SPECT/Low dose ct detection of the unusual uptake of radioiodine in the rebound thymus after a repeated radioiodine treatment in the young woman with thyroid papillary carcinoma
Abstract
Aim: To present a rare case report about 31-year-old woman with the positive history papillary thyroid carcinoma and an uncommon rebound thymus uptake of 131I (radioiodine) on the post-therapy whole body scintigraphy and the chest SPECT/CT imaging after repeated radioiodine treatment. Method: The thyroid nodule was detected on ultrasound.
The papillary thyroid carcinoma was proven by fine needle aspiration biopsy. The woman underwent total thyroidectomy, repeated radioiodine treatments and post-therapy whole body scintigraphies and the chest SPECT/CT imaging.
The double-head SPECT/low dose CT multi-imaging scanner Infinia (GE) with infrared body contouring and the large field of view was used. The scanner was fitted with medium-energy, parallel-hole collimators.
Results: The whole body post-therapy scintigraphy and the chest SPECT/CT imaging after the second radioiodine treatment detected focal uptake of radioiodine in the mediastinum, which simulated thyroid cancer metastases. The subsequent SPECT/low dose CT revealed physiologic radioiodine uptake in the rebound thymus gland.
The repeated follow-up serum thyreoglobulin marker was negative and excluded metastases in the mediastinum. Conclusion: unusual radioiodine in rebound thymus can cause the false-positive whole body post-treatment scintigraphy and can lead to unnecessary surgery or the next radioiodine treatment.