Dual-layer spectral detector CT monoenergetic reconstruction improves image quality of non-contrast cerebral CT as compared with conventional single energy CT

Purpose: To investigate and compare image quality of monoenergetic reconstructions from spectral NCCT to conventional 120 kVp images acquired at a similar dose. Materials and methods: Patients undergoing NCCT on a dual-layer spectral detector CT (n=30) and a conventional CT (n= 30) were enrolled in the study. The spectral detector CT data was reconstructed at monoenergetic images from 40 to 140 keV in 5-keV increments and 65-70 keV in 1-keV increments (Group A1) and using single energy CT equivalent reconstruction (Group A2). The reference conventional 120kVp images (Group B) were acquired using a standard-of-care protocol with the same radiation dose. We evaluated the image quality of monoenergetic images and determined the optimal keV level using HU attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), artifact evaluation in posterior fossa by placing region-of-interest (ROI) and subjective image score by 2 radiologists independently using a 4-point scale (1-excellent, 4-undiagnostic). Results: The SNR and subjective image score were optimal at 66-70keV, while monoenergetic 68 keV images with a higher SNR (18.48 +/- 1.94, 15.55 +/- 1.56 and 14.33 +/- 1.38 for Group 68keV, A2 and B respectively, p < 0.001), CNR (4.09 +/- 0.65, 3.43 +/- 0.56 and 3.52 +/- 0.55 for Group 68keV, A2 and B respectively, p < 0.001) and a lower noise (1.80 +/- 0.19, 2.11 +/- 0.19 and 2.25 +/- 0.25 for Group 68keV, A2 and B respectively, p < 0.001). Conclusion: Spectral NCCT monoenergetic reconstructions at 68 keV improve image quality and reduce artifact compared to conventional single energy CT without radiation dose penalty.