Case Author(s): Thomas H. Vreeland, MD and Jerold Wallis, MD , 7/4/94 . Rating: #D2, #Q3

Diagnosis: No functioning thyroid tissue

Brief history:

Papillary CA of thyroid, rule out metastatic disease

Images:

Whole Body Imaging - I 131

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Full history/Diagnosis is available below

Diagnosis: No functioning thyroid tissue

Full history:

This patient is a 29 year old woman with a history of papillary carcinoma of the thyroid. The patient underwent total thyroidectomy and subsequent treatment with an ablative dose of I-131 (100 mCi) because of residual activity in the thyroid bed and adjacent lymph nodes. Today's study is obtained to determine if there is any remaining thyroid tissue.

Findings:

(1) Resolution of previously noted activity involving the focally increased activity involving the posterior cervical lymph node and left medial supraclavicular region.

(2) No evidence of new metastatic spread. No activity within the lungs is appreciated. Physiologic distribution of tracer activity is appreciated in the salivary glands; stomach; bladder; and, kidneys. Asymmetric salivary gland activity is seen, a reasonably common finding.

Discussion:

(1) Whole Body I-131 Imaging is utilized to detect metastatic spread of several thyroid cancers, including papillary, follicular, and mixed varieties. This imaging modality has limited use for Hurthle Cell Carcinoma. This modality is not useful for following anaplastic thyroid carcinoma or medullary carcinoma, since those tracers have only minimal I-131 avidity.

(2) The average dose used for diagnostic imaging at our institution is 5 mCi in adults The oral I-131 is swallowed on the first day of treatment; and delayed images are obtained 48 hours later. A large field of view camera calibrated for 364 kev with a 20% window and a high energy parallel hole collimator is used. Generally, images are collected for 100k or 10 minutes, whichever occurs first. Ocassionally, the patient may be imaged after an ablative dose of I-131 (eg, 100 mCi), with imaging typically 3-5 days after the treatment dose. Increased count rate may change the time of acquisition in the post treatment setting.

(3) I-123 can be used as an alternate imaging agent.

Followup:

The patient will be followed with imaging and thyroglobulin measurements. No further treatment is indicated at this time.

Major teaching point(s):

(1) Standard precautions for use of I-131 apply, such as no recent or current breastfeeding; avoiding prolonged contact with small children or family members for several days after treatment; good hygene, prompt flushing of the toilet after urination, etc.

(2) The patient's TSH should be adequately elevated (>20 microunits/ml) to insure good uptake by residual thyroid tissue and/or metastatic foci. This is typically done by withdrawal of thyroid hormone for 2-3 weeks, but can be done with administration of TSH (Thyrogen). Thyrogen is typically used only when prior withdrawal scans have been negative.

(3) The patient should have avoided iodine-containing mediciations (such as amiodarone, SSKI, IV contrast, Lugol's solution or other iodine-containing products) during 1-2 months prior to the examination. The effect of amiodarone can last 1-2 years.

(4) A nonpregnant state of all females within child-bearing age should be confirmed prior to I-131 dosing.

ACR Codes and Keywords:

References and General Discussion of Thyroid Scintigraphy (Anatomic field:Face, Mastoids, and Neck, Category:Neoplasm, Neoplastic-like condition)

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Case number: tr001

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