Fat fraction estimation of morphologically normal lumbar vertebrae using the two-point mDixon turbo spin-echo MRI with flexible echo times and multipeak spectral model of fat: Comparison between cancer and non-cancer patients

Purpose: This study aims to compare fat fraction of lumbar vertebrae between cancer and non-cancer patients, using the two-point modified Dixon (mDixon) turbo spin-echo (TSE) MRI with flexible echo times and multipeak fat spectral model. Materials and methods: Fat fraction was calculated from fat and water images reconstructed by the mDixon TSE technique. Fat fraction of fat-water phantoms measured with the mDixon TSE method was compared with actual fat percentages. Patients who had undergone mDixon spine MRI and dual-energy X-ray absorptiometry within one year and had no bone metastasis were divided into cancer (n = 7) and non-cancer (n = 23) groups. Fat fraction and bone mineral density (BMD) were compared between the two groups. Results: Fat fraction of phantoms measured with mDixon MRI was highly correlated with their actual fat percentages (P < 0.01, R² = 0.93). Fat fraction of lumbar vertebrae was significantly lower in cancer patients (58.27 ± 3.16%) than in non-cancer patients (70.48 ± 1.83%) (P < 0.01). BMD was not different between cancer (0.912 ± 0.057 g/cm²) and non-cancer patients (0.876 ± 0.032 g/cm²) (P = 0.58). Fat fraction and BMD showed no significant correlation (P = 0.95, R = 0.006). Conclusions: A two-point mDixon TSE method for assessing fat fraction was reliable. Fat fraction of morphologically normal lumbar vertebrae was significantly lower in cancer patients compared to non-cancer patients, using the two-point mDixon TSE technique.