Normal I 131 Whole body scan  (Prepared by Dr Gabriel Castro)

        41 y/o female, with papillary thyroid carcinoma. She underwent total thyroidectomy one month earlier. TSH pretreatment: 35.9 mlU/L . She followed a low iodine content diet for 7 days prior to I 131 administration (100 mCi). Post treatment whole body scan (WBS) in AP-PA views performed 7 days after administration of 100 mCi I 131. It shows physiologic I 131 uptake in salivary glands, liver, gastrointestinal tract and bladder. There is no evidence of functional thyroid tissue.

        To image patients with radioiodine in the follow up of differentiated thyroid carcinoma, TSH suppressive L- thyroxine therapy has to be withdrawn for several weeks to achieve a TSH of al least 30 mUI/l, and low iodine diet is recomended. Physiological sites of I 131 uptake include: salivary glands, oronasal mucosa, thymus gastrointestinal tract, liver, gallbladder, breast, uterus, bladder (1). Posttreatment scans can give new information that would alter the patient's prognosis. Posttherapy WBS has greater sensitivity than the diagnostic scan (2).

References:

1) Gambhir S, Ell P. Differentiated thyroid carcinoma. Nuclear Medicine in clinical diagnosis and treatment. 2004; Cap 12:154-156.

2) Sherman SI, et. Clinical utility of post-treatment radioiodine scans in the management of patients with thyroid cancer. J Clin Endocrinol Metab 1994; 78:629.

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