Quantification of spinal bone marrow fat fraction using three-material decomposition technique on dual-energy CT: A phantom study

BackgroundTwo-material decomposition is insufficient to quantify the fat fraction of spinal bone marrow, which is comprised of a mixture of bone minerals, water, and yellow marrow (fat). PurposeTo develop an accurate three-material decomposition-based bone marrow fat fraction (FF3MD$F{F_{3MD}}$) quantification technique for dual-energy CT. MethodsBone marrow edema phantoms containing trabecular bone minerals, water, and fat were constructed using fat fractions and bone mineral density values matching those expected in healthy and edematous bone, and scanned on a commercial dual-energy CT. Fat quantified by FF3MD$F{F_{3MD}}$ were compared to MRI-based fat fraction (FFMRI$F{F_{MRI}}$) and conventional two-material-decomposition-based fat fraction (FF2MD$F{F_{2MD}}$) to evaluate its accuracy and dependency on various bone mineral densities. ResultsFF3MD$F{F_{3MD}}$ demonstrated an excellent correlation with FFMRI$F{F_{MRI}}\;$(r = 0.97, R-2 = 0.96) in the phantom, significantly more accurate than FF2MD when confounding bone minerals are present (50 mg/cm(3): r = 1.02, R-2 = 0.95 vs. r = 0.65, R-2 = 0.79 (p < 0.01); 100 mg/cm(3): r = 0.81, R-2 = 0.47 vs. r = 0.21, R-2 = 0.21 (p < 0.05)). ConclusionsFF3MD$F{F_{3MD}}$ accurately quantified bone marrow fat fraction, when compared with FFMRI$F{F_{MRI}}$, in the specially constructed bone marrow phantom.