PMC5370468_01
Magnetic resonance T2-weighted imaging findings. (a) Postsurgical status: a recurrent lymph node metastasis from a papillary thyroid carcinoma in the right parapharyngeal space is shown (white arrow). (b) Three months after stereotactic radiation therapy (SRT) using the CyberKnife radiotherapy system, the lymph node metastasis is remarkably reduced. (c) Twelve months after SRT, the reduced lymph node metastasis has not changed. No recurrences were recognized, which indicates therapeutic effectiveness.
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fig1
A woman in her 60s presented with a recurrent lymph node metastasis in the right parapharyngeal space from a papillary thyroid carcinoma (Figure 1(a)).
(a) 18F-FDG PET/CT image: remarkable abnormal FDG uptake by the lymph node metastasis in the right parapharyngeal space. (b) 131I SPECT/CT image obtained 7 days after a 131I 3.7 GBq dose of RIT: 131I uptake by the lymph node metastasis is not evident. The abnormal distribution in the right maxillary sinus (white arrow) represents 131I secretion into the nasal fluid.
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fig2
At this time, highly abnormal 18F-fluorodeoxyglucose (FDG) uptake was detected in the right parapharyngeal space, which was diagnosed as a recurrent lymph node metastasis (Figure 2(a)). However, the lymph node metastasis did not take up the 131I (Figure 2(b)).
Dose distribution for the lymph node metastasis in the right parapharyngeal region. The planning target volume is illustrated by the thin orange line.
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fig3
The PTV was 4,790 mm3 (Figure 3).