All FDG-PET/CT data obtained from the designated facility were used in this study. Patients with blood glucose values of more than 150 mg/dL during PET/CT imaging were excluded. All patients were assessed using a Biograph PET/CT scanner (Siemens Healthcare, Erlangen, Germany). Unenhanced CT images of sections 2 to 4 mm thick that matched the PET images were acquired for each patient using a standard protocol. Immediately after the CT, PET covering the identical axial field of view for 2 to 4 min per table position depending on the condition of the patient and the scanner performance was conducted. SUVmax was established by drawing regions of interests (ROIs) on attenuation-corrected FDG-PET images, and calculated using the software integrated within the PET/CT scanner based on the following formula:
In which M is defined as the maximal activity at a single pixel within the tissue designated by the ROI, and ID is defined as the injected FDG dose/kg of body weight (w).
The preoperative FDG-PET/CT images were transferred to the Synapse Vincent 3D workstation (Fujifilm Corporation, Tokyo, Japan). LN-SUVmax was measured for each patient. ROIs were drawn and maximum FDG uptake in the lymph node was confirmed on CT.Figure 3 shows representative lymph node images of no. 7 lymph node (A), no. 4R lymph node (B), and no. 4L lymph node (C).
In which M is defined as the maximal activity at a single pixel within the tissue designated by the ROI, and ID is defined as the injected FDG dose/kg of body weight (w).
The preoperative FDG-PET/CT images were transferred to the Synapse Vincent 3D workstation (Fujifilm Corporation, Tokyo, Japan). LN-SUVmax was measured for each patient. ROIs were drawn and maximum FDG uptake in the lymph node was confirmed on CT.