Purpose: Two-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). To develop a three-material decomposition-based bone marrow fat fraction (FF3MD) quantification technique using dual-energy CT, and investigate its feasibility to characterize osteoporotic and pathologic spinal fractures in adults.
Methods: Bone 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 were compared to MRI fat fraction FF_(MRI) and conventional two-material-decomposition-based fat fraction FF_(2MD). Subsequently, FF(3MD) was applied in a retrospective case study including seven adults (four male and three female; average age: 60.4 y.o.; range: 23-89 y.o.) with 10 spinal fractures (six acute osteoporotic, two hemangiomas, and two metastases) imaged at the time of admission. Findings were compared to MRI or pathology.
Results: FF_(3MD) demonstrated an excellent correlation with FF_(MRI) (r=0.97, R2=0.96) in the phantom, significantly more accurate than FF_(2MD) when confounding bone minerals are present (50 mg/cm3: r=1.02, R2=0.95 vs. r=0.65, R2=0.79 (p<0.01); 100 mg/cm3: r=0.81, R2=0.47 vs. r=0.21, R2=0.21 (p<0.05)). The fat factions of the 6/6 acute osteoporotic fractures were significantly lower than the healthy anatomical counterparts (p=0.0377). The fat fractions of the 2/2 vertebral hemangiomas and the 2/2 metastatic lesions were increased and decreased, respectively, when compared to healthy anatomical counterparts. These findings correlated well with T1-/T2-weighted MRI or pathology findings.
Conclusion: FF_(3MD) accurately quantified bone marrow fat fraction, comparing with FFMRI, in the phantom. Three-material decomposition-based findings correlated well with MRI or pathology in the case study to characterize osteoporotic and pathologic fractures.
Funding Support, Disclosures, and Conflict of Interest: B Li, V Andreu-Arasa, C LeBedis, S Anderson received a research grant from GE Healthcare on dual-energy CT clinical applications.
Not Applicable / None Entered.