Abstract:

Objective To evaluate the diagnostic value of multiple parameters derived from Dual ⁃Layer Detector Spectral CT（DLSCT）in evaluating lymphatic metastasis（LM）in patients with rectal adenocarcinoma. Methods The data of 78 patients with rectal adenocarcinoma who underwent plain and dual⁃phase contrast⁃ enhanced scans by DLSCT before surgery were analyzed. According to the pathological findings，a total of 108 lymph nodes were enrolled and assigned to lymphatic metastasis（LM）group（n = 52）and non⁃lymphatic metastasis （NLM）group（n = 56）. The short diameter（SD），effective atomic number（Eff⁃Z）from plain scan，iodine con⁃ centration（IC）from arterial phase（AP），and venous phase（VP）were measured independently by two radiologists. The border，shape and enhancement homogeneity of each lymph node were evaluated. The normalized iodine con⁃ centration（NIC）in AP and VP were calculated. The differences of SD，border，shape，enhancement homogeneity， Eff⁃Z，NICAP，and NICVP were compared between the two groups by two independent samples Mann⁃Whitney test or Chi ⁃ square test. The diagnostic efficiencies were analyzed by receiver operating characteristic curves（ROC）. Results There were statistical differences in SD，border，shape，enhancement homogeneity，NICAP，and NICVP between LM and NLM group（all P ≤ 0.001. However，there was no significant difference in Eff⁃Z between the two groups（P > 0.05）. The areas under the curve（AUC）of SD，border，shape，enhancement homogeneity，NICAP， and NICVP to assess LM were 0.810，0.648，0.630，0.637，0.806，and 0.722，respectively（all P ≤ 0.05. The combination of the SD，NICAP and NICVP had the highest AUC value of 0.911，sensitivity of 80.77%，and speci⁃ ficity of 85.71%. Conclusion The NIC derived from DLSCT could significantly improve the diagnostic accuracy of LM of rectal adenocarcinoma. DLSCT parameters combined with SD are helpful to improve the diagnostic efficiency.

Key words:

rectal adenocarcinoma, lymphatic metastasis, spectral CT, iodine concentration, effective atomic number