Thyroid Therapy: Ablation

  • Ablation of residual functioning thyroid carcinoma.
  • Ablation of residual functioning normal thyroid tissue after total or partial thyroidectomy
  • Pregnancy or Nursing.
  • Allergy to iodine.
  • Iodinated studies recently performed.
  • Patients taking thyroid medications or vitamins, or not on low iodine diet.
  • Patient likely to regurgitat the dose administered
Radiopharmaceutical information:
  • Radionuclide: Iodine -131
  • Radiopharmaceutical :I-131 as sodium iodide (liquid or capsule)
  • Adult dosing: I-131 administered dose = gram size of thyroid gland x 100-180 µCi/gm divided by24- hour % RAIU or 29.9mCi if primary tumor is less than 1.5cm. 30-300mCi for primary tumors bigger than 1.5cm
  • Pediatric dosing: I-131 administered dose = gram size of thyroid gland x 100-180 µCi/gm divided by
    24- hour % RAIU
  • Method of administration: Oral (PO) capsule, through straw from lead container for liquid.
  • Method of Localization: Active Transport. Organification by thyrois and remains trapped in follicular cells
  • Physical Half-life: 8.1 days

Patient Preparation:
  • Verify doctor's Orders.
  • Low- Iodine diet 1 week before therapy (point of body starvation for iodine).
  • No iodinated radiographic studies 3 weeks before therapy.
  • Patient must discontinue use of iodide-containing preparations, thyroid hormones, and other medications that could potentially affect the ability of thyroid tissue to accumulate iodide for a sufficient time before contemplated therapy for 2-4 weeks.
  • Female patients cannot be pregnant or nursing nor should they have plans to be until the therapy and follow-up studies are completed.

Equipment Used:
High energy collimator.

A specific dose amount will be calculated to treat the patient's residual thyroid tissue. The Radioactive iodine pill will be ordered from the pharmacy. The patient needs to be made aware of the dose amount and lifestyle restrictions as consulted by the radiologist to minimize the effects of radiation and exposure to others. The patient should follow these restrictions for 3 to 5 days. The patient should then be administered the radioactive pill by mouth.

Normal Uptake and common varients:
Insert an image of a normal scan. Describe the normal uptake, and any normal varients visualized.
  • Residual thyroid tissue and thyroid carcinoma tissue ablated. Patient treated with thyroid medication.
external image nuclear_image_Thyroid%20Cancer.jpg
Abnormal Uptake and causes:

external image 2002_10_17_14_37_46_706.JPGexternal image 2002_10_17_14_36_15_706.JPG

This patient had thyroidectomy and was being evaluated prior to I-131 ablation (image on left). Patient had a TSH of 90 and was given 125 mCi of I-131. 10 day post image (right) demonstrates a high amount of activity in the thyroid bed which should be non existent which could suggest residual thyroid.

external image tr006trf29.gif
Normal physiological excretion of I-131 is seen in the salivary glands, gastrointestinal tract, bladder and sweat glands. Normal perspiration of I-131 was excreted by the sweat glands which remained in the patients long braided hair from her head to her back. The hair is down on the left image, then tied up on the right.

Questions asked in Patient History:
List the common questions asked when taking a patient history for this specific procedure.
  • Do you have a history of adenocarcinoma?
  • Do you have a history or family history of cancer? Y/N
  • If so, what type and for how long?
  • Why does the physician suspect ectopic tissue?
  • Do you have a history of thyroid disease? Y/N
  • Are you presently taking any iodine-containing medications, thyroid hormones, or antithyroid drugs?
  • Have you had any surgery? If so, what type and when?
  • Do you have difficulty swallowing?
  • Do you have any tenderness or swelling in the neck?
  • Have you had any recent weight loss or gain?
  • Have you had any recent change in your appetite?
  • Have you recently experienced fevers?
  • have you had any recent change in your overall energy levels?
  • Have you had any thyroid therapy, chemotherapy or radiation therapy.
  • Are you taking Vitamins ?
  • Are you pregnant or nursing?
  • Have you had any tests using iodine or radigraphic contrast?
  • Have you had or do you planned any recent related US, CT, x-ray?
  • Do you have any recent lab work results?
Nuclear Medicine Technology: Procedures and Quick reference (2nd edition) -- Pete Shackett