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Unformatted text preview: THYROID ISOTOPE
الدكتور قصي المقبل
أستاذ مشارك- قسم الشعة والطب
كلية الطب-جامعة العلوم والتكنولوجيا
الردنية Thyroid Diseases
Thyroid Thyrotoxicosis Hypothyroidism Thyroid nodules Thyrotoxicosis VS
Hyperthyroidism Thyrotoxicosis: a group of symptoms and
signs due to elevated thyroid hormones in
the body of any cause.
the Hyperthyroidism: a group of symptoms
and signs due to increased production of
thyroid hormones by hyper functioning
thyroid Causes of Thyrotoxicosis
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
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:
1- By mistake
12- with weight loss pills
2- Thyrotoxicosis and TFT
Thyrotoxicosis TSH is always suppressed in
thyrotoxicosis. TSH is the most sensitive test for thyroid
function and it is the screening test for
thyroid If TSH is abnormal, T3 and T4 levels can
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
elevated Based on TFT, the exact cause of
thyrotoxicosis can not be determined.
thyrotoxicosis Thyroid scan is a very helpful tool in
differentiating between various causes of
thyrotoxicosis. Thyroid scan and uptake
Thyroid Radioactive Iodine (RAI) is used for
thyroid scan and uptake.
thyroid RAI is given orally.
RAI Image and uptake are obtained after 24
hours Follicular cell traps Iodine and organifys it
to be incorporated with thyroid hormone.
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
special probe (uptake probe) just before
taking After 24 hours, measure photons in the
neck (thyroid gland).
neck Calculate % of photons concentrated in
thyroid gland. Thyroid Uptake Probe 24 hr Radioiodine Uptake
24 Example: 40% 24-hour RAI uptake means
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
(nodules). 24-hour RAI uptake is elevated, usually >
35% (mean of 40%).
35% Graves’ Disease
Graves’ Single Toxic Nodule
Single Single hot nodule (independent of TSH or
autonomous). Rest of thyroid gland is poorly visualized
due to low TSH level (TSH dependant).
due 24-hour RAI uptake is slightly elevated,
usually around 20%.
usually Toxic Nodule
Toxic Hot Nodule
Hot Toxic Multi-Nodular Goiter
Toxic Mild inhomogeneous uptake in thyroid
gland. Multiple cold and hot nodules in both
thyroid 24-hour uptake is mildly elevated, usually
between Multi-nodular Goiter
• Cut surface of one
lobe of thyroid gland
showing ill defined
• Focus of cystic
• Some hemorrhage
(red arrow) and
some Multi-nodular Goiter
Multi-nodular Early Phase Sub-acute
Thyroiditis Inhomogeneous uptake could be mild or
severe. In some cases thyroid gland is not
visualized. No significant focal abnormalities
(nodules). 24-hour RAI uptake is low, usually < 5%.
24-hour Sub-acute Thyroiditis
Hypothyroidism The main cause is chronic thyroiditis
(Hashimoto’s TSH is elevated. Thyroid scan does not have significant
diagnostic value in this entity.
diagnostic However, if there is nodule/nodules
confirmed by physical examination and
ultrasound, thyroid scan may be helpful.
Hypothyroidism Thyroid Nodules
Thyroid Nodules are usually found by physical
examination or by ultrasound.
examination The patient is usually euthyroid. Thyroid scan is helpful in characterizing
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
uptake. Thyroid scan can be done using free
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
of Toxic nodular goiter (single nodule or
multinodular) is ablated with 25-30 mCi of
I131 Ablation of Thyroid cancer with
I131 This is effective in differentiated thyroid
cancer Differentiated thyroid cancers are papillary
and follicular thyroid cancers.
and Both are originated from follicular cell
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)
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
cancer and anaplastic carcinoma.
Protocol Total thyroidectomy is required before
ablation. TSH should rise to more than 25 mlU\L. 100-200 mCi of I131 is needed for ablation
of remnant thyroid tissue post total
thyroidectomy. Radiation Protection
Radiation Cancer patients should be isolated in
special room (leaded walls) to prevent
others from radiation coming from the
patient. Isolation is usually for 2-3 days. Once the residual iodine is coming down
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
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This note was uploaded on 01/21/2012 for the course PDBIO 305 taught by Professor Woods,a during the Fall '08 term at BYU.
- Fall '08