Thyroid

• What Rf are used for the thyroid?

  • Iodine-131
  • Iodine-123
  • 99mTc-pertechnetate
  • 99mTc-MIBI (sestamibi)
• Iodine-131:

  • t1/2 = 8 days-long
  • beta emission,
  • low price and readily available,
  • used for thyroid therapy/treatment,
  • used for whole-body scanning for detection of thyroid cancer metastases
• Iodine-123:

  • t1/2 = 13h,
  • gamma emission,
  • more expensive,
  • optimal for imaging
• 9mTc-pertechnetate:

  • t1/2 = 6h,
  • gamma emission,
  • readily available,
  • optimal for imaging (w/ salivary glands)
• 99mTc-pertechnetate is preferred over radioiodine when

  • the patient has recently received thyroid-blocking agents,
  • is unable to take oral I-123,
  • when the study must be completed in less than 2h
• •99mTc-MIBI (sestamibi) used in special cases for thyroid and parathyroid scintigraphy.
• Different isotopes of iodine in diagnostic and screening techniques?

  • Diagnosis: 123-I (for thyroid imaging / examination)
  • Treatment: 131-I (for hyperthyroidism – emits beta particles)
  • Radioactive iodine treatment (for thyroid carcinoma)
• What is the basic imaging technique in endocrinology and where and why is it used – main indications?

  Ultrasound is the basic imaging technique used in endocrinology and is indicated in the

  • Evaluate Nodules, Lumps + Exact measurement of size -
  • Examination of Cysts
  • Monitor the success of anti-thyroid treatment for graves’ disease
  • Guiding for fine needle aspiration
• What are thyroid nodules?

  Thyroid nodules are solid or fluid-filled lumps that form within your thyroid
• how we can distinguish between thyroid cancer and adenoma?

  • Ultrasound + biopsy
  • Hypo echoic nodule with micro-calcification, central blood flow / irregular border
  • *** USG cannot accurately distinguish between thyroid cancer and thyroid adenoma. Only histology can do that.
• RADIOIODINE UPTAKE TEST (RAI)

  based on the principle that the orally administered RF is concentrated by the thyroid gland in a way that reflects the gland’s handling of dietary iodine, therefore showing the functional status of the gland.
• what Rf is used in radioiodine uptake test?

  • Iodine-131
  • Iodine-123
  • 99m-Tc-pertechnetate
• Interpretation of radioiodine uptake test

  • Norm = 10-15% after 2 hours
  • High = Graves' disease, toxic nodular goiter
  • Low = subacute thyroiditis
• What Rf is used in thyroid scintigraphy?

  • Iodine-131
  • Iodine-123
  • Tc-99m-pertechnetate
  • 99mTc-MIBI
• What projections are taken in thyroid scintigraphy?

  • right anterior oblique,
  • anterior
  • left anterior oblique
• thyroid scintigraphy procedure

  1. Fasting before exam
  2. Iodine-123: Image 2 hours after admin
  3. Iodine-131: Image 24 hours after admin (for carcinomas)
  4. Tc-99m-pertechnetate: 15-30 min after admin (do not swallow)
• what position should a patient be during a thyroid scintigraphy?

  supine position w/ neck elevated
• Uptake of 99mTc could be decreased by what?

  • Administration of iodinated contrast materials,
  • Intake of stable iodine in any form (seafood, sea fish, mineral water)
  • Anti-thyroid agents and other drugs with iodine.
• Indications for thyroid scintigraphy?

  • Determine the functional status of the gland
  • Differentiate causes of Hyperthyroidism
  • Differentiate between hyperthyroidism and other causes of thyrotoxicosis
  • Assessment of palpable nodules
  • Find ectopic thyroid site
  • Neonatal hypothyroidism, exclusion of congenital agenesis of the thyroid gland (neonates ages 2/3 weeks)
  • Postoperative assessment
• contraindications for thyroid scintigraphy?

  pregnancy and breast feeding (must be stopped permanently if I-131 is administered)

  allergy
• Pathological findings for thyroid scintigraphy

  • hot nodules
  • cold nodules
  • multinodular goiter
  • diffuse toxic goiter
• Cold nodules are present in decreased thyoid function, such as

  • Cysts,
  • benign adenomas,
  • malignant neoplasm,
  • later stages of Hashimoto thyroiditis,
  • autoimmune thyroiditis,
  • metastasis,
  • abscess,
  • hemorrhage.
• Hot nodules are present in areas of hyperfunction in the thyroid, such as Graves' disease, early stage Hashimoto's thyroiditis, and toxic goiter.
• How to differentiate between thyroid malignant and benign cancer?

  • Fine needle aspiration
  • cytology,
  • BIOPSY = Histological investigation
• what are the therapeutic uses of Iodine-131?

  • thyrotoxicosis
  • thyroid carcinoma
• what is radionuclide therapy?

  therapy with iv administration of radioactive agents as part of cancer treatment to control or kill malignant cells.
• what us the therapeutic strategy for thyrotoxicosis?

  antithyroid drugs

  surgery

  Iodine-131
• In thyrotoxicosis, Iodine-131 is applied at low doses to eliminate thyroid function. At high doses, the function is eliminated in weeks.
• what occurs after the elimination of thyroid function?

  hypothyroidism
• what are the symptoms post thyrotoxicosis therapy?

  • sore throat
  • dysphagia
• when does the therapeutic effect occur in thyrotoxicosis threatment?

  after 3-6 weeks
• types of thyroid carcinoma

  • papillary
  • follicular
  • medullary
  • anaplastic
• How do we treat patients with thyroid carcinoma?

  • thyroidectomy
  • radioactive iodine
  • radiotherapy
  • chemotherapy
• Do they have to be hospitalized or not during treatment?

  yes
• Iodine-131 thrapy

  • High doses are required -> 1-8 GBq
  • patient needs to confined at nuclear department
  • showers of 3 mins
  • storing of human residues
• what imaging is this and what pathology is shown?

  Thyroid gland scintigraphy; Multiple thyroid adenoma

  
• what imaging is this and what pathology is shown?

  Thyroid gland scintigraphy; Thyroid adenoma

  
• what imaging is this and what pathology is shown?

  Thyroid gland scintigraphy; congenital agenesis of the thyroid

  
• what pathology is shown?

  hot nodule

  
• what pathology is shown? 


  cold nodule