Fat fraction quantification of lumbar spine: comparison of T1-weighted two-point Dixon and single-voxel magnetic resonance spectroscopy in diagnosis of multiple myeloma

PURPOSE We aimed to investigate the value of T1-weighted two-point Dixon technique and single-voxel magnetic resonance spectroscopy (MRS) in diagnosis of multiple myeloma (MM) through quantifying fat content of vertebral marrow. METHODS A total of 30 MM patients and 30 healthy volunteers underwent T1-weighted two-point Dixon and single-voxel MRS imaging. The fat fraction map (FFM) was reconstructed from the Dixon images using the equation FFM = Lip/In, where Lip represents fat maps and In represents in-phase images. The fat fraction (FF) of MRS was calculated by using the integral area of Lip peak divided by the sum of integral area of Lip peak and water peak. RESULTS FF values measured by the Dixon technique and MRS were significantly decreased in MM patients (45.99%+/- 3.39% and 47.63%+/- 4.38%) compared with healthy controls (64.43%+/- 0.96% and 76.22%+/- 1.91%) (P < 0.001 with both methods). FF values measured by Dixon technique were significantly positively correlated to those measured by MRS in MM (r = 0.837, P < 0.001) and healthy control group (r = 0.735, P < 0.001), respectively. There was no significant difference between area under the curve (AUC) obtained by the Dixon technique (0.878 +/- 0.047; range, 0.785 to 0.971; optimal cutoff, 56.35 for healthy controls vs. MM) and MRS (0.883 +/- 0.047; range, 0.791 to 0.974; optimal cutoff, 61.00 for healthy controls vs. MM). The ability of Dixon technique to differentiate MM group from healthy controls was equivalent to single-voxel MRS. CONCLUSION Regarding detection of fat contents in vertebral bone, T1-weighted two-point Dixon technique exhibited equivalent performance to single-voxel MRS in the diagnosis of multiple myeloma. Moreover, two-point Dixon is a more convenient and stable technique for assessing bone marrow changes in MM patients than single-voxel MRS.