Radioiodine therapy uses radioactive iodine to treat hyperthyroidism and thyroid cancer. Iodine concentrates in the thyroid gland where it delivers radiation to ablate residual or cancerous thyroid tissue. For therapy, patients prepare with a low iodine diet and medication withdrawal before receiving doses ranging from 5-200 mCi orally. Strict radiation safety precautions are required during and after treatment due to iodine excretion. Whole body imaging with 1-5 mCi I-131 or I-123 sodium iodide is performed 48-72 hours later to identify residual thyroid tissue or cancer metastases and guide further treatment. Sources of error include contamination, stunning from prior I-131 doses, and saliv

1. RADIOIODINE THERAPY

2. Where does iodine go in the body?
• A) bone
• B) lung
• C) heart
• D) thyroid

3. What does the word ablate mean?
• A) cure
• B) destroy
• C) help
• D) increase absorption

4. What is a reason for RN Therapy?
• A) ablate cancer
• B) palliative treatment
• C) used instead of chemotherapy
• D) used instead of radiation therapy

5. What is Radionuclide Therapy ?
• The use of a radionuclide, generally
as a liquid or suspension, to treat
and ablate tumors or;
• as a palliative agent to reduce pain in
patients who are considered
terminally ill.

6. I-131 Sodium Iodide Therapy
• Principle:
I-131 is concentrated and retained in thyroid tissue. The beta
(β-) emission of I-131 delivers localized radiation to the area
• Clinical Applications:
– Hyperthyroidism: the objective is to render the patient
euthyroid
– Thyroid carcinoma: the objective is to ablate (destroy)
residual thyroid tissue and
functioning metastases

7. http://www.thyroidmanager.org/Chapter21/figures/figure12.png

8. Therapy for Hyperthyroidism
• Amount of radioactivity to be administered is based
on size of gland and radioiodine uptake
(dosages may range from ~5- ~33 mCi)
• Patient preparation:
– Off thyroid medications
– Fasting
– Check for swallowing difficulty
– Remove dental appliances
– Pregnancy test

9. Instructions to patient regarding radiation safety
precautions:
- Review routes of radioiodine excretion
- Use own bathroom if possible
- Flush twice; wash hands thoroughly
- No intimate contact for 2 wks
- Don’t share eating utensils/towels
- Wash personal clothing separately
- Flush tissues; don’t throw in trash
- Avoid public places for 2 wks
- Avoid holding children; maintain distance from
others

10. Therapy for Thyroid Cancer
• Typical dosage: 50-200 mCi
• It may be necessary to place the patient in isolation.
NRC regulations require isolation if the estimated
radiation dose to a member of the public will exceed
500 mrem

11. • Patient preparation
– Same prep as for hyperthyroid therapy
– Instruct patient regarding isolation requirements (visitors,
urine, nursing care, other) or instructions for the home
and public places
– Prepare patient psychologically for isolation
• Isolation room preparations
– Paper flat surfaces, door knobs, etc.
– Post door to room
– Linens, eating utensils, trash

12. I-131 Therapy Room View

13. I-131 Therapy Door Handles
Door handle leaving patient room Door handle entering bathroom

14. I-131 Therapy Bathroom

15. I-131 Therapy Covered Chair
Patient Comments:
-“The tape on the chair would
never secure the covering to the
chair sufficiently.”
-“I kept borrowing tape from other
parts of the room to re-tape it but
is was still ineffective.”

16. I-131 Therapy Room
Disposable stethoscope & cuff
Plastic covered phone
TV remote on dining tray
Pt. Comment: “You could not hear or speak well through plastic covering-just used
cell phone instead.”

17. I-131 Therapy Biohazard Container
Patient Comments:
- “Had two biohazard containers one for trash
one for linens”
-“Supplied with several gowns,
bath linens and bed linens.”
-“Showered 3-4 times a day and used
new towels and changed into new gowns”
-“Food served on disposable trays and everything on tray was disposable so that
one could put it all in biohazard container when done”
-”If got normal trays, had to stack cups, trays, utensils in room.”
“Dietary people would knock on the door, hand (throw) the tray quickly at you
and rush off”

18. There is accumulation of I-131 in the neck, salivary glands, gastrointestinal tract, and bladder. Additionally, there is
subtle activity extending superiorly from atop the patients head in an unusual "fountain-like" fashion on the anterior
image. On the posterior view, there is activity in a broad distribution over the back of the head just superior to the
large focus in the neck.
http://gamma.wustl.edu/tr006te129.html

19. • Nursing personnel
– Whole body dosimetry
– No pregnant personnel
– Restrict bedside nursing
• Monitoring for release from isolation
– Don’t predict
– Monitor with ionization chamber
• Discharge instructions to patient
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20. Instructions to I131
Therapy Patients Prior to
Discharge
• Routes of iodine excretion
– Urine
– Perspiration
– Sputum/saliva
– Tears
• Avoidance of certain activities
– Prolonged personal contact – children, partner, etc.
– Sharing of eating utensils
– Sharing of linens
– Breast-feeding – should be suspended for at least 80
days
• Double flushing the toilet after use
• Frequent hand washing

21. Radiotherapy Concerns
• I131
Thyroid Ablation Patient = main concern
• I131
– can be excreted in all bodily fluids –
sweat, saliva, urine, tears.
• At normal room temperature it can go to
gas form into the room air.
• Inhalation of I131
gas can result in thyroid
uptake to anyone who is exposed to it.

22. General Dose Limits I131
Therapy
• Nurses – limited to ~ 50mRem/24 hours
• Visitors – limited to ~ 20mRem/24 hours
• Unrestricted Areas – limited to 2mRem/
hour
• Minors (under 18 Y/O) – generally not
allowed access unless Authorized User (AU)
approves.

23. TOTAL BODY IMAGING
WITH RADIOIODINE

24. Total Body Imaging with I-131 NaI Follow-
Up of Thyroid Cancer
Purpose:
1) To determine the presence/extent of
residual functioning thyroid tissue following
surgery/radioiodine therapy
2) To determine the presence/location of
functioning thyroid cancer (metastases)

25. Clinical Procedure
1) ID patient; verify physician’s order; review clinical
indication for imaging
2) Explain procedure to patient; obtain relevant
history

26. Relevant Medical History
• Patient’s compliance with
low iodine diet;
discontinuation of
medications
• TSH/thyroglobulin levels
• Thyroid surgery information
– extent, tumor pathology
• Results of other imaging
procedures
• Physical exam findings
• History of prior radioiodine
administration for imaging
or therapy
http://www.endoconsultants.com/Lab/3400_testsoftfunction.gif

27. Clinical Procedure (cont’d)
3) Patient preparation
- discontinue medications that affect concentration of
iodine or that contain iodine
- low iodine diet for 3-10 days prior to and during
imaging
- measure TSH level (should be > 30-50 mU/L)
- mild laxatives day before imaging
- review radiation safety precautions
- pregnancy test – to document pregnancy is not an issue
- lactation history

28. Clinical Procedure (cont’d)
4) Administer 1-5 mCi I-131 or I-123 sodium iodide
orally
5) Image patient 48-72 hrs post tracer administration
- Anterior/posterior from top of head to mid-
thigh/knees; extremities/laterals/obliques as needed
- Use radioactive markers on anatomical landmarks

29. Sources of Error
• Contamination
– I-131 and I-123 sodium iodide are excreted in the urine,
saliva, and perspiration
- Protect self and equipment
- Take precautions to prevent contamination artifacts
on images
- Stunning - Stunning is best recognized 1 to 3 days after
therapeutic I-131

30. Top: diagnostic I-131; Bottom: little or no uptake of therapeutic I-131 because
the lesions were stunned by the diagnostic I-131
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31. Stunning is best recognized 1 to 3 days after therapeutic I-131. (A) A postoperative
diagnostic scan showing remnants. (B) ablative I-131 therapy was given 2 weeks later. 48
hr posttherapy scan shows no appreciable uptake. (C) a 7-day posttherapy scan shows
some of the cells in the stunned lesion can trap minimal amount of iodine if sufficient time
is allowed.

32. I-123 does not stun the thyroid.

33. I-123 whole body scan.
Salivary radioiodine in the esophagus: linear activity in the
midline chest is a possibility