Comparison of 2D and 3D measured iodine concentration of gastric adenocarcinoma on spectral-CT and their relationship with perineural invasion

BACKGROUND: To determine the optimal region of interest (ROI) measurement strategy in spectral computed tomography (CT) for the preoperative prediction of perineural invasion (PNI) in gastric adenocarcinoma. METHODS: This retrospective study analyzed 91 gastric adenocarcinoma patients undergoing triple-phase (arterial, venous, and delayed phase; AP/VP/DP) contrast-enhanced spectral CT within two weeks before surgery. Patients were divided into PNI-positive and PNI-negative groups based on pathological findings. Iodine concentration (IC) values were measured using two free-hand ROI approaches: a two-dimensional ROI (2D-ROI) and a three-dimensional volumetric ROI (3D-ROI). Normalized IC (nIC) was also calculated. Consistency and correlation between the two ROI measurements were assessed. Differences in clinicopathological and CT features between the PNI-positive and PNI-negative groups were analyzed. The area under the receiver operating characteristic curve (AUC) was used to evaluate predictive performance. Logistic regression identified independent risk factors for PNI. RESULTS: The ICs measured by 2D and 3D-ROI showed excellent consistency (ICC = 0.803-0.853) and correlation (r = 0.777-0.797), though 2D-ROI yielded higher values (all P < 0.05). 2D-ICVP, 2D-ICDP, 2D-nICVP, 2D-nICDP and 3D-nICDP, were significantly higher in PNI-positive GC (P < 0.05). 2D-nICDP had the highest predictive AUC (0.761), outperforming other parameters (AUC = 0.622-0.670; P < 0.05). Multivariable analysis confirmed 2D-nICDP as the only independent PNI predictor. CONCLUSIONS: Although the consistency and correlation between 2D and 3D-ROIs were excellent, only 2D-nICDP was an independent predictor for PNI in gastric cancer (GC) and demonstrated superior predictive performance.