The evaluation of the usefulness of dual-energy computed tomography in the preoperative diagnosis of cervical lymph node metastases in oral squamous cell carcinoma

Objective: To evaluate useful parameters for differentiating metastatic lymph nodes in oral squamous cell carcinoma using dual-energy computed tomography (DECT) in the venous phase. Methods: A total of 117 lymph nodes without visually obvious necrosis (83 non-metastatic and 34 metastatic) from 40 patients were retrospectively analyzed. The region of interest was defined at the area with the maximum short diameter. Nine parameters were calculated and correlated with the pathology images: CT values of virtual monochromatic X-ray images at 40, 70, and 100 keV (HU_{40 keV}, HU_{70 keV}, HU_{100 keV}), iodine concentration (IC), CT value variation at 40–70 keV (λ_{40–70 HU}), 40–100 keV (λ_{40–100 HU}), lymph node long diameter, short diameter, and long-short diameter ratio. Results: Metastatic lymph nodes had lower CT and IC values than non-metastatic nodes. However, the short diameter had the highest the area under the receiver operating characteristic curve (AUC) with 0.846 (95 % confidence interval: 0.741–0.914), and the respective sensitivity and specificity were 82.4 % and 84.3 % at a cutoff of 7.54 mm. For parameters using CT values and IC, HU_{100 keV} had the highest AUC (0.737), followed by HU_{70 keV} (0.717), HU_{40 keV} (0.686), IC (0.660), λ_{40–100 HU} (0.659), and λ_{40–70 HU} (0.659). Six DECT-derived parameters showed the significant negative correlation to the short axis length. Conclusion: In the venous phase, although the significant differences were found in the DECT-derived parameters, the maximal short diameter was found to be the most useful parameter for the differentiation of metastatic lymph nodes.