Evaluation of dual energy spectral CT in differentiating metastatic from non-metastatic lymph nodes in rectal cancer: Initial experience

Objectives To investigate the value of dual energy spectral CT (DEsCT) imaging in differentiating metastatic from non-metastatic lymph nodes in rectal cancer. Methods Fifty-five patients with rectal cancer underwent the arterial phase (AP) and portal venous phase (PP) contrast-enhanced DEsCT imaging. The virtual monochromatic images and iodine-based material decomposition images derived from DEsCT imaging were interpreted for lymph nodes (LNs) measurement. The short axis diameter and the normalized iodine concentration (nIC) of metastatic and non-metastatic LNs were measured. The two-sample t test was used to compare the short axis diameters and nIC values of metastatic and non-metastatic LNs. ROC analysis was performed to assess the diagnostic performance. Results One hundred and fifty two LNs including 92 non-metastatic LNs and 60 metastatic LNs were matched using the radiological-pathological correlation. The mean short axis diameter of metastatic LNs was significantly larger than that of the non-metastatic LNs (7.28 ± 2.28 mm vs. 4.90 ± 1.64 mm, P < 0.001). The mean nIC value for metastatic LNs was significantly lower than that of non-metastatic LNs (0.24 ± 0.08 vs. 0.34 ± 0.21, P = 0.001 in AP; 0.47 ± 0.18 vs. 0.64 ± 0.17, P < 0.001 in PP). Combining nIC (PP) with the short axis diameter, the overall accuracy could be improved to 82.9%. Conclusions With the combination of nIC value in PP and conventional size criterion, dual energy spectral imaging may be used to differentiate metastatic from non-metastatic lymph nodes in rectal cancer.