Multimaterial decomposition algorithm for quantification of fat in hepatocellular carcinoma using rapid kilovoltage-switching dual-energy CT: A comparison with chemical-shift MR imaging

Understanding intratumoral fat in hepatocellular carcinoma (HCC) is clinically important to elucidate prognosis. We sought to quantify HCC and liver fat with a multimaterial decomposition (MMD) algorithm with rapid kilovoltage-switching dual-energy computed tomography (DECT) relative to chemical-shift magnetic resonance imaging (CSI). In this retrospective study, 40 consecutive patients with HCC underwent non-contrast-enhanced (non-CE) and four-phases contrast-enhanced (four-CE) DECT (80 and 140 kVp) and abdominal MR imaging (including CSI) between April 2011 and December 2012. Fat volume fraction (FVF(DECT)) maps were generated by MMD algorithm to quantify HCC and liver fat. Fat fraction measured by CSI (FF(CSI)) was determined for HCC and liver on dual-echo sequence using 1.5- or 3-Tesla MR systems. The correlation between FVF(DECT) and FF(CSI) was evaluated using Pearson correlation test, while non-CE FVF(DECT) and four-CE FVF(DECT) were compared by one-way ANOVA and Bland–Altman analysis. Forty patients (mean age, 70.1 years ± 7.8; 25 males) were evaluated. FVF(DECT) and FF(CSI) exhibited weak to moderate correlations for HCC in non-CE and four-CE except in equilibrium phase (r = 0.42, 0.44, 0.35, and 0.33; all P < .05), and very strong correlations for liver in all phases (r = 0.86, 0.83, 0.85, 0.87, and 0.84; all P < .05). Those correlation coefficients were significantly higher for liver for each phase (all P < .05). FVF(DECT) did not differ significantly across scan phases regarding HCC or liver (P = .076 and 0.56). Bland–Altman analysis showed fixed bias in all phases between non- and four-CE FVF(DECT) in HCC and liver. As compared with liver, correlations between FVF measured by DECT-based MMD and FF measured by CSI were weak in HCC in all phases. FVF is reproducible across all scan phases in HCC and liver. The MMD algorithm requires modification for HCC fat quantification given the heterogeneous components of HCC.