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Differentiating recurrent or residual nasopharyngeal carcinomas from post-radiotherapy changes with 18-fluoro-2-deoxyglucose positron emission tomography and thallium-201 single photon emission computed tomography in patients with indeterminate computed tomography findings.

The aim of this study was to compare the accuracy of 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) and thallium-201 (Tl-201) single photon emission computed tomography (SPECT) in differentiating recurrent/residual nasopharyngeal carcinomas (NPC) from post-radiotherapy (RT) changes in patients with indeterminate computed tomography (CT) findings. Twenty NPC patients with indeterminate CT findings were included at least 4 months after RT. CT, FDG-PET, Tl-201 SPECT and biopsy were performed within 1 week. The final diagnoses were based on biopsy findings and clinical follow-up for at least 6 months. For differentiating recurrent/residual NPC from post-RT changes in patients with indeterminate CT findings, the sensitivity, specificity and accuracy of FDG-PET were 100.0%, 92.3% and 96.0%, respectively. The sensitivity, specificity and accuracy of Tl-201 SPECT were 91.7%, 92.3% and 92.0%, respectively. Based on this study's findings, we can conclude FDG-PET is more sensitive but equally specific as Tl-201 SPECT is differentiating recurrent/residual NPC from post-RT changes in patients with indeterminate CT findings.