FIGURE 6.  PET/CT for detection of recurrence. (A) Surveillance ¹⁸F-FDG PET/CT after therapy revealed prominent physiologic mandibular muscle uptake without evidence of recurrent disease. (B) Interval follow-up ¹⁸F-FDG PET/CT revealed new subtle hypermetabolic focus in left retropharyngeal region (red arrows) suspected of indicating recurrence. (C) T1-weighted contrast-enhanced MRI confirmed presence of suspect subcentimeter retropharyngeal lymph node (yellow arrow).