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Imaging of the thyroid

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DR.SHARIQ A SHAH RADIODIAGNOSIS SKIMS SRINAGAR

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Imaging of the thyroid

  1. 1. THYROID IMAGING MODERATOR: DR NASEER AHMAD CHOH SR RESIDENT INCHARGE: DR TEHLEEL ALTAF PRESENTER: DR SHARIQ AHMAD SHAH
  2. 2. OVERVIEW • Anatomy and embryology • Imaging modalities • Diffuse thyroid disease • Evaluation of a thyroid nodule • Recent developments
  3. 3. ANATOMY OF THYROID SIZE: NEWBORN: 18-20 mm long 8-9 mm AP ADULTS: 4-6 cm long 13- 18 mm AP isthmus :4-6 mm VOLUME: 19.6 ml males 18.6 ml females
  4. 4. EMBRYOLOGY • Develops from median and lateral anlages. • Median anlage: arises in the middle of oropharynx at 4th to 5th gestation age , gives rise to follicular tissue. • Lateral anlage: arise from ultimobrachial bodies (derivatives of fourth and fifth branchial pouches), gives rise to parafollicular c cells. • Fusion occurs by tenth week forming bilobed gland
  5. 5. IMAGING MODALITIES • X RAY • USG • RADIONUCLIDE IMAGING • CT / MRI
  6. 6. X ray • Enlargement • Tracheal shift or narrowing • calcifications • Retrosternal extension • Bone destruction • Pulmonary metastasis
  7. 7. Nuclear scintigraphy • Agents used are I-123, I-131, TC-99 • Done with a gamma scintillation camera • Normal gland shows homogenous radionuclide uptake and distribution
  8. 8. INDICATIONS • Assessment of anatomy • Assessment of function • Post operative assessment • Detection of nodule – hot or cold or warm • Detection of functional metastatic tissue in known case of thyroid ca. • Detection of retrosternal goitre.
  9. 9. CONTRAINDICATIONS • Pregnancy • Hypersensitivity to iodine • Discard breast milk for 26 hrs after injection
  10. 10. PREPARATION • Stop antithyroid drugs 2 days before. • Stop thyroid hormones 1 week before. • Avoid iodinated contrast 4 weeks before. • Stop iodine rich foods ( fish , cauliflower) a week before. • Done after 4 hr fasting.
  11. 11. Normal thyroid scan
  12. 12. Diffuse toxic goitre
  13. 13. DIFFERENTIAL DIAGNOSIS COLD NODULE (8-25% chances of malignancy) • Thyroiditis • Cyst • Fibrosis • Non functioning adenoma • Multinodular goitre • Malignancy HOT NODULE (Malignancy rare) • Functioning adenoma • Thyroiditis
  14. 14. USG • First choice of evaluation • Acessible, inexpensive and non invasive • High spatial resolution- 0.5 to 1 mm • Size and volume measurements. • Doppler USG ( PSV of major thyroid A = 20-40cm /s and intraparenchymal arteries= 15-30cm/s)
  15. 15. Congenital anomalies • Hypoplasia/aplasia • Ectopia • Thyroglossal cyst
  16. 16. Diffuse thyroid disease • Thyroiditis Acute suppurative Sub acute granulomatous (De Quervans) Chronic lymphocytic ( Hashimoto) Invasive fibrous throiditis (Riedels) • Graves disease
  17. 17. Sub acute thyroiditis
  18. 18. Hashimoto - micronodularity
  19. 19. Hasimoto- coarse septation
  20. 20. Graves disease
  21. 21. Invasive fibrous ( Riedel’s thyroiditis)
  22. 22. EVALUATION OF THYROID NODULE • NODULE: a discrete lesion that is radiologically distinct from sorrounding parenchyma. • Some Palpable lesions may not be radiologically distinct….not considered as nodule • Non-palpable nodules detected on imaging studies --- incidentalomas
  23. 23. • Prevalence • Incidence of malignancy : 9-13 %
  24. 24. • Generally only nodules > 1 cm should be evaluated. • Long term studies showed no difference in outcome between patients with biopsy proven carcinoma < 1 cm undergoing thyroidectomy and those with no surgical intervention. ( Ito et al, world j surg 2010;34;28-35)
  25. 25. Serum TSH • Serum TSH should be measured during initial evaluation • If serum TSH is subnormal, a radionuclide scan should be performed. • If serum TSH is normal or elevated, a radionuclide scan should not be performed as the initial imaging modality. Serum thyroglobulin measurement • Routine measurement of serum Tg is not recommended. ( revised ATA 2015)
  26. 26. TSH and Radionuclide scan • A higher TSH level , even within upper part of refrence range is associated with increased risk of malignancy in a thyroid nodule • If TSH is low, risk of malignancy depends on tracer uptake in scan Hot nodule : rarely harbours malignancy, no need for cytology. Cold nodule: non functioning
  27. 27. USG
  28. 28. SUSPICIOUS NODULE 1. Taller than wide shape 2. Spiculated or irregular margins . 3. Markedly hypoechoic nodule. 4. Predominant solid composition. 5. Microcalcification in a predominantly solid nodule (3 fold risk). 6. Macrocalcification in a solid nodule ( 2 fold risk) 7. Absence of halo. 8. Intranodular vascularity.
  29. 29. AMERICAN THYROID ASSOCIATION NODULE GUIDELINES , JANUARY 2016. •
  30. 30. HIGH HIGH INTDD LOW VERY LOW
  31. 31. Thyroid nodule evaluation and management algorithm
  32. 32. Recommendations for initial follow up of nodules with BENIGN FNAC
  33. 33. 1. Nodules with high suspicion US pattern: repeat US and USG guided FNAC within 12 months. 2.Nodules with low to intermediate suspicion US pattern: repeat US at 12 months rapid growth or development of new suspicious features repeat FNAC
  34. 34. 3. Nodules with very low suspicion: utility of surveillance not known 4. If a nodule has undergone repeat FNAC with a second benign cytology no need to follow up with US
  35. 35. Follow up for nodules that do not meet FNAC criteria
  36. 36. high suspicion us pattern repeat us in 6-12 months low or intermediate suspicion us pattern repeat us at 12- 24 months >1 cm nodules with very low suspicion pattern repeat us at > 24 months < 1 cm nodules with very low suspicion us pattern no need of follow up
  37. 37. CROSS SECTIONAL IMAGING • Important adjunctive anatomic information. • Better delineation of lesion within thyroid. • Detection of lymph node metastasis. • Extension of disease to adjacent tissues of neck. • Assess paraspinal muscle, esophageal, tracheal, jugular vein invasion.
  38. 38. CT SCAN • On NCCT thyroid appears as two wedge shaped structures of homogenous attenuation with density of 80- 100 HU because of iodine content • Enhances homogenously on iv contrast. • Contrast interferes with radionuclide scan. so scan should be performed either before CT or 6 weeks after it.
  39. 39. NCCT CECT
  40. 40. GOITRE
  41. 41. MRI • Dedicated surface coils centered over thyroid. • T1 : thyroid shows homogenous signal intensity slightly greater than that of neck muscles. • T2: gland is hyperintense relative to neck muscles • Gadolinium contrast can be administered. • Gadolinium does not interfere with iodine uptake and organification, so can be used in conjunction with scintigraphy.
  42. 42. T1W T2W
  43. 43. RECENT DEVELOPMENTS
  44. 44. PERFUSION CT • Measures temporal changes in tissue density after iv contrast. • Quantifies abnormal vasculature within tumours, thus allowing assessment of tumour agressiveness. • Benign tumours have been found to show low BF and MTT compared to malignant tissue.
  45. 45. DIFFUSION WEIGHTED MRI: • Performed with the aim of differentiating malignant from benign lesions. • This technique evaluates rate of microscopic water diffusion in tissues. • All benign nodules have higher mean ADC value than malignant nodules.
  46. 46. CONTRAST ENHANCED ULTRASOUND • Enhancement pattern is recognised. • Ring enhancement correlates with benign lesions while heterogenous enhancement correlates with malignant lesions.
  47. 47. COLLOID CYSTIC PAPILLARY CA
  48. 48. ELASTOGRAPHY • Obtains information about tissue stiffness non invasively. • Elastography score (ES) is assigned based on colour pattern of lesion relative to sorrounding tissue. • Red ( soft tissue), green ( intermediate degree of stiffness), blue ( anelastic tissue). • An ES of 4-5 is highly predictive of malignancy (sensitivity 94%).
  49. 49. ELASTOGRAM PATTERNS • PATTERN 1: Whole nodule elastic • PATTERN 2: Most part elastic, inconsistent inelastic areas • PATTERN 3: Constant portions of anelastic areas • PATTERN 4: Uniformly anelastic
  50. 50. BENIGN NOD HYPERPLASIA PAPILLARY CA
  51. 51. PET SCAN • Used in follow up of patients with thyroid cancer due to incresed glucose metabolism by malignant tumours • May be useful in tumours which don’t concentrate iodine. • In patients with raised thyroglobulin levels after thyroidectomy, whole body scans are obtained to identify regions of FDG uptake.
  52. 52. MAGNETIC RESONANCE SPECTROSCOPY
  53. 53. OPTICAL COHERENCE TOMOGRAPHY
  54. 54. Thyriod ultrasound reporting lexicon-- TIRADS
  55. 55. Refrences 1. Carol rumack, diagnostic ultrasound 4e 2. David sutton,text book or radiology & imaging 3. Journal am coll radiol 2015;12:1272-1279 4. Open journal of radiology,2013,3 103-107 5. Radiology;vol 260:number 3-september 2011 6. Radiographics 2014;34:276-293
  56. 56. THANKS

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