Electron Density Dual-energy CT for Liver Metastasis Detection Compared with Conventional and Virtual Monoenergetic Images at 40 keV.

INTRODUCTION

To estimate the contrast-to-noise ratio (CNR) of liver metastases with electron density (ED) derived from dual-energy computed tomography and compare it with conventional and virtual monoenergetic images at 40 keV in both the unenhanced and portal-dominant phases.

METHODS

This observational retrospective, single-institution study included 32 patients with 49 liver metastases originating from digestive adenocarcinoma. All patients underwent dual-energy computed tomography (Spectral IQON®, Philips Healthcare) during unenhanced and portal-dominant phases. Conventional, virtual monoenergetic (VMI) images at 40 keV and ED images were reconstructed. The CNR of each metastasis was measured for each reconstruction in both the unenhanced and portal-dominant phases. Comparisons between techniques were conducted using linear mixed model regression.

RESULTS

Forty-nine liver metastases were included. For unenhanced acquisitions, ED demonstrated a statistically significantly higher CNR than both VMIs at 40 keV (mean difference 12.56 [95% IC, 10.17 to 14.95], p < 0.001) and conventional reconstructions (mean difference 12.83 [95% IC, 10.44 to 15.55], p < 0.001). Similarly, in the portal venous phase, ED showed a significantly higher CNR compared with both 40 keV monoenergetic (mean difference 9.81 [95% IC, 7.42 to 12.20], p < 0.001) and conventional reconstructions (mean difference 16.62 [95% IC, 14.23 to 19.00], p < 0.001). Moreover, a significantly better CNR was observed between unenhanced ED and portal venous 40 keV VMI (14.4626 ± 7.5 vs 11.1810 ± 6.2, respectively; p = 0.007).

DISCUSSION: Few studies have investigated electron density. These findings suggest that the CNR of liver metastases with ED is better than conventional and VMIs at 40 keV reconstructions, in both the unenhanced and portal-dominant phases. The single-center design and the small sample size limit the generalizability of these results.

CONCLUSION

Electron density provides a significantly better CNR for liver metastasis compared with both conventional and VMI at 40 keV reconstructions. Further studies are required to demonstrate that this gain in CNR improves the detection of hepatic metastases.