FIGURE 1. Planar images obtained 5 h after ¹²³I administration and before ¹³¹I therapy for thyroid remnant ablation. Mediastinal focus (arrow) detected on 5-h image (A) is not present on 24-h scan (B) or on scans after ¹³¹I therapy (not shown). Finding most likely represents focal retention of saliva ¹²³I in esophagus.