Download thyroid scintigraphy new 2011

DIAGNOSTIC IMAGING
THYROID SCINTIGRAPHY
Dr M G Nel(Riana)
INDEX
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Anatomy and cell structure
Physiology en Hormone production
The thyroid’s handling of iodine
Radionuclide imaging of the thyroid
Thyroid diseases to be imaged
hyper- en hypothyroidism
thyroid nodules
goiters
thyroiditis
thyroid ca
• Radio-active I-131 therapy for
Grave’s
Thyroid Ca
THYROID SCINTIGAPHY: KNOWLEDGE, UNDERSTANDING and
APPLICATION (LEVELS 1-3)  MUST KNOW the previously acquired
knowledge of the anatomy and physiology of the organs
OUTCOMES
ASSESSMENT CRITERIA
ASSESSMENT TASKS
Cell and Cell function imaging
Name and discuss basic principles of the
imagings (Technesium as well as Iodine)
Basic Interpretation and usage of
the RN procedures
The Basic information that you
can get from the thyroid imaging
Name and discuss the information
Basic Interpretation and usage of
the RN procedures
Normal thyroid scintigraphy
Interpretation of the normal images in order to
recognise any abnormalities
Basic Interpretation and usage of
the RN procedures
Radio nuclides in use for thyroid
imaging
Name, discuss and explain the usage of TcO4¯,
Tc-99m MIBI, I-123 and I131
Basic Interpretation and usage of
the RN procedures
Factors influencing the RN
uptake and distribution
Name, discuss and explain the development of
abnormalities
Basic Interpretation and usage of
the RN procedures
Abnormal thyroid images
Name, discuss and explain the development of
abnormalities
Interpretation of procedures and
study rapporting
Indications for thyroid
scintigraphy
Name and discuss the indications
Apply to patients and their
thyroid disease
Thyroid abnormalities to be
imaged
Name and discuss the imaging of the thyroid
abnormalities
Apply to patients and their
thyroid disease
Hyperthyroid diseases
Explain the abnormality and name the causes
Apply to patients and their
thyroid disease
Hypothyroid diseases
Explain the abnormality and name the causes
Apply to patients and their
thyroid disease
THYROID SCINTIGAPHY: KNOWLEDGE, UNDERSTANDING and
APPLICATION (LEVELS 1-3)  MUST KNOW the previously acquired
knowledge of the anatomy and physiology of the organs
OUTCOMES
ASSESSMENT CRITERIA
ASSESSMENT TASKS
Basic principles of the
Technesium thyroid scintigram
Explain the use of this procedure and all
the important precautions and
preparations
Apply to patients and their thyroid
disease
Basic principles of the 24h00
I-131 uptake procedure
Explain the use of this procedure and all
the important precautions and
preparations
Apply to patients and their thyroid
disease
Basic principles of the I-123
whole body imaging
Explain the use of this procedure and all
the important precautions and
preparations
Apply to patients and their thyroid
disease
Role of Tc-99m labelled MIBI in
thyroid imaging
Explain the use of this procedure
Apply to patients and their thyroid
disease
Non visualizing of the thyroid
Name and discuss the causes
Apply to patients and their thyroid
disease
Cold nodules in the thyroid
Describe how the lesions developes and
name the causes, what is the significance
of this type of lesions?
Basic Interpretation and usage of the
RN procedures and handling of
patients
Hot nodules in the thyroid
Name the causes and discuss the
further handling
Basic Interpretation and usage of the
RN procedures
Grave’s as a thyroid disease
Discuss the role of NM in the handling of
Grave’s patients (diagnostic/therapeutic)
Basic Interpretation and usage of the
RN procedures
Thyroiditis = acute and chronic
Discuss the role of NM in the handling of
the patients
Basic Interpretation and usage of the
RN procedures
Thyroid Cancers
Discuss the role of NM in the handling of
this patients
(Diagnostic/therapeutic/follow up)
Apply to patients and their thyroid
disease
THYROID SCINTIGAPHY: KNOWLEDGE, UNDERSTANDING and
APPLICATION (LEVELS 1-3)  MUST KNOW the previously acquired
knowledge of the anatomy and physiology of the organs
OUTCOMES
ASSESSMENT CRITERIA
ASSESSMENT TASKS
Goiters
Discuss the role of NM in the handling of
the patients
Apply to patients and their thyroid
disease
Multinodular thyroid /goiter
Explain the scintigraphic changes and
the importance of it
Apply to patients and their thyroid
disease
Role of pertechnitate in thyroid
scintigraphy
Name, discuss and explain the usage of
TcO4¯ in thyroid disease
Basic Interpretation and usage of
the RN procedures
Role of I-123 in thyroid imaging
Name, discuss and explain the usage of
I-123 in thyroid disease
Basic Interpretation and usage of
the RN procedures
Role of I-131 in thyroid imaging
and uptake countings
Name, discuss and explain the usage of
I-131 in thyroid disease
Basic Interpretation and usage of
the RN procedures
Role of I-131 in the therapeutic
role of NM
Name, discuss and explain the
therapeutic usage of I-131
Apply to patients and their thyroid
disease
The role of t ½ (half life time)in
the handling of thyroid
patients
Discuss and explain how it influences
the booking of radionuclide studies
Apply to patients and their thyroid
disease
RAI treatment for
hyperthyroidism
Discuss and explain the significance of
RAI treatment
Apply to patients and their thyroid
disease
Follow up of thyroid Cancer
patients in NM Department
Discuss NM role in the handling of the
patients
Apply to patients and their thyroid
disease
MACROSCOPIC ANATOMY
• 2 symmetrical lobes, united by an
isthmus of glandular tissue
• Placed in front of the 2-4th tracheal
rings
• Pre-tracheal fascia also present in this
region and are responsible for the
thyroid movement during swollowing
process
• PYRAMIDAL LOBE:a small portion of
gland tissue, projecting upwards from
the isthmus (just left to the midline),
representing a developmental residue
of the thyroglossal duct
MICROSCOPIC ANATOMY
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The thyroid consists of a mass
of follicular cells (98%)
Forms a mass of rounded
follicels/vesicels full with
colloid
A single layer of epithelial
cells/follicular cells forms the
walls of the follicles
The thyroid uses this iodine
containing product to store its
secretions
The sectretions contains the
Iodine hormone T3 en T4
Only 2% of the cells are parafollicular or C-cells which
secrete calcitonin.
C cells are present on the outer
aspects of the follicles
PHYSIOLOGY
THYROID HORMONE
PRODUCTION AND EXCRETION
IODINE HORMONE PRODUCTION
(FOLLICULAR CELL FUNCTION)
Two phases are involved for iodine uptake in the thyroid
to produce thyroxin
a)Iodine is TRAPPED in the thyroid
b)Iodine is ORGANIFIED in the hormone
Pathology can affect one or both of the above
Nuclear Medicine helps to differentiate between the two
IODINE HORMONE PRODUCTION:
• GIT  : uptake and absorption of dietary iodine (thyrosine)
• BLOOD  dietary intake of iodine as IODIDE = how much
iodide is there in the blood plasma? Active iodine pump
meganism for active uptake of I¯ in the cell in
• FOLLICULAR CELL EPITHELIAL WALL  : oxidation to
Iodine
• FOLLICULAR LUMEN*: Iodine + tyrosine = thyroid
Hormones MIT + DIT = T3
DIT + DIT = T4
T3 and T4 in thyroglobulin substans
• FOLLIKULERE EPITEEL WAND: pinocytosis, and
secretion of the thyroid hormones = T3 (free and bounded)
 T4 (pro H) bounded to TBG, into the blood.
• T4 (inactive) T3(active H): in liver, muscles and kidneys
• Active/free hormones diffuses into tissue and exerts its
metabolic action
T3 --------- 5%------
T4 ----- 95% ----
T3 = free /active H + TBG
T4 nonactive pro-H + TBG
T4 T3 in the liver /muscles and kidneys
THYROID HORMONE
REGULATING THE LEVELS
T3  5%  Free T3 + TBG = active hormone
T4  95% inactive T4 +TBG = pro H (mostly secreted)
T4  T3 (85%) in liver, muscles and kidneys
(CALCITONIN FROM the C CELLS)
NEGATIVE FEEDBACK
MEGANISM
HYPOTALAMUS
↓
TRH
↓
PITUITARY GLAND
↓
TSH
↓
THYROID
↓
T4 (T3) + TBG
T3
CIRCULATING THYROID HORMONES
↓
99% are bound to the plasma proteien (TBG)
thyroxine binding globulin
+
free hormones
BIOCHEMICAL MEASURING OF THE
THYIROID HORMONES
Measure both the free hormone levels as well as
the total concentration of the bounded
plasma hormone levels
LEVELS of BOUNDED
HORMONES
DEPEND ON THE LEVELS OF THE BINDING
PROTEIN/GLOBULINN (TBG)
INCREASED
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Pregnancy
Contraceptive pills
Estrogen therapy
Liver disease
Hyperthyroidism
DECREASED
Androgen
Nephrosis
THYROID’S HANDLING OF IODINE
PLASMA IODIDE POOL
FOLLICULAR
CELL WALLS
COLLOID
IN LUMEN
SIZE
How much iodide is
there in the blood
plasma?
I)Uptake of iodine from
GIT as iodide I¯
 iodided salt
UPTAKE/CONCENTRA
ORGANIFICATION
-TION/TRAPPING
Building into the thyroid
# the trapping
hormones
function does not
#organification defects
necessarily correlates Present with increased
with the biochemical
uptake with decreased
thyroid functions #
biochemical TF
 medications like
Corderone X
Kelp products, lugols
Contrast medium (CT)
Technesium is
handled in the same
way.
(Iodine and Tc-O4-)
Iodine on it’s own like in
I-131 uptake study
2) Endemic geographic
regions with
decreased levels of
iodine in the water and
ground
ELTROXIN is
blocking this function
Neomercazole is block
ing this function
IODINE UPTAKE ***
INCREASED
Hashimoto Thyroiditis
DECREASED
Virus thyroiditis
Hyperthyroidism
Due to Grave’s or Plummers
Hypothyroidism
primary or secondary to Iodine
contamination
Iodine deficiency due to increased/
rapid turnover and
Iodine setback
T4 administration
Like Eltroxin therapy
Nephrotic syndrome
Contras medium administration
during radiology examinations +
goiterogenic substances
Enzyme deficiency
Administration of Lugols or
Neomercazole
THYROID HORMONE FUNCTIONS
Metabolism of all body
cells
Secondary to this
metabolism
Protein catabolism
increased milk production
Carbohydrate absorpsion
Accelerate heart rate
Glucose combustion
acceleration
Lowers the pheripheral
resistance, hyperdynamic
blood circulation
Accelerate lipid synthesis
Stimulates the central nerve
systen, causing irritability
Stimulates growth and
development of the brain
function
Accelerate the need for
vitamins
RADIO-ISOTOPES USED IN
THYROID DISEASES
Diagnostic:
Pertegnitate
Tc-labelled MIBI
I-131 fluid and capsules
I-123
Therapeutic:
(Hyperthyroidism/Thyroid
Carcinomas)
I-131 fluid
TECHNESIUM - 99M
Tc-99M
PERTECHNETATE
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Used in Nuclear Medicine (NM) since1957 when the 99Mo-Tc-99M
GENERATOR was developed
86% off ALL THE NM studies are carried out with it! Is the most widely
used radionuclide for routine scanning
Cannot do more than one Tc-99m labelled studie/patient/day! Overlapping
of images take place.
Is constantly produced by the GENERATOR and is 24 hourly available!
IS CONCENTRATED/TAKEN UP or TRAPPED BUT NOT organified by
the thyroid follicle
The images is a reflection of the trapping properties/function of the thyroid
Very good physical character for imaging
T ½ = 6 h, with 140 KeV PHOTON ENERGY
Very good tissue penetration and imaging possibilities with the Gamma
Contains only GAMMA rays (no Beta rays)
Low absorbed radiation dosages
Distribution of plain Technesium:
*thyroid
*salivary glands
*stomach epithelium
TECHNESIUM THYROID SCINTIGRAM
INDICATIONS: Taken up, trapped or concentrated by the follicular
cell of the thyroid!
1. Evaluation of the – Thyroid’s Morphology and position
--Thyroid’s function in comparison to the salivary
glands (HYPER/HYPO)
2. Looking for ectopic thyroid tissue
3. Looking for residual thyroid tissue after thyroidectomy
4. Diagnosing the presence of thyroid nodules
PREPARATION:
• STOP Thyroid blocking MEDICATIONS like ELTROXIN and
NEOMERCAZOLE at least 3 weeks prior to the study
 IODINE containing medications like the CORDERONE
X , LUGOLS, KELP PRODUCTS, BETADINE
• Get the history of CT SCANNING with the administration of
CONTRAS MEDIUM OR ARTERIOGRAMMES IN the past 3
MONTHS
• PREVIOUS RAI Rx, CHIR/ HEAD + NECK XST
• STOP INGESTION of GOITEROGENIC FOODS like cabbage .
NORMAL THYROID SCAN
1. The presence of functioning thyroid tissue
2. Position of the thyroid
3. Size of the thyroid
4. Total uptake of RA
(in comparison to the salivary glands)
5. Presence of any nodules on the pinhole image
REQUIRE MOST RESENT BIOCHEMICAL
THYROID FUNCTIONS
THE EFFECT OF DISEASE ON CELLFUNCTIONS
COLD NODULES
HOT NODULES
NON-VISUALIZING of the
THYROID – REASONS?
EFFECT of CORDERONE X
MIBI THYROID SCAN
in patient using Corderone X
THE ROLE OF Tc-99M LABELLED MIBI
IN THYROID IMAGING
• MIBI is beter known as the MIOCARDIAL PERFUSION agent
(show similarities with 201 Tl)
• Meganisms of uptake into the thyroid cells are
 bloodflow
 cell membrane potential
 mitochondrial contents and function
• Used to image cold nodules in the thyroid, to confirm THE
PRESENCE OF THYROID TISSUE!
• Also used for Parathyroid adenoma imaging, due to the better and
lower background activity in comparison to that of 201 Tl
• RN mammography, detection of tumours of the brongus, thyroid and
brain.
• The delayed uptake after 2-3 hours increase the sensitivity of the
MIBI studies.
MIBI Wholebody scan
Technesium thyroid scan
23/10/07
Technesium thyroid scan
15/11/07
Normal R lobe
Probably enlarged
L lobe
Total uptake to
low
to evaluate
the thyroid’s Fx
MIBI thyroid = ONLY confirms the
Presence of thyrois tissue
NO Fx information
Massively enlarged
Left lobe with irregular
upake on the lat aspect
(confirmed with the sonar)
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Pertechnetate THYROID scan
THYROID IS ?? BLOCKED  non visualization of the thyroid
MIBI THYROID
CONFIRMS THE
UPTAKE MIBI IN THE
THYROID
NODULE
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Painfull thyroid mass, patient with possible
hyperthyroidism
Pertechnetate thyrois scan
No thyroid tissue present in the cold region
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TECHNESIUM THYROID
MIBI THYROID
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IODINE RADIO-ISOTOPES eg
I-131(reactor) and I-123(cyclotron)
IODINE 131:
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Halflife = 8.02 days, physical halflife long enough for therapy
the agent of choice for radio-active treatment of hyperthyroidism
and thyroid ca patients
Cheap radio-activity, readily available
Both gamma and B radiation that is being emitted
Medium energy BETA emission (0.61 MeV)
Beta particles causes ionizing effects by a path length of 1-2mm,
allowing local irradiation of eg thyroid gland tissue alone. Practically
no effects on the surrounding tissues
Also High energy GAMMA radiation , that results
in  poor images
 contributes to whole body radiation burden
 adds to radiation dose of staff and patient relatives
Is a Halogen that vapourates and contamination of the
atmosphere takes place during dispensing of the liquid form
(can be minimized by using the I-131 capsule)
THE ROLE OF I-131 IN THYROID
IMAGING AND TREATMENT
(A) 24H00 I-131 UPTAKE :
for the workout of BIOCHEMICALLY HYPERTIROIDISM PATIENTS
• NORMAL UPTAKE = 15-45%
• INCREASED I-131 UPTAKE = Iodine deficiency
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= Hyperthyroidism
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= Hashimoto Thyroiditis
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= Nephrotic syndrome
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= Enzyme deficiency
• DECREASED I-131 UPTAKE = Hypothyroidism
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= Eltroxin en Lugols Rx
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=Neomercazole Rx
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= Contras medium administration
during radiology examinations + goiterogenic substances
= IS BEING USED IN THE CALCULATIONS OF THE RAI Rx DOSAGES
• NEGATIVE PREGNANCY TESTS REQUIRED PRIOR TO
STATRING
GRAVE’S PATIENT’S WORKOUT
BEFORE RAI TREATMENT
FIRST: RA I-131 UPTAKE
THEN: TECHNESIUM THYROID SCAN
ALSO: THYROID FUNCTION RESULTS
NEG PREGNANCY TEST
FINALLY: RAI RX WITH I-131
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Tiroied teller / Thyroid counter
(B) RAI THERAPY: 2 TIPES
a) HYPERTHYROIDISM TREATMENT: 10-20 mCi orally
MAX EFFECT after 8-12 WEEKS
CAN ONLY REPEAT THIS Rx AGTER 3 MONTHS
COMPLICATIONS: RADIATION THYRODITIS
HYPERTHYROIDITIS DIRECTLY POST
TREATMENT (treated with INDERAL)
HYPOTHYROIDISM AFTER A FEW WEEKS
(treated with Eltroxin)
NO EVIDANCE OF THYROID CANCER DANGER
AFTER RAI Rx
b)THYROID CA PATIENTS = ABLATION DOSAGE
100-200 mCi
ISOLATION TREATMENT FOR 1 WEEK
RADIATION THYRODITIS
BEEN DONE AT RADIOTHERAPY AT NATIONAL HOSP
(C) I-131 WHOLEBODY IMAGING: FOLLOW UP OF THE THYROID Ca
PATIENTS if the I-123 IS NOT AVAILABLE
DONE POST THYROIDECTOMY,
STOP ELTROXIN 3 WEEKS PRIOR TO IMAGING,
RELATIVELY POOR IMAGES.
2mCi ORALLY ADMINISTRATED
IMAGING TAKES PLACE ON 24H AND 72H POST ADMINISTRATION
20 mCi RAI THERAPY
5 DAYS PRIOR TO THIS IMAGING
WAIT 8-12 WEEKS (3 MONTHS)
IODINE I-131
WHOLE BODY
RESIDUAL THYROID TISSUE
• IODINE 123:
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Iodine-123 (123I or I-123) is a radioactive isotope of iodine
used in nuclear medicine imaging (Best for imaging)
Iodine-123 is produced in a cyclotron by proton irradiation of
enriched xenon. (Very expensive), (Only Wednesdays available)
Its half-life is 13.22 hours;
the decay emits gamma radiation with predominant energies of
159 keV and 27 keV.
In medical applications, this radiation can be detected by a
gamma camera.
123I is the most suitable isotope of iodine for the diagnostic study
of thyroid diseases. 123I has other advantages for diagnostic imaging thyroid tissue and
thyroid cancer metastasis.[1] T
Stop Eltroxin 3 weeks prior To investigation 
it block’s thyroid and mets!
ROLE OF I-123 IN THE THYROID
A.
NON VISUALIZING OF THE THYROID
B. FOLLOW UP OF THYROID CA PATIENTS POST SURGERY AND
POST ABLATION TREATMENT
RESIDUAL THYROID TISSUE PRESENT
LUNGMETS
THYROID DISEASES
• EUTHYROIDISM: GOITERS
• HYPERTHYROIDISM
• HYPOTHYROIDSM
• THYROID NODULES
• THYROID CANCERS
• THYROIDITIS (akuut/chron)
• ECTOPIC THYROID TISSUE
EUTHYROIDISM and THYROID
DISEASES
• GOITERS
( = enlarged thyroid with NORMAL blood levels of TF)
CAUSES :
ENDEMIC GOITERS:
IODINE DEFICIENCY in ground and water
Especially the mountain regions of the EASTERN FS and LESOTHO
 ENOUGH DIETARY IODINE, BUT THYROID’S UPTAKE OF
IODINE IS BLOCKED BY CERTAIN MEDICATIONS
LIKE Metronidasool, tiosianaat, tio-urasiel
YOUNG WOMEN: (15-25years) assosiated with pregnancy
OLDER WOMEN: NODULAR GOITERS ( retro sternal )
BIOCHEMICALLY HYPOTHYRIODISM
OR EVEN EUTHYRIODISM
ORGANIFICATION DEFECT
MULTI-NODULAR GOITER
HYPERTHYROIDISM
• GRAVE’S (outo-immuun/antibody condition)
• NODULAR GOITERS  single nodule
 Plummer syndrome
 multi-nodular
• THYROIDITIS
sub acute viral/De Quervain
chronic OI thyroiditis/Hashimoto thyroiditis
Radiation thyroiditis
• EXOGENE IODINE CONTAMINATION
• TSH TYPE OF STIMULATION  chorio ca
pituatary tumour
testis tumour
TOXIC NODULES
PLUMMER’S
GRAVE’S DISEASE
CAUSES FOR HYPERTHYROIDISM :
• GRAVE’S DISEASE
• PLUMMER DISEASE autonomous functioning
thyroid lobes or nodules
• MULTI-NODULAR GOITERS
• VIRUS THYROIDITIS
• POST XST /RADIATION THYROIDITIS
• HASHIMOTO THYROIDITIS (only the early
stages)
• Exogene I- contamination (drinking iodine
containing medications bv corderone X)
• TSH STIMULATION by pituatary tumors / ovarian
chorio ca
HYPOTHYRIODISM CAUSES
• PRIMARY:
• SEKONDARY:
• THYROIDITIS:
Cretinism Primary hypothyroidism
idiopathic miksedoema
outo-immune failure
genetic enzyme defects
intake of goiterogenic substances
lithium, contras medium, corderone X
post surgery + post radiation
+ post RAI therapy
TSH deficiency
post partum
Hashimoto thyroiditis (chron)
• ENDEMIC IODINE DEFICIENCY: geografic/endemic
HYPOTHYROIDISM:
COLD NODULES
SINGLE COLD NODULES:
ADENOMATEUS HYPERPLASIA
COLLOID CYSTS
HEMATOMA
EXTERNAL PRESSURE ON THYROID
???THYROIDITIS
THYROID CA: 10 – 20% COULD BE MALIGNANT
3-4% DON’T TAKE UP Tc - 99M
CAN DO A I-123 SCINTIGRAM OR A MIBI SCAN****
NON-HOMOGENOUS UPTAKE:
MULTI-NODULAR THYROID
70% due to ADENOMATEUS HYPERPLASIA
FOLLICULAR ADENOMA
COLLOID CYSTS,
THYROI DITIS,
MULTI-NODULAR GOITER due to Iodine deficiency
30% due to THYROID CA after HEAD and NECK Radiation at RADIOTHERAPY
HASHIMOTO THYROIDITIS (OI DISEASE, TOTAL BURN OUT TAKE S PLACE )
PLUMMER ‘S DISEASE
POST SURGERY HYPERTHYROIDISM
THYROID CANCER
THYROID CARCINOMAS
• 95%  FOLLICULER HEMATOGEN
 PAPILLARY (80-90%)
LYMPHATIC spread , usually
young men, very good survival rate
• <5%  MEDULLARY (C-CELLS)
 ANAPLASTIC highly malignant,
older people, LOCAL PRESSURE Sx.
DO NOT TAKE UP IODINE
PAPILLARY
THYROID CA
FOLLICULAR THYROID CA
LONGMETS
ANAPLASTIC THYROID CA
MEDULARY THYROID CA
• Are not discussed in this lecture
• Develop from the C - cells
• Imaging Radionuclides are:
I-123 MIBG
Pentavalente DMSA
PET scans
“CSL” ACTIVITIES: ( PLAIN Tc-thyroid scintigram)
WHAT IS IMPORTANT ON GP LEVEL
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Technesium Thyroid Scintigram/Scan is a RN procedure without any side effects, can easily
been organized and done on an outpatient base
Call Nuclear Medicine Dept and make the booking to ensure availability of the radioactivities and
functionality of the gamma cameras. (051-4053487/8)
PATIENT IS THE SOURCE OF RADIATION BEWARE of patient contacts in Hospital
Commuter busses ( pregnant women and small children ) especially when going back home after
the thyroid scan and tests were done. They can drive with other people after diagnostic scan, but
make sure that they do not book a seat next to a pregnant woman or near small children. Correct
bookings is very important
Prepare the patients for the waiting periods for the RN scintigrams. The waiting period for plain
thyroid scan is 20 min with imaging time of half an hour, total duration of at least one hour after
getting the RA injection. After receiving the report of the thyroid scan patient can leave for
specialist clinic or go wait for rest of the patients at the Commuter transport busses
No need to keep patients without food or water from the previous evening. Can eat and drink
normally.
Important to stop all medications that can block the thyroids uptake of the radioactivity at
least 3 weeks prior to the scans. STOP Eltroxin, Celp products, Neomercazole, Corderone X,
AND report any contrasmedium investigation being done in previous 3 weeks.
Patient will be radio active for at least 24h00 after the thyroid scan
Don’t bring along any small children or pregnant family members
Don’t refer pregnant patient’s, make sure patient’s is not pregnant. Send along a most recent
negative pregnancy test and biochemical thyroid functions
In case of a lactating patient, the patient must milk out prior to the thyroid scans and arrange for
alternative feeding for the baby for the next 24 hours.
Only one RN study can be done on the same patient per day.
THERAPEUTIC FUNCTION
RAI THERAPY
IODINE RADIO-ISOTOPES
FOR THERAPEUTIC USE
• I-131 is the agent of choice, with both beta and
gamma rays that are being emitted. The beta rays
are responsible for the irradiation of the thyroid
tissue alone.
• With a half life of 8.02 days, the physical half life is
long enough for uptake and organification by the
follicular cells of the thyroid.
• It’s a relatively cheap radionuclide, readily available
and in the liquid form, oral administration is easy. It
is unfortunately a halogen that vapourises, and can
cause atmospheric and staff contamination. The
capsule form can minimize this risk.
HOW DOES THIS WORK??
• The RAI is administrated orally, and is absorbed rapidly from
the stomach. It quickly accumulates in the overactive thyroid
and is used in the synthesis of the thyroid hormones (in the
place of stable dietary iodine).
• It provokes an acute inflammatory response in the thyroid,
followed by cellular necrosis, atrophy and fibrosis with a
chronic inflammatory response.
• Loss of active thyroid gland tissue results in release of less
thyroid hormones.
• The thyroid size is reduced and hyperthyroidism is cured.
• The extent of this reaction depends on
•  amount of RAI taken up by the thyroid
• the radio-sensitivity of the thyroid.
FACTORS THAT INFLUENCE THE
EFFICACY OF THE RA I-131 DOSE
1) Functioning mass of overactive thyroid tissue
2) The presence of uniform or multi-nodular thyroid
tissue
3) % Uptake of I-131 as being calculated during the
diagnostic uptake study
4) Tempo of Iodine clearance from the thyroid (
influenced by exogenous factors such as intake of
iodine containing drugs, food and contrast medium
investigations
5)Radio-sensitivity of the thyroid
• All this must be taken in consideration when the
treatment dosage is determined.
AIM OF THE TREATMENT
• 1)To induce cellular hypofunction of the overactive
thyroid cells
• 2) To reduce hypersecretion of thyroid hormones
• 3) To achieve rapid improvement of the
hyperthyroidism
• 4) To restore the euthyroid state of the patient is
difficult ---it can be temporary, and be followed by
either hypo-or hyperthyroidism
• 5) Hypothyroidism remains the most likely result
and is considered to be the desired consequence.
COMPLICATIONS AND RISK
FACTORS
• Radiation thyroiditis
• Sialo-adenitis like parotitis
• Transient exacerbation of the hyperthyroiditis symptoms, this
can precipitate a thyroid crisis/storm in the elderly and patients
with co-existing cardiac or other medical illnesses
• Transient/Permanent Hypothyroidism that develops
progressively over 2-6 months. It is easily treated with eltroxin.
Regular S-TSH levels must be done.
• Hypo-parathyroidism, after treatment of post thyroidectomy
recurrence
• Worsening of the opthalmopathy
• Osteoperosis due to elevated levels of thyroid hormones and
calcitonin dysfunction after the RAI treatment
• Risk of residual/recurrent hyperthyroidism
DOSAGE AND MEASUREMENT UNITS
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1mCi radio-activity = 37 MBq (mega bequerals)
5mCi I-131 gives a radiation dose of the same magnitude as a common
radiological procedure similar to an IVP or Ba enema
1Gy = 100rads
1μCi deliveres 1 Rad of radiation to the thyroid
5mCi I-131 delivers 4000 Rads to the thyroid
The usual sufficient intra-thyroid absorbed dose of 150Gy (10mCi) is
syfficient to treat the hyperthyroid patient, but with relativly high
recurrence rates e.g.
46% after 60Gy and 14% after 150Gy.
In high risk patients a higher ablative dose of 300-400Gy (± 20mCi) is
necessary to establish an euthyroid state without the need for a
second RAI dose. For this ablative regime the incidence of
hypothyroidism is
86% after 3 months, and 93% after 18 months
RISKS OF THE RAI TREATMENT
• THE PATIENT
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Teratogenicity: Verify that the patient is NOT PREGNANT at the time
of treatment. A negative pregnancy test must be obtained before
starting the diagnostic procedures. Ensure adequate contraception
usage before patient is discharged after the treatment. Beware of large
radiation exposure after 10-12 weeks of pregnancy, because the fetus
thyroid starts to concentrate iodine and the thyroid can be damaged.
Genetic damage: If treated with RAI, it is recommended that the
patient DELAY any pregnancies for at least 6 months.
Carcinogenesis: No evidence was found that I-131 induced any
cancer, RAI treatment for Grave’s does not cause thyroid cancer.
Only patients who undergo head and neck irradiation have an
increased incidence of thyroid ca. A higher rate of thyroid adenomas
is found after RAI treatment to younger children.
•
Cell dysfunction: RAI treatment induces follicular thyroid cell
hypofunction after the initial radiation thyroiditis phase. ONLY the
hyperthyroidism is treated in Grave’s disease, NOT the immunological
disorder. There is then an increased risk for Grave’s opthalmopathic
effect and pre-tibial myxedoema. Anti thyroid drugs with their
immuno-suppressive effect could theoretically protect against
opthalmopathy.
• THE FAMILY AND GENERAL PUBLIC
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THE PATIENT IS THE RADIATION SOURCE !!!! AND CAN CAUSE A
RADIATION HAZARD .
The patient and his/her excretions (urine) is the source of radiation
after the RAI treatment. The radio active urine must be treated
carefully, and patients must not spill any urine. The tiolet must be
flushed 2 times and hands washed afterwards.
Patients must be informed beforehand of the radiation risk/hazard they
can cause after the treatment, and measures must be put in place to
reduce the radiation dose to healthy members of the public and their
families. Especially pregnant women and small children must be
avoided during the first 2 days post therapy
THERAPY PROCEDURE AND
INFORMED CONSENT
• Dietary Iodine is important in the synthesis of thyroid
hormones
• RA I-131 is administrated orally as therapy, and the follicular
thyroid cells incorporates this Iodine into it’s hormones. The
amount of Iodine in the RAI is very low and there is seldom any
adverse effects or complications. Patients can complain of
headache, sore throat or nausea after drinking the RAI fluid, but
it is only the probability of vomiting that causes concern, due
to the RA contamination hazard.
•
• The RAI dosage is prescribed by the Radiation Therapist. The
Medical Physicist assists the medical doctor to obtain the
correct dosage. The Iodine fluid must be handled carefully, and
due to its ability to vapourise, athmospheric contamination can
be prevented by using the I-131 capsules.
• Before administration, the patientmust be informed
orally and in writing of all the precautions and
radiation safety measurements . The informed
consent must be signed by the patient or by the
legal guardian of under aged children. Written
information are also given to ward personel and
families .
• Patients are asked to drink the RA fluid through a
straw, after which the physicist will measure the
radio-activity radiating from the patient to make sure
he/she is within the legal limits before discharge.
WHAT HAPPENS TO THE PATIENT
AFTER THE THERAPY WAS GIVEN??
• FOLLOW- UP AND ADJUVANT TREATMENT e.g. BBLOCKERS, ANTI-THYROID MEDICATION
– The maximum effect will only be seen 8-12 weeks posttreatment
– Follow–up blood investigation must be done 5 weeks posttreatment. Before 5 weeks the effect of the radiation
thyroiditis can be confusing due to worsening of the
hyperthyroid status.
– That’s why patients must continue to use their B-Blocker
therapy in this period.
– Hypothyroidism must be detected and treated.
– If the patient is still hyperthyroid 3 months post-treatment,
follow- up diagnostic procedures can only start after the 812 week waiting period.
• NB NB The follow up of these patients
are done by the referring doctors and
NOT by the Nuclear Medicine Clinic