Physiologic Uptake of 131I in Uterus (Prepared by Dr Javiera Gonzalez)
Female patient, 38 year old. With diagnosis of thyroid papillary cancer treated with total thyroidectomy and referred to Nuclear Medicine for 150 mCi of radioiodine. TSH previous to dose of I131 was 44.4 uUI/L. After direct interrogation she refers starting her menstruation period the same day of the whole body scan with therapeutic I131 administration.
Whole body scan at the left hand side (I 131): shows evidence of a focus of mild uptake with poor defined edges in the middle third of the anterior neck region (small arrow). And also intense, rounded focus with defined borders on pelvic region of approximately 2 x 2 cm. (large arrow). In the rest of the body there was usual activity of the radiotracer in oronasal region, liver, gastrointestinal tract and bladder.
Spect with double window for 99mTc-MDP and 131I-Na was performed and seen at the right hand side. Upper image shows 99mTc-MDP saggital slice, being prominent the lumbo-sacrum spine and bladder (white arrow). Middle image depicts the same slice level and 131I-Na with yellow arrow pointing to the pelvic focus under evaluation. In the lower image, it can be seen the fusion of the 2 previous slices. Note that the focus is behind and superior to the bladder, in the uterus anatomical site.
References:
1
Charles W. Sutter. False-positive results of I-131 whole-body scans in patients
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2 Hirata K. Clin Nucl Med. 2009 Mar;34(3):180-1. Radioiodine therapy
for thyroid cancer depicted uterine leiomyoma.
3 Shapiro B. Artifacts, anatomical and physiological variants, and
unrelated diseases that might cause false-positive whole-body 131-I scans in
patients with thyroid cancer. Semin Nucl Med. 2000 Apr;30(2):115-32.