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The Thyroid Gland
&
Iodine-131 Ablation Treatments
Faradally A OLLITE
30th November 2001
The Thyroid Gland
( A General Introduction)
RIGHT LOBE
LEFT LOBE
WINDPIPE
Location:
At the base of the neck, just below the Adam’s Apple.
Each lobe of the thyroid lies on either side of the windpipe.
Function:
To make, store and release thyroid hormones into your blood.
Thyroid Hormones
The Thyroid gland produces the two main hormones
¾ Thyroxine (T3)
¾ Triodothyronine(T4)
The thyroid hormones regulate
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¾
¾
¾
¾
heart rate,
blood pressure,
body temperature,
the rate at which food is converted into energy (metabolism),
and affects the nervous system, muscles, and other organs.
Thyroid
Hormones
Thyroid Hormones
Hypothalamic-pituitary-thyroid feedback system
The amount of thyroid hormone in the body is adjusted by the
hypothalamic-pituitary-thyroid feedback system
¾ The Thyroid Gland
(Thyroid Hormone )
¾ The Pituitary Gland
(Thyroid-Stimulating Hormone, TSH)
TRH
Hypothalamus
Pituitary
TSH
Thyroid
¾ The Hypothalamus
(Thyroid-Releasing Hormone, TRH)
Thyroid
Hormones
Thyroid Diseases
(Hypothyroidism)
Hypothyroidism
Thyroid gland producing too little thyroid hormones
Causes:
Hashimoto’s thyroiditis or Iodine deficiency
Signs & Symptoms:
slow heartbeat, weight gain, tiredness amongst other symptoms
Treatment:
Thyroid hormone replacement therapy
(Levothyroxine sodium)
Mild Thyroid Failure
A mild form of hypothyroidism
(thyroid hormones level normal, but a high TSH level)
Thyroid Diseases
(Hyperthyroidism)
Hyperthyroidism
Thyroid gland producing too much thyroid hormones
Causes:
Grave’s disease or thyroid nodules
Signs & Symptoms:
fast heartbeat, nervousness, weight loss, among other symptoms
Treatment:
Anti-thyroid drugs, surgery, or radioactive iodine treatment
Mild (Subclinical) Hyperthyroidism
A mild form of hyperthyroidism
(thyroid hormones level normal, but a low TSH level)
Thyroid Diseases
(Thyroid Nodules)
Thyroid nodules
A thyroid nodule is a lump, growth or swelling located in the thyroid
gland.
Signs & Symptoms:
palpable neck mass,neck pain, swallowing and breathing difficulty
Treatment:
Treatment of thyroid nodules depends on the type of the nodules
present
Thyroid Cancer
Test for thyroid nodules
¾ Physical examination of the thyroid
¾ Blood tests (thyroid hormone and TSH levels)
¾ Thyroid imaging tests (thyroid scan)
¾ Thyroid biopsy
Thyroid nodules can be either benign or malignant.
Thyroid Cancer is when the nodules are found to be malignant
Thyroid Cancer
(Treatment)
The treatment of thyroid cancer depends on the type and stage
of the cancer.
The main types of treatment used are:
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¾
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Surgery
Radiation therapy
Hormone therapy
Chemotherapy
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The most effective form of initial cancer therapy is surgery.
¾
Also in most cases there is total thyroidectomy.
(i.e complete removal of the thyroid glands).
I-131 Ablation Treatment
Difficult to remove all the thyroid tissue when
performing thyroidectomy.
Thus after total thyroidectomy we usually have the
radioactive iodine ablation treatment to destroy any
residual thyroid tissues.
Usually a large dose of I-131 administered
in the patient (~100-200 mCi) and the patient
has to be hospitalised.
Iodine – 131
(Physical Data)
Emission
Energy
Intensity
Gamma
364 KeV
82%
Beta
606 KeV (Maximum)
192 KeV (Average)
89%
Physical Half Life: 8.05 days Biological Half Life: 138 days
Effective Half Life: 7.60 days
γ
β
Thyroid Iodine Uptake
Large thyroid uptake
10 – 25 %
for a typical thyroid
2–3%
for residual thyroid tissue
after a thyroidectomy
Elimination of I-131
I-131 leaves body through bodily fluids
(saliva, sweat, blood, urine, faeces)
In most patient the majority of the administered
radioactive iodine has been extracted after 48 hours.
A recent study estimates a median effective half life of
the administered radioactive iodine to be 14 hours,
with substantial variation.
I-131 Ablation treatment
(Exposure and Contamination Risk)
The thyroid dose is principally due to the I-131's short range
beta radiation.
The accompanying high energy penetrating gamma ray radiation
mostly escapes the patient producing unwanted radiation fields.
Exposure risk:
to anyone in close proximity to the patient
Contamination risk:
to anything in contact with bodily fluids of patient
Radiation Safety
(Precautions & Practices)
Special radiation safety precautions must be taken
(i) to minimize exposure risk to
¾ other patients
¾ hospital workers
¾ family & friends
(ii) to minimize the contamination risk
All the radiation safety precautions associated with the
management of I-131 patient before, during and after therapy
are in accordance with the ALARA principle.
ALARA
As
Low
As
Reasonably
Achievable
economic and social factors taken into account.
Minimizing Exposure
Without compromising patient care, all
personnel should follow the following basic
principles to minimize the radiation
exposure:
(i)
Minimize time spent with patients by
planning ahead and working efficiently
(ii)
Maximize distance by working as far from
patient as possible
Patient Accommodation
Patient is assigned to a private room with a private
bathroom and the patient is isolated to the room.
Preferably a room in an outside corner of the building
with the bed close to the outside wall.
Flooring should be an impermeable material which is
washable and easily decontaminated.
All necessary equipment, housekeeping supplies and
amenities for the duration of radioactive isolation
should be placed in the room prior to the therapy.
Room Preparation
To minimize the risk of contaminating
objects or areas, the room and furniture
is protected using plastic and absorbent
materials before the treatment is given
in areas likely to be contaminated.
Also the room is arrange in a manner to
minimize the exposure to the visitors
and to other patients,
Information to Patient
A verbal and written explanation of the therapy
help the patient understand the nature of the
treatment and its radiation risks both to the
patient and to other persons.
MUHC patient information sheet which gives
information regarding the I-131 ablation
treatment.
Administration of Treatment
Preplanning to minimize occupational
exposure
The pill container is opened under the
fume hood.
The I-131 is usually administered orally
in form of capsule.
Radiation warning sign clearly visible
on the door of the room
Information to Visitors
Specific restrictions relating to visitors should also
be posted outside the patient’s room
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No pregnant women or children
No eating or drinking in the room
Do not use the patient’s bathroom
Keep a reasonable distance from patient (~1-2 m)
Keep visit short (< 1 h)
Daily Procedures
(Contamination Survey)
Contamination survey of items (e.g. food trays, wastes, linen,
etc.) prior to release from room, by Radiation Protection
Services
Wastes are surveyed, sorted and cleared from the room.
9 Contaminated waste are kept for decay in storage
(radioactive label, activity, isotope, date)
9 Non-contaminated waste are treated as normal waste
Always wear impermeable protective gloves and slip-off shoe
covers during contamination survey
Radioactive Spill
Spillage of radioiodine or body fluids (via vomitus, incontinence,
excessive sweating) will result in contamination of the area.
In this case
– The Radiation Safety office should be informed of the spill immediately.
– No attempt to clean up the spill should be made by the patient or by the
nursing staff.
– All persons not involved in the spill should vacate the area immediately
and access to the area should be restricted.
– Those involved in the spill should be monitored for contamination
before leaving.
– Ensure that impermeable gloves and slip-off shoe covers are worn all
the time during spill clean-up operation and decontamination.
Daily Procedures
(Exposure Level Measurements)
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The exposure level measurements are taken at
the neck
the shoulder
1 metre from patient
2 metres from patient
the entrance of the room
This procedure is done just after the dose has been administered
and on a daily basis during the period of hospitalization.
MUHC Radiation Protection Follow Up Sheet
Criteria for Patient Release
Decision concerning the possible release of the patient is based
on the results of a radiation survey in the proximity of the patient.
Approximate Approximate
Residual
Radiation
Dose
Level
Without restrictions
@ 1 metre
(NCRP 37, 1970)
@ 2 metres
(GMA 4, 1993)
8 mCi (296 MBq)
1.8 mR/hr
With restrictions
30 mCi (1110 MBq)
6.75 mR/hr
Without restrictions
8.11 mCi (300 MBq)
0.4 mR/hr
With restrictions
29.7 mCi (1100 MBq)
1.6 mR/hr
Restrictions
(for released patients)
Patients released with restrictions are strongly recommended
to
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Avoid close contact with other persons
Flush toilet 2 or 3 times after use and wash hands thoroughly
Use separate linen, bath towels, etc.
Wash clothes separately
Also patients released without restrictions are also advised to
follow these restrictions.
Decommissioning Process
Protective covering is removed and treated as
radioactive waste
All wastes, linen is surveyed and disposed of
accordingly
Floor and furniture are surveyed for
contamination
Contaminated areas are decontaminated
according to CNSC regulations and internal
standards.
CNSC Regulations & Internal Standards
(for decontamination level)
From CNSC therapeutic nuclear medicine license for
the room decommissioning
Prior to decommissioning of the room the non-fixed
contamination for I-131 must not exceed 3 Bq/cm2
MUHC Decommissioning Policy
Wipe test results are less than 0.5 Bq/cm2
Decommissioning Process
Wipe tests are taken to monitor the
contamination level
Process is repeated until the room is
decontaminated according to regulations
Head nurse is informed, warning signs
removed when the room can be reopened to
normal use
Acknowledgements
¾ Dr Robert Corns
¾ Maureen McQueen
¾ Marylene Clavet
¾ Daniel Alu
¾ Jodi Powers
Thank you !!!