gauge needle for thyroid nodule biopsy. This positioning helps maximize the number of needle-generated reflected echoes perpendicular to the sound wave and is preferred by many operators. (a) Diagram shows insertion of the needle in a plane parallel to that of scanning. (b) US image, obtained with the transducer and needle positioned as in a, depicts the entire length of the needle (arrows) within the nodule.
Kim M J et al. Radiographics 2008;28:
©2008 by Radiological Society of North America

72. Figure 8a.  Perpendicular positioning of the fine-gauge needle for thyroid nodule biopsy.
Figure 8a.  Perpendicular positioning of the fine-gauge needle for thyroid nodule biopsy. (a) Diagram shows insertion of the needle in a plane perpendicular to that of scanning. A shorter needle may be used with this option, and it is less likely that the carotid artery or jugular vein may be punctured. (b) US image, obtained as the needle crossed from the skin entry site through the tissues of the neck and into the nodule, shows only the needle tip (arrow) where it intersected with the scanning plane.
Kim M J et al. Radiographics 2008;28:
©2008 by Radiological Society of North America

73. Figure 8b.  Perpendicular positioning of the fine-gauge needle for thyroid nodule biopsy.
Figure 8b.  Perpendicular positioning of the fine-gauge needle for thyroid nodule biopsy. (a) Diagram shows insertion of the needle in a plane perpendicular to that of scanning. A shorter needle may be used with this option, and it is less likely that the carotid artery or jugular vein may be punctured. (b) US image, obtained as the needle crossed from the skin entry site through the tissues of the neck and into the nodule, shows only the needle tip (arrow) where it intersected with the scanning plane.
Kim M J et al. Radiographics 2008;28:
©2008 by Radiological Society of North America

74. Radiopharmaceuticals
Radioactive Iodine 131 (scan and uptake) used for therapy
Radioactive Iodine 123 (scan and uptake) is the radioisotope of choice. The 13.3-hour half-life, the 159-keV principal photon, and the absence of particulate emission allow for good imaging with modest patient exposure. However, this isotope is cyclotron produced and relatively expensive, and the short half- life necessitates frequent shipments from the producer.
Free Tc99m (scan only)

75. Ablation of Benign Thyroid diseases with I131
Graves’ disease is ablated with mCi of I131.
Toxic nodular goiter (single nodule or multinodular) is ablated with mCi of I131

76. Ablation of Thyroid cancer with I131
This is effective in differentiated thyroid cancer only(papillary and follicular thyroid cancers).
Both are originated from follicular cell which is the functional cell in thyroid tissue (build thyroid hormone by utilizing iodine).

77. Thyroid Cancer Ablation
Once follicular cell (benign or malignant) takes up radioactive iodine I131, beta particles will be emitted causing serious damage to cell components. These cells become nonfunctional and then die.
Ablation is not helpful in medullary thyroid cancer and anaplastic carcinoma.

78. Protocol Total thyroidectomy is required before ablation.
mCi of I131 is needed for ablation of remnant thyroid tissue post total thyroidectomy.

79. Radiation Protection
Cancer patients should be isolated in special room (leaded walls) to prevent others from radiation coming from the patient.
Isolation is usually for 2-3 days.
Once the residual iodine is coming down to 30 mCi and less, the patient can be discharged.
Patient is followed up with thyroglobulin to detect recurrence and if needed nuclear scan

80. Remnant thyroid tissue

81. Remnant thyroid tissue with metastatic cervical adenopathy

82. Remnant thyroid tissue with metastatic cervical adenopathy

83. Thank you