To compare the differences of the spectral CT parameters between benign and malignant mediastina lymph nodes and to investigate the value of spectral imaging in the differential diagnosis.

According to the follow-up and pathology results, a total of 73 patients were enrolled in this study. One experienced radiologist determined the locations of lymph nodes on CT images corresponding to the surgical pathological ones. A total of 47 malignant nodes and 65 benign nodes were found. The longest and shortest diameters of lymph nodes in mediastina window were measured .The vHU, IC, WC, Z_eff and the CT values of normal lung, normal muscle and lymph nodes at 40, 70 and 140 keV were measured. The indices were compared between the benign nodes and malignant nodes by independent-samples t test. The Spectral HU curves were drawn.

The long and short diameter of malignant lymph nodes were (28.8±10.5), (20.3±9.1)cm , while they were were (14.0±4.6),(7.5±1.8)cm for benign lymph nodes. Malignant nodes were significantly larger than benign nodes (t=6.54, 7.13, respectively, P<0.05), The differences of the CT values at 40, 70 and 140 keV and the vHU, IC, WC, Z_eff for the normal lung, normal muscle and lymph nodes between the two groups had no statistical significance (P> 0.05). The two groups showed similar spectral HU curve slopes (1.86 values 1.73).

Spectral imaging may not be helpful in the differential diagnosis of malignant and benign lymph nodes.

Mediastinum; Lymph nodes; Tomography, X-ray computed; Diagnosis, differential