Transcript Tc-99m MIBI scintigraphy

NUCLEAR
ENDOCRINOLOGY
Prof. Dr. Haluk B. Sayman
THYROİD Embryology
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Derived from median primordium which is
developed from two lateral primordia in 1st
maternal month.
It has two lobes connected with thyroglossal duct
and located in front of pharynx.
At the end of 7th week these lobes migrate to both
sides of trachea.
The lower part of thyroglossal duct makes
pyramidal lobe.
By the end of 3rd month it concentrates colloidal
material.
Within 10.5 weeks it concentrates iodine and
starts hormon synthesis.
THYROID Anatomy
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Thyroid consists of two lobes and an
isthmus connecting them. It is
located in front of neck at the level of
2. and 3. trachea cartilage.
It weighs 15-25 gr. Each lobe 4-4.5
cm in height and 2-2.5 cm in width,
isthmus is 2 cm wide and 0.5 cm
thick.
Superior thyroid arteries branches
from external carotis, inferior thyroid
arteries from the thyroservical
branch of subclavian artery. It has
superior, middle and inferior veins.
RecLN is close to inferior SupLN is
to superior arteries.
THYROID Physiology
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Thyroid gland produces T4 and T3 hormones in the
follicule cells after organifying the iodine trapped inside
the colloid by peroxidase and binding it with the
thyrosin molecule linked with thyroglobulin.
These hormones are released from the thyroglobulin
by proteolysis and secreted to the blood by TSH.
In the body, T4 is converted into T3 by 5´deiodinase
enzyme.
Calcitonin is secreted by parafollicular ‘C’ cells into the
serum depending on the calcium levels.
THYROID Diseases
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Thyroid diseases are very frequent in our
country and for the first diagnosis, in-vitro
laboratory tests with scintigraphy and
ultrasonography are used.
 Thyroid Diseases in general:
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Simple Goiter
Nodular Goiter
Hypothyroidism or Hyperthyroidism
Thyroiditis
Malignant Thyroid Diseases
In-vitro thyroid function tests
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T4, T3 or fT4, fT3: Lately radioimmunoassay, presently ELISA or
chemiluminescent methods are used to measure these. Increase
in hyperthyroidism, decrease in hypothyroidism or thyroiditis.
TSH: Increases or decreases by the negative feedback of thyroid
hormons on hypophysis. Increases in hypothyroidism, decreases
in hyperthyroidism.
Thyroglobulin: Helps to differentiate Thyrotoxicosis factitia and
thyrotoxicosis from thyroiditis. Actually, used in the follow-up of
well differentiated thyroid cancers after postoperative radioiodine
ablation. Increases in case of metastasis.
Calcitonin: Secreted by parafolicular C-cells. Used for the
diagnosis of C-cell hyperplasia or medullary thyroid carcinoma.
Pentagastrin or pentagastrin-Ca provocation increases its
sensitivity.
Thyroid antibodies: TT, TM, TPO, TSH receptor antibodies
increase in autoimmune thyroid diseases (Hashimoto, Graves’).
THYROID imaging
Radiography
 Scintigraphy-Planar, SPECT, PET
 Ultrasonography
 Computerized Tomography
 Magnetic Resonance Imaging
 X-ray Florescence scanning
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RADIOLOGY
Simple radiography can detect a space
occupying thyroid mass with incidental
calcifications.
 A chest X-ray, ordered for another
indication can show a soft tissue
density or a thyroid hyperplasia
shifting trachea off the midline.
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THYROID Scintigraphy
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Tc-99m pertechnetate is the most widely used
radionuclide.
 Tc-99m, is captured like iodine molecule but is not
organified. I-123, on the other hand, is both captured
and organified to show total function. But since it is a
cyclotron product, it is expensive and short lived.
 I-131 is usually spared for metastatic disease
screening for its high radiation dose and inferior image
quality.
 20 min. after iv injection of 5 mCi Tc-99m, anterior and
both anterior oblique images are acquired for 200.000
counts, preferably with pin-hole collimator.
 Sternal notch is marked with a radioactive marker.
THYROID Scintigraphy
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Both lobes are visualised as V-shaped elipsoid bodies
connected with a thin isthmus in normal scan.
 Salivary glands, oral mucosa and esophagus may be
seen in the neighbourhood.
 Right lobe is somewhat larger than the left.
 In 10% of the patients pyramidal lobe may be present.
ANTERIOR
R ANT. OBLİQUE
L ANT. OBLİQUE
THYROID Scintigraphy
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The size and activity uptake of thyroid
increase homogenously in hyperthyroidism
and Basedow Graves’ disease and pyramidal
lobe becomes prominent.
EXOPHTALMIA
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Normal
Enlarged
RAO
LAO
THYROID Scintigraphy
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The activity uptake decreases with variable
sizes in hypothyroidism and thyroiditis.
THYROID Scintigraphy
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Consuming external thyroid hormone,
iodine or radiological contrast media
decrease the uptake.
THYROID Scintigraphy
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While uptake increases
in a toxic nodule, it
decreases in the
surrounding tissue due
to suppression.
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Hypoactive nodules has
lower uptake in
comparison with its
surrounding and has an
increased malignancy
rate.
THYROID Scintigraphy
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In well differentiated thyroid cancers (DTC) Tl201 or Tc-99m MIBI uptake is more than
normal tissue.
 The recurrence and metastasis of DTC is
screened by periodical I-131 or I-123 wholebody scintigraphies.
 Medullary thyroid cancers may have I-131
MIBG, Tc-99m (V) DMSA or In-111 Octreotide
uptakes.
 Anaplastic and low differentiated cancers have
no Tc-99m or radioiodine uptakes.
THYROID Scintigraphy
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Normal Tc-99m MIBI
scintigraphy has
similarity with Tc99m and the uptake
decreases with time.
Tc-99m
MIBI 10 min.
MIBI 120 min.
THYROID Scintigraphy
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The MIBI uptake in malignant tumours with no Tc-99m
or I-131 uptake does not decrease with time.
Tc-99m
I-131
MIBI 10 dk.
MIBI 120 dk.
THYROID Scintigraphy
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Nodules without high malignancy risk does not have
Tc-99m MIBI uptake or have rapid washout.
MIBI 10 min.
MIBI 10 min.
MIBI 120 min.
MIBI 120 min.
Whole-body Scintigraphy
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An I-131 whole body
scan of a patient with
differentiated thyroid
cancer showing local
recurrence during
follow-up period,
after therapy.
ANTERIOR
POSTERIOR
Whole-body Scintigraphy
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I-131 negative but
In-111 octreotide
positive whole-body
scan in a patient with
metastatic Hurthle
cell thyroid cancer.
I-131
In-111 ocreotide
Anatomical Imaging Methods
CT
MRI
MRI
USG
Hybrid Imaging Methods
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The functional information is fuse with anatomical
detail by PET-CT or SPECT-CT. This helps more
precise lesion detection.
It is indicated in the follow-up of those thyroid cancer
patients with positive thyroglobulin levels but negative
I-131 WB scans.
X-ray FLORECENCE SCANING
Photons emited by Ameritium-241
source (γ ray) interact with the nonradioactive I-127 inside the thyroid cells
and produce X-rays to record on films.
 Favorable in small children and pregnant
ladies, since it does not need iv
radioactivity injections.
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THYROID Uptake Test
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A quantitative measure of thyroid function.
It gives a percentage uptake of a standart
radioiodine dose in a time constant.
Measurements are made at 4 and 24 hours.
It increases in hyperthyroidism, decreases in
hypothyroidism and thyroiditis.
Thyroid cpm (t)-Thigh cpm(t) Standart cpm(0)
Uptake %: ------------------------------------- x ---------------------- x 100
Standart cpm(t)
Glass cpm(0)
PARATHYROID Embryology
Lower parathyroid glands arise from III.
branchial sac, upper parathyroid glands
arise from IV. branchial sac.
 Upper glands are usually located behind
the upper poles of thyroid lobes.
 Although inferior glands are located
nearby lower poles, they have frequent
ectopic locations. Thymic or mediastinal
ectopies may be seen.
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PARATHYROID Anatomy and Physiology
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Normal parathyroid glands are 6 mm long, 3-4 mm
wide and 0.2-2 mm thick. There are 4 glands
They are perfused by inferior thyroid arteries or by
anastomoses between superior and inferior thyroid
arteries.
Parathyroid hormone regulates phosphate secretion
and calcium reabsorption in kidneys, stimulates
osteoclasts and increases calcium absorption in GIS.
Larynx
IV Parathyroids
III Parathyroids
PARATHYROID Diseases
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Hyperparathyroidism
Primary: The functional impairment of
parathyroids
 Secondary: The reaction of parathyroids to
chronic renal failure
 Tertiary: Autonomy of glands following
secondary hyperparathyroidism
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PARATHYROID Scintigraphy
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Technetium-Thallium subtraction scintigraphy:
Thyroid captures both Tc an Tl. Parathyroid
adenoma has only Tl uptake. First Tc-99m is
injected and imaged. Then without moving
patient under gamma camera Tl-201 is
injected and imaged again. Images acquired
on a computer are subtracted from each other
and discrepant parathyroid uptake is detected.
PARATHYROID Scintigraphy
Tc-99m MIBI scintigraphy: Used either
instead of Tl-201 in subtraction
scintigraphy or alone. If used alone, early
images showing focal radionuclide uptake
with retention on late images is
characteristic with parathyroid adenoma.
 Same condition is true also for mediastinal
ectopic glands. The retention of activity
indicates ectopic parathyroid adenoma.
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PARATHYROID Scintigraphy
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SPECT/CT: SPECT and
CT images are recorded
on the same equipment
simultaneously. CT
images are used for
attenuation correction
and detailed information
for sectional anatomy.
By this means the origin
of Tc-99m MIBI
accumulation is correctly
identified.
ADRENAL GLANDS
Adrenal Cortex scintigraphy:
I-131 labeled cholesterol is used to show
adrenal hyperplasia in Cushing
syndrome or primary aldosteronism.
 Adrenal Medullary scintigraphy: I-123 or
I-131 labeled MIBG
(metaiodobenzylguanidine) is used for
neuroblastoma ve pheochromacytoma.
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ADRENAL GLANDS
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I-131 MIBG uptake
on left adrenal
pheochromocytoma
mass.
ADRENAL GLANDS
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Neuroblastoma
AP
PA
ADRENAL GLANDS
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MRI and SPECT
slices showing I-123
MIBG uptake on
right adrenal
neuroblastoma and
its liver metastasis
 Low MIBG uptake in
the heart is related
with the increased
metabolism of
chatecholamins.
Therapy in Neuroendocrine Tumors
High dose I-131 MIBG is administered to
ablate MIBG receptor positive tumors.
 In-111 octreoscan is used to detect
receptor positivity to apply somatostatin
for treatment of carcinoid tumors.
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