Spectral CT in patients with small HCC: investigation of image quality and diagnostic accuracy

Abstract

To assess image quality and diagnostic accuracy of monochromatic imaging from spectral CT in patients with small HCC (≤3cm). Twenty-seven patients with 31 HCC underwent spectral CT to generate conventional 140-kVp polychromatic images (group A) and monochromatic images with energy levels from 40 to 140keV (group B) during the late arterial phase (LAP) and the portal venous phase (PVP). Two-sample t tests compared the tumour-to-liver contrast-to-noise ratio (CNR) and mean image noise. Lesion detection for LAP, reader confidence and readers' subjective evaluations of image quality were recorded. Highest CNRs in group B were distributed at 40, 50 and 70keV. Higher CNR values and lesion conspicuity scores (LCS) were obtained in group B than in group A (CNR 3.36 ± 2.07 vs. 1.47 ± 0.89 in LAP; 2.29 ± 2.26 vs. 1.58 ± 1.75 in PVP; LCS 2.82, 2.84, 2.63 and 2.53 at 40-70keV, respectively, vs. 1.95) (P < 0.001). Lowest image noise for group B was at 70keV, resulting in higher image quality than that in group A (4.70 vs. 4.07; P < 0.001). Monochromatic energy levels of 40-70keV can increase detectability in small HCC and this increase might not result in image quality degradation. • Spectral computed tomography may help the detection of small hepatocellular carcinoma. • Monochromatic energy levels of 40-70keV increase the sensitivity for detection. • Prospective study showed that monochromatic imaging provides greater diagnostic confidence. • Monochromatic energy level of 70keV improves the overall image quality.