Noise characteristics of virtual monoenergetic images from a novel detector-based spectral CT scanner

Abstract Aim To evaluate the noise characteristics of virtual monoenergetic images (VMI) obtained from a recently introduced dual-layer detector-based spectral CT (SDCT), both in a phantom and patients. Materials and methods A cylindrical Catphan ® 600 phantom (The Phantom Library, Salem NY, USA) was scanned using the SDCT. Image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured in VMI from 40 to 200 keV as well as conventional 120 kVp images. One hundred consecutive patients who had an abdominal CT on the SDCT were then recruited in the study. Noise, SNR and CNR were measured in the liver, pancreas, spleen, kidney, abdominal aorta, portal vein, muscle, bone, and fat, both in VMI (40–200 keV) and conventional 120 kVp images. Qualitative image analysis was performed by an independent reader for vascular enhancement and image quality on a 5 point scale (1-worst, 5-best). Results On phantom studies, noise was low at all energies of VMI. Noise was highest at 40 keV (5.3 ± 0.2 HU), gradually decreased up to 70 keV (3.6 ± 0.2 HU), after which it remained constant up to 200 keV (3.5 ± 0.2 HU). In the patient cohort, noise was low ( Conclusion VMI obtained from the novel SDCT scanner have low noise across the entire spectrum of energies. There are significant SNR and CNR improvements compared to conventional 120 kVp images.