Value of Spectral Detector CT for Pretherapeutic, Locoregional Assessment of Esophageal Cancer

Purpose: To investigate the diagnostic value of spectral detector dual-energy CT-derived low-keV virtual monoenergetic images (VMI) and iodine overlays (IO) for locoregional, pretherapeutic assessment of esophageal cancer.

Method: 74 patients with biopsy-proven esophageal cancer who underwent pre-therapeutic, portal-venous-phase staging examinations of the chest and abdomen were retrospectively included. Quantitative image analysis was performed ROI-based within the tumor, healthy esophageal wall, peri-esophageal lymph nodes, azygos vein, aorta, liver, diaphragm, and mediastinal fat. Two radiologists evaluated delineation of the primary tumor and locoregional lymph nodes, assessment of the celiac trunk and diagnostic certainty regarding tumor infiltration in conventional images (CI), VMI from 40 to 70 keV and IO. Moreover, presence/absence of advanced tumor infiltration (T3/T4) was determined binary using all available images.

Results: VMI showed significantly higher attenuation and signal-to-noise ratio compared to CI for all assessed ROIs, peaking at VMI (p < 0.05). Contrast-to-noise ratio of tumor/esophagus (VMI/CI: 7.7 ± 4.7 vs. 2.3 ± 1.5), tumor/diaphragm (VMI/CI: 9.0 ± 5.5 vs. 2.2 ± 1.7) and tumor/liver (4.3 ± 5.5 vs. 1.9 ± 2.1) were all significantly higher compared to CI (p < 0.05). Qualitatively, lymph node delineation and diagnostic certainty regarding tumor infiltration received highest ratings both in IO and VMI, whereas vascular assessment was rated highest in VMI and primary tumor delineation in IO. Sensitivity/Specificity/Accuracy for detecting advanced tumor infiltration using the combination of CI, VMI and IO was 42.4 %/82.0 %/56.3 %.

Conclusions: IO and VMI improve qualitative assessment of the primary tumor and depiction of lymph nodes and vessels at pretherapeutic SDCT of esophageal cancer patients yet do not mitigate the limitations of CT in determining tumor infiltration.