Dual-Energy CT Enhances Image Quality for Liver Metastases Without Increasing Detection

A recent retrospective study has evaluated the clinical performance of dual-energy CT (DECT) in imaging hypovascular liver metastases, focusing on image quality and diagnostic utility. Conducted at Niguarda Hospital in Milan, the study compared DECT reconstructions at different virtual monoenergetic imaging (VMI) energy levels—40, 70, and 100 keV—with conventional single-energy CT (SECT) acquired at 120 kVp.

The analysis included 45 patients with a total of 128 hypovascular liver metastases. Image quality was assessed using both objective metrics—signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)—and a subjective 5-point Likert scale for lesion conspicuity and overall image quality.

Results showed that VMI at 40 keV produced the highest SNR (median 5.08), significantly greater than that of conventional CT (median 3.90; p=0.001). Subjective image quality also peaked at 40 keV with a median Likert score of 5.0, compared to 3.0 for SECT. Despite these improvements in visual and signal clarity, the CNR values did not differ significantly across the evaluated reconstructions (p=0.42). Importantly, no additional liver metastases were identified on DECT compared to conventional CT across any reconstruction level.

Radiation exposure was also assessed. The median computed tomography dose index (CTDIvol) for DECT was 45.4 mGy, comparable to that of SECT at 45.39 mGy (p=0.688). The dose-length product (DLP) similarly showed no significant difference (DECT: 1522.11 mGy·cm; SECT: 1342.80 mGy·cm; p=0.091), indicating that DECT does not increase radiation burden when using current reconstruction protocols.

Contrast media administration remained within standard diagnostic parameters, with most patients receiving either 100 or 110 mL of iodinated contrast agent at 370 mgI/mL concentration.

Although the 40 keV VMI reconstructions demonstrated higher lesion conspicuity and were consistently rated higher in subjective assessments, these gains did not translate into improved diagnostic yield. No new metastases were detected using DECT that were not already visible with SECT. Thus, the study concludes that the primary contribution of DECT in this context is improved visualization rather than enhanced detection capability.

The study’s limitations include its retrospective, single-center design and reliance on a single expert reader for subjective evaluation. Additionally, only three VMI energy levels were analyzed, and inter-reader variability was not assessed.

In summary, DECT with low-keV VMI reconstructions improves image clarity and lesion conspicuity in hypovascular liver metastases but does not result in additional lesion detection compared to conventional CT. Radiation exposure remains equivalent between DECT and SECT. The findings suggest that while DECT may aid interpretation, its impact on diagnostic outcomes in this setting is limited.