Diagnostic accuracy of ultrasound, 18F-FDG-PET/CT, and fused 18F-FDG-PET-MR images with DWI for the detection of cervical lymph node metastases of HNSCC

This study aimed to compare F-18-fluorodesoxyglucose positron emission tomography/MRI (F-18-FDG-PET-MRI) fusion images, including diffusion-weighted imaging (DWI), F-18-FDG-PET/CT, and ultrasound (US) regarding their performance in nodal staging of patients with head and neck squamous cell carcinoma (HNSCC). Eighteen patients prospectively underwent ultrasound examination, F-18-FDG- PET/CT, and MRI before oral tumor resection and bilateral neck dissection. PET data sets were fused with contrast-enhanced T1-weighted MR images. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for nodal detection were calculated for all the imaging modalities. Furthermore, the accuracy of the correct N-staging was calculated for all methods. Detailed histopathology served as the standard of reference. The sensitivity, specificity, PPV, NPV, and accuracy for detection of lymph node metastases were 63, 99, 86, 96, and 95 % for ultrasound; 30, 97, 56, 92, and 90 % for F-18-FDG-PET/CT; 52, 96, 59, 94, and 91 % for F-18-FDG-PET-MRI; and 53, 97, 67, 95, and 92 % for F-18-FDG-PET-MRI plus DWI, respectively. There was no significant difference in the diagnostic accuracy for lymph node metastasis detection between F-18-FDG-PET-MRI and F-18-FDG-PET/CT (p = 0.839) and between F-18-FDG-PET-MRI plus DWI and F-18-FDG-PET/CT (p = 0.286), respectively. US was significantly more accurate than F-18-FDG-PET/CT (p = 0.009), whereas no significant difference was seen between F-18-FDG-PET-MRI and US (p = 0.223) or F-18-FDG-PET-MRI plus DWI and US (p = 0.115). The nodal stage was correctly rated by F-18-FDG-PET-MRI in eight patients, F-18-FDG-PET-MRI plus DWI in nine patients, US in 12 patients, and F-18-FDG-PET/CT in five out of 18 patients. Software-based fusion of F-18-FDG-PET-MRI and F-18-FDG-PET-MRI plus DWI may not increase nodal detection and N-staging performance in patients with oral malignancies compared to US and F-18-FDG-PET/CT. Surgical staging of cervical lymph nodes will not be replaced even by advanced imaging modalities in the near future.