Clinical Presentation

A 42-year-old woman with stage I papillary thyroid cancer presents for pre-therapy whole-body scan, ¹³¹I ablation therapy, and post-therapy whole-body scan. Her serum thyroglobulin level is markedly elevated at 300 ng/mL (normal, < 0.5 ng/mL).

Fig. 62.1 Whole-body parallel-hole collimator views, anterior and posterior projections, ¹²³I (pre-therapy, diagnostic dose).

Fig. 62.2 Whole-body parallel-hole collimator views, anterior and posterior projections, ¹³¹I (post-therapy dose).

Technique

• Pre-therapy scan: 2 mCi of oral ¹²³I 24 hours before scan

• Post-therapy scan: 200 mCi of oral ¹³¹I one week before scan

On the diagnostic (pre-therapy) ¹²³I scan, multiple small, scattered foci in the neck suggest remnant tissue and possibly regional nodal metastases. On the post-therapy scan, marked diffuse activity throughout the lungs and liver is new; the neck activity is much more intense and extensive.

Differential Diagnosis

• Metastatic thyroid carcinoma

• Salivary or urinary contamination

Diagnosis and Clinical Follow-Up

Thyroid remnant tissue, regional lymph node metastases, and diffuse pulmonary metastases; physiologic uptake of tracer in the liver on post-therapy scan. Diagnosis final.

Discussion