Effect of time-of-flight technique on the diagnostic performance of 18F-FDG PET/CT for assessment of lymph node metastases in head and neck squamous cell carcinoma.

UNLABELLED Precise assessment of lymph node metastases is critical to the treatment outcome and overall survival of patients with head and neck squamous cell carcinoma (HNSCC). The purpose of this study was to investigate the effect of time-of-flight (TOF) technique on the diagnostic performance of (18)F-FDG PET/CT for assessment of lymph node metastases in HNSCC patients. METHODS In 39 patients with an initial diagnosis of HNSCC, preoperative staging (18)F-FDG PET/CT was performed to assess lymph node metastases before surgery and histologic verification. Potential lymph node metastases were evaluated and documented separately for the right and left neck in accordance with the head and neck lymph node level classification. Two experienced readers measured lesion volume and uptake for every PET-positive lymph node. Sensitivity, specificity, image quality, and the PET characterization of the lesion (benign or malignant) were compared between different reconstruction methods (TOF PET and standard high-definition PET) and matrices for both readers. RESULTS TOF PET significantly increased the maximal standardized uptake value (SUVmax) but had no significant effect on lesion volume. However, a higher SUVmax did not result in a significant increase in small-lesion detection. Sensitivity and image quality were slightly improved with TOF PET but not significantly so. Matrix, on the other hand, had a significant effect on detected lesion numbers, sensitivity, and image quality. CONCLUSION For preoperative assessment of lymph node metastases in HNSCC, (18)F-FDG PET/CT using TOF technique increases SUVmax in lesions and improves image quality but has no significant impact on small-lesion detectability.