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18 - Thyroid Isotope Scan

18 - Thyroid Isotope Scan - ‫‪THYROID ISOTOPE‬‬...

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Unformatted text preview: ‫‪THYROID ISOTOPE‬‬ ‫‪SCAN‬‬ ‫‪SCAN‬‬ ‫الدكتور قصي المقبل‬ ‫أستاذ مشارك- قسم الشعة والطب‬ ‫النووي‬ ‫كلية الطب-جامعة العلوم والتكنولوجيا‬ ‫الردنية‬ Thyroid Diseases Thyroid Thyrotoxicosis Hypothyroidism Thyroid nodules Thyrotoxicosis VS Hyperthyroidism Hyperthyroidism Thyrotoxicosis: a group of symptoms and group signs due to elevated thyroid hormones in the body of any cause. the Hyperthyroidism: a group of symptoms group and signs due to increased production of thyroid hormones by hyper functioning thyroid gland. thyroid Causes of Thyrotoxicosis Causes Hyperthyroidism 1- Diffuse toxic goiter (Graves’ disease) 12- Single toxic nodule 23- Toxic multi-nodular goiter 3 Early phase sub-acute thyroiditis Exogenous thyroid hormone intake Thyroiditis and exogenous Thyroiditis thyroid hormone intake thyroid 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. the Exogenous thyroid hormone intake: Exogenous 1- By mistake 12- with weight loss pills 2- Thyrotoxicosis and TFT Thyrotoxicosis TSH is always suppressed in TSH thyrotoxicosis. thyrotoxicosis. TSH is the most sensitive test for thyroid TSH function and it is the screening test for thyroid dysfunction. thyroid If TSH is abnormal, T3 and T4 levels can If be obtained in order to determine the severity of the disease. T3 and T4 are usually elevated in thyrotoxicosis. usually TFT and Thyroid scan TFT Thyrotoxicosis= suppressed TSH and Thyrotoxicosis= elevated T3/T4. elevated Based on TFT, the exact cause of Based thyrotoxicosis can not be determined. thyrotoxicosis Thyroid scan is a very helpful tool in Thyroid differentiating between various causes of thyrotoxicosis. thyrotoxicosis. Thyroid scan and uptake Thyroid Radioactive Iodine (RAI) is used for Radioactive thyroid scan and uptake. thyroid RAI is given orally. RAI Image and uptake are obtained after 24 Image hours hours Follicular cell traps Iodine and organifys it Follicular to be incorporated with thyroid hormone. to Imaging Imaging Symmetric or asymmetric lobes. Homogeneous or inhomogeneous uptake Nodules; cold or hot Normal Variants Normal 24-hour RAI uptake 24-hour Measure photons in the given RAI by a Measure special probe (uptake probe) just before taking RAI. taking After 24 hours, measure photons in the After neck (thyroid gland). neck Calculate % of photons concentrated in Calculate thyroid gland. Thyroid Uptake Probe 24 hr Radioiodine Uptake 24 Example: 40% 24-hour RAI uptake means Example: that 40% of photons (RAI) has been taken by thyroid gland. by Normal range of 24 RAI uptake is 10%20% (mean of 15%). Diffuse Toxic goiter (Graves’ Disease) Diffuse Diffuse enlargement of thyroid gland. Homogeneous uptake. No significant focal abnormalities No (nodules). (nodules). 24-hour RAI uptake is elevated, usually > 24-hour 35% (mean of 40%). 35% Graves’ Disease Graves’ Single Toxic Nodule Single Single hot nodule (independent of TSH or Single autonomous). autonomous). Rest of thyroid gland is poorly visualized Rest due to low TSH level (TSH dependant). due 24-hour RAI uptake is slightly elevated, 24-hour usually around 20%. usually Toxic Nodule Toxic Hot Nodule Hot Toxic Multi-Nodular Goiter Toxic Mild inhomogeneous uptake in thyroid Mild gland. gland. Multiple cold and hot nodules in both Multiple thyroid lobes. thyroid 24-hour uptake is mildly elevated, usually 24-hour between 20%-30%. between Multi-nodular Goiter Multi-nodular • 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. some Multi-nodular Goiter Multi-nodular Early Phase Sub-acute Thyroiditis Thyroiditis Inhomogeneous uptake could be mild or Inhomogeneous severe. In some cases thyroid gland is not visualized. visualized. No significant focal abnormalities No (nodules). (nodules). 24-hour RAI uptake is low, usually < 5%. 24-hour Sub-acute Thyroiditis Sub-acute Hypothyroidism Hypothyroidism The main cause is chronic thyroiditis The (Hashimoto’s thyroiditis). (Hashimoto’s TSH is elevated. Thyroid scan does not have significant Thyroid diagnostic value in this entity. diagnostic However, if there is nodule/nodules However, confirmed by physical examination and ultrasound, thyroid scan may be helpful. ultrasound, Hypothyroidism Hypothyroidism Thyroid Nodules Thyroid Nodules are usually found by physical Nodules examination or by ultrasound. examination The patient is usually euthyroid. Thyroid scan is helpful in characterizing Thyroid thyroid nodule. It can differentiate between hot and cold nodules. hot COLD and HOT Nodules COLD Cold Nodule Cold Thyroid Nodules-cont.. Thyroid 10%-20% of cold nodules are malignant. FNA is needed for all cold nodules. There is no need to do 24-hour RAI There uptake. uptake. Thyroid scan can be done using free Thyroid Tc99m Tc Radiopharmaceuticals Radiopharmaceuticals Radioactive Iodine 131 (scan and uptake) Radioactive Iodine 123 (scan and uptake) Free Tc99m (scan only) Ablation of Benign Thyroid diseases with I131 diseases Graves’ disease is ablated with 10-15 mCi Graves’ of I131. of Toxic nodular goiter (single nodule or Toxic multinodular) is ablated with 25-30 mCi of I131 I131 Ablation of Thyroid cancer with I131 I131 This is effective in differentiated thyroid This cancer only. cancer Differentiated thyroid cancers are papillary Differentiated and follicular thyroid cancers. and Both are originated from follicular cell Both which is the functional cell in thyroid tissue (build thyroid hormone by utilizing iodine). (build Thyroid Cancer Ablation Thyroid Once follicular cell (benign or malignant) Once 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 Ablation cancer and anaplastic carcinoma. cancer Protocol Protocol Total thyroidectomy is required before Total ablation. ablation. TSH should rise to more than 25 mlU\L. 100-200 mCi of I131 is needed for ablation 100-200 of remnant thyroid tissue post total thyroidectomy. thyroidectomy. Radiation Protection Radiation Cancer patients should be isolated in Cancer special room (leaded walls) to prevent others from radiation coming from the patient. patient. Isolation is usually for 2-3 days. Once the residual iodine is coming down Once to 30 mCi and less, the patient can be discharged. Remnant thyroid tissue Remnant Remnant thyroid tissue with metastatic cervical adenopathy metastatic Remnant thyroid tissue with metastatic cervical adenopathy metastatic ...
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