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Thyroid Scan

Thyroid Scan

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Thyroid Scan

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  1. Thyroid Scan รศ.พญ. มลฤดี เอกมหาชัย หน่วยเวชศาสตร์นิวเคลียร์ ภาควิชารังสีวิทยา คณะแพทยศาสตร์ มหาวิทยาลัยเชียงใหม่

  2. Normal and Aberrant Locations of Thyroid Tissues

  3. Hypothalamus- Pituitary- Thyroid Axis

  4. Iodide Metabolisms 1. Trapping 2. Organification 3. Couplings 4. Hormonal release

  5. Iodide Metabolisms 1. Trapping :Active transport 2. Organification : Iodide ----------> Neutral Iodine Iodine + Tg -----> MIT, DIT MIT = Mono-iodinated tyrosine DIT = Di-iodinated tyrosine Peroxidase

  6. Iodide Metabolisms 3. Couplings : MIT + DIT = Triiodothyronine (T3) DIT + DIT = Thyroxine (T4) 4. Hormonal release : T3 & T4 -Free form -Bound form

  7. Radiopharmaceuticals 1. Iodine-125 :In vitro TFT • T1/2 = 60 days • r-energy 29-35 keV 2.Iodine-123 :Ideal isotope • T1/2 = 13 hours • r-energy 159 keV • Cyclotron produced isotope

  8. Radiopharmaceuticals 3. Iodine-131 :Oral • T1/2 = 8.06 days • r-energy 364 keV • B-energy 192 keV 4.Tc-99m pertechnatate :IV • T1/2 = 6 hours • r-energy 140 keV

  9. Thyroid Function Studies 1. Iodine uptake test (Thyroid uptake test) 2. Perchlorate washout test 3. T3 suppression test 4. TSH stimulation test

  10. Indications for Iodine-131 Uptake 1. Clinical hyperthyroidism, but with equivocal thyroid function tests 2. R/O subacute thyroiditis 3. Known case of hyperthyroidism with plan to give low dose Iodine-131 treatment

  11. Iodine Uptake Test • Methods: • Oral iodine-131 dose 20 uCi • Serial thyroid uptake at 2, 24 & 48 hrs • % Iodine uptake • Net thyroid counts X 100 % Net counts of standard dose

  12. Normal Iodine Uptake • 2 hours = 10-30 % • 24 hours = 20-60 % • 48 hours = 20-60 %

  13. Factors Affecting Increased 131-I Uptake 1. Hyperthyroidism 2. Rebound effect 3. Iodine deficiency 4. Recovery phase of subacute thyroiditis 5. Compensatory dyshormogenesis

  14. Factors Affecting Decreased 131-I Uptake 1. Hypothyroidism 2. Medications : ATD, Thyroid hormones 3. Iodine overload :Diet, Contrast media etc. 4. Goitrogens 5. Subacute thyroiditis, early phase

  15. Indications for Thyroid Scan 1. Thyroid nodule(s) 2. Diffuse or multinodular goiter 3. Clinical hyper- or hypothyroidism 4. Evaluation of substernal mass 5. R/O Ectopic thyroid tissue 6. Subacute thyroiditis, early phase 7. Patient with previous Hx of H & N RT

  16. Normal Thyroid Scan

  17. Normal Thyroid Scan

  18. Thyroid Nodule 1. Cold nodule 2. Hot nodule 3. Warm nodule

  19. Single Cold Nodule

  20. Single Cold Nodule

  21. Causes of Cold Nodule • Colloidal cyst • Hypofunctioning adenoma • Thyroid carcinoma 15-25 % • Others :focal thyroiditis, abscess, hematoma, lymphoma, metastasis, parathyroid adenoma, lymph node enlargement (rare) 70-75 %

  22. Hot Nodule Ant RAO

  23. Hot Nodule

  24. Causes of Hot Nodule • Hyperfunctioning adenoma(s) • Anatomical variant • Thyroid carcinoma 2 % • Compensatory hypertrophy

  25. Warm Nodule

  26. Causes of Warm Nodule • Functioning adenoma • Anatomical variant • Thyroid carcinoma 4 % • Deep seated cold nodule

  27. Diffuse Goiter • Euthyroid • Simple goiter or • Adolescent goiter • Hyperthyroidism • Diffuse toxic goiter (Graves’ disease)

  28. Simple Goiter

  29. Simple Goiter

  30. Graves’ Disease

  31. Graves’ Disease

  32. Graves’ Disease

  33. Nodular Goiter • Euthyroid • Multinodular goiter • Hyperthyroidism • Single :Nodular toxic goiter • Multiple :Plummer’s disease • Hypothyroidism • Hashimoto’s thyroiditis

  34. Multinodular Goiter

  35. Multinodular Goiter

  36. Multinodular Goiter

  37. Nodular Toxic Goiter

  38. Nodular Toxic Goiter

  39. Plummer’s Disease

  40. Substernal Goiter

  41. Subacute Thyroiditis

  42. Subacute Thyroiditis

  43. Normal Thyroid Scan

  44. Congenital Hypothyroidism • Thyroid agenesis • Ectopic thyroid • Congenital organification defect • Normal location of thyroid gland with diffuse decreased uptake

  45. Thyroid Agenesis

  46. Thyroid Agenesis

  47. Ectopic Thyroid Ant Rt.lateral

  48. Ectopic Thyroid

  49. Ectopic Thyroid

  50. Ectopic Thyroid