thyriod nulear medicine

DIAGNOSTIC NUCLEAR MEDICINE : 

DIAGNOSTIC NUCLEAR MEDICINE DR:MUSTAFA IBRAHIM

PROCEDURE AND RADIOPHARMACEUTICALS : 

PROCEDURE AND RADIOPHARMACEUTICALS Tc99m : Half Life = 6 hours Decays by isomeric transition. Generator produced. Gamma energy = 140 keV It is trapped in the thyroid gland by active transport. Only 2-4% of the administered dose is trapped in the thyroid. Peak activity is after 20-30 min of IV injection.

Cont . : 

Cont . Iodine-123 : Decays by electron capture. Half life =13.6 hours. Gamma energy =159 keV Cyclotron produced. Dose = 200-400uCi. PO capsule, scan obtained after 4 hr then after 24 hr. Agent of choice for evaluating retrosternal goiter.

Cont… : 

Cont… Iodine131: B minus decay. Half life = 8 days. Reactor produced. Gamma energy = 364keV Dose ( thyroid scan) = 100uCi Scan is obtained after 24 hours. Because of the beta emission, this agent is useful for therapeutic purposes.

NORMAL SCAN : 

NORMAL SCAN

INDICATIONS : 

INDICATIONS Congenital anomalies. Goiter Abnormal thyroid function: a-Hypothyroidism b-Hyperthyroidism Nodules

Congenital Anomalies : 

Congenital Anomalies Dyshormonogenesis. Congenital absence. Ectopic thyroid tissue: Lingual \ sublingual thyroid. Thyroglossal cyst. Strauma ovarii.

Dyshormonogenesis : 

Dyshormonogenesis An organification defect that is most commonly due to peroxidase enzyme deficiency. Increased uptake in an enlarged gland. Clinical picture of hypothyroidism.

Ectopic Thyroid Tissue : 

Ectopic Thyroid Tissue Lingual \ Sublingual Thyroid: Patient presents with a neck or lingual mass. Euthyroid or hypothyroid In more than 70% of cases normal thyroid tissue is not visualized.

Cont .. : 

Cont .. Thyroglossal duct cyst: Midline neck mass. Majority of patients have normal thyroid tissue. The cyst could contain ectopic thyroid tissue. Surgery is contraindicated in case of ectopic thyroid tissue because this could be the only functioning thyroid tissue.

Cont .. : 

Cont .. Struma ovarii: Presence of ectopic thyroid tissue in ovarian teratomas. The patient may develop hyperthyroidism if this tissue became hyper-functioning.

Goiter and Hyperthyroidism : 

Goiter and Hyperthyroidism High uptake: 1. Diffuse toxic goiter (Graves disease). 2.Toxic nodule. 3.Toxic multi nodular goiter. Low uptake: 1. S.A thyroiditis 2. Chronic thyroiditis 3. High Iodine or thyroxin uptake

Goiter and Normal Thyroid Function : 

Goiter and Normal Thyroid Function Normal uptake: -Simple diffuse goiter Low patchy uptake: -Multinodular goiter ( MNG )

Goiter and hypothyroidism : 

Goiter and hypothyroidism Chronic thyroiditis (Hashimoto’sThyroiditis) Dyshormonogenesis: (Peroxidase def. )

Diffuse Toxic Goiter(Graves Disease) : 

Diffuse Toxic Goiter(Graves Disease) Autoimmune disorder: the presence of TSH receptor antibodies called Thyroid Stimulating Immunoglobulin or LATS. Age of presentation : 30-40 years . Male : Female = 1:7 Symptoms of thyrotoxicosis. Increased T3, T4 and low TSH.

Risk of Malignancy in Graves : 

Risk of Malignancy in Graves Although patients with Graves Disease are not at an increased risk for thyroid cancer, cold nodules may be more aggressive in this patient population.

Treatment of Graves Disease : 

Treatment of Graves Disease Surgery. Anti-thyroid drugs: Propylthiouracil Methimazole Iodine 131 therapy.

Thyroid Nodules : 

Thyroid Nodules Hot nodules: a-Single b-Multiple Cold nodules: a-Multi nodular goiter: - Simple M.N.G - M.N.G with predominant large cold nodule b- Solitary cold nodule:- - In a normal functioning thyroid gland - On top of graves disease

Solitary Toxic Nodule : 

Solitary Toxic Nodule An infrequent cause of hyperthyroidism Anti-thyroid drugs are not the treatment of choice . Iodine 131 is the preferred therapy.

D.Dx of Cold Thyroid Nodule : 

D.Dx of Cold Thyroid Nodule Adenoma Cyst Carcinoma Multinodular goiter Hashimoto's thyroiditis Subacute thyroiditis Effect of prior operation or 131I therapy Thyroid hemiagenesis Metastasis Parathyroid cyst or adenoma Thyroglossal cyst Nonthyroidal lesions Inflammatory or neoplastic nodes Cystic hygroma Aneurysm Bronchocele Laryngocele

Scan sensitivity : 

Scan sensitivity Scan sensitivity is related to the size of nodule: 6.6-10 mm -------- < 10 % 1-2 cm------------- 92% >2cm--------------- 100%

Risk of malignancy : 

Risk of malignancy Risk of malignancy in cold nodules is about 10-20% Risk of malignancy increases with: 1-Male 2-<40 years 3-Hx of radiation exposure 4-Symptomatic Patients: Vocal cord paralysis, Dysphagia

THYROIDITIS : 

THYROIDITIS Inflammatory thyroid diseases accounts for about half of all clinical thyroid disorders.

Types of Thyroiditis : 

Types of Thyroiditis Chronic lymphocytic thyroiditis (Hashimoto) Subacute lymphocytic thyroiditis Subacute granulomatous thyroiditis (De Quervain) Acute suppurative thyroiditis

Application of Thyroid Scan in Thyroididts : 

Application of Thyroid Scan in Thyroididts Application of thyroid scan in thyroiditis is of great value in differentiating between subacute thyroiditis and other causes of thyrotoxicosis ( Graves’ Disease and Toxic Nodule).

Treatment: : 

Treatment: Treatment includes the control of clinical symptoms of hyper- and hypothyroidism, until resolution of the inflammatory process has occurred.

Tumours Of The Thyroid Gland : 

Tumours Of The Thyroid Gland

I ) Adenomas : 

I ) Adenomas Follicular         1. Colloid variant         2. Embryonal         3. Fetal         4. Hurthle cell variant Papillary (probably malignant) Teratoma

II) Malignant Tumors : 

II) Malignant Tumors A. Differentiated:    1. Papillary adenocarcinoma    a. Pure papillary adenocarcinoma b.Mixed papillary and follicular carcinoma    2. Follicular adenocarcinomas a. Malignant adenoma b. Hurthle cell carcinoma(oxyphil carcinoma) c. Clear-cell carcinoma. d. Insular carcinoma

Cont .. : 

Cont .. B. Medullary carcinoma (not a tumor of follicular cells) C. Undifferentiated 1. Small cell 2. Giant cell 3. Carcinosarcoma

Cont .. : 

Cont .. D. Miscellaneous     1. Lymphoma, sarcoma    2. Squamous cell epidermoid carcinoma    3. Fibrosarcoma    4. Mucoepithelial carcinoma    5. Metastatic tumor

Iodine131 Scan : 

Iodine131 Scan Evaluation of retrosternal thyroid extention. Evaluation of ectopic thyroid tissue ( stroma ovari) Follow up for patients with differentiated thyroid cancer for remnants of thyroid tissue, recurrence and metastasis.

Slide 52: 

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