Improved detection rates and treatment planning of head and neck cancer using dual-layer spectral CT.

PURPOSE: The aim of this study was to evaluate the advantages of dual-layer spectral CT (DLSCT) in detection and staging of head and neck cancer (HNC) as well as the imaging of tumour margins and infiltration depth compared to conventional contrast enhanced CT (CECT).

MATERIALS AND METHODS: Thirty-nine patients with a proven diagnosis of HNC were examined with a DLSCT scanner and retrospectively analysed. An age-matched healthy control group of the same size was used. Images were acquired in the venous phase. Virtual monoenergetic 40keV-equivalent (MonoE40) images were compared to CECT-images. Diagnostic confidence for tumour identification and margin detection was rated independently by four experienced observers. The steepness of the Hounsfield unit (HU)-increase at the tumour margin was analysed. External carotid artery branch image reconstructions were performed and their contrast compared to conventional arterial phase imaging. Means were compared using a Student's t-test. ANOVA was used for multiple comparisons.

RESULTS: MonoE40 images were superior to CECT-images in tumour detection and margin delineation. MonoE40 showed significantly higher attenuation differences between tumour and healthy tissue compared to CECT-images (p < 0.001). The HU-increase at the boundary of the tumour was significantly steeper in MonoE40 images compared to CECT-images (p < 0.001). Iodine uptake in the tumour was significantly higher compared to healthy tissue (p < 0.001). MonoE40 compared to conventional images allowed visualisation of external carotid artery branches from the venous phase in a higher number of cases (87% vs. 67%).

CONCLUSION: DLSCT enables improved detection of primary and recurrent head and neck cancer and quantification of tumour iodine uptake. Improved contrast of MonoE40 compared to conventional reconstructions enables higher diagnostic confidence concerning tumour margin detection and vessel identification.

KEY POINTS: • Sensitivity concerning tumour detection are higher using dual-layer spectral-CT than conventional CT. • Lesion to background contrast in DLSCT is significantly higher than in CECT. • DLSCT provides sufficient contrast for evaluation of external carotid artery branches.