Anatomical Variation of Age-Related Changes in Vertebral Bone Marrow Composition Using Chemical Shift Encoding-Based Water-Fat Magnetic Resonance Imaging

Assessment of vertebral bone marrow composition has been proposed as imaging biomarker for osteoporosis, hematopoietic, and metabolic disorders. We investigated the anatomical variation of age-related changes of vertebral proton density fat fraction (PDFF) using chemical shift encoding based water fat magnetic resonance imaging (MRI). 156 healthy subjects were recruited (age range 20-29 years: 12/30 males/females; 30-39: 15/9; 40-49: 4/14; 50-59: 9/27; 60-69: 5/19; 70-79: 4/8). An eight-echo 3D spoiled gradient-echo sequence at 31 MRI was used for chemical shift encoding based water fat separation at the lumbar spine. Vertebral bodies of L1-L4 were manually segmented to extract PDFF values at each vertebral level. PDFF averaged over L1-L4 was significantly (p < 0.05) higher in males than females in the twenties (32.0 +/- 8.0 vs. 27.2 +/- 6.0%) and thirties (35.3 +/- 6.7 vs. 27.3 +/- 6.2%). With increasing age, females showed an accelerated fatty conversion of the bone marrow compared to men with no significant (p > 0.05) mean PDFF differences in the forties (32.4 +/- 8.4 vs. 34.5 +/- 6.8%) and fifties (42.0 +/- 6.1 vs. 40.5 +/- 9.7%). The accelerated conversion process continued resulting in greater mean PDFF values in females than males in the sixties (40.2 +/- 6.9 vs. 48.8 +/- 7.7%; p = 0.033) and seventies (43.9 +/- 7.6 vs. 50.5 +/- 8.2%; p = 0.208), though the latter did not reach statistical significance. Relative age-related PDFF change from the twenties to the seventies increased from 16.7% (L1) to 51.4% (L4) in males and 76.8% (L1) to 85.7% (L4) in females. An accelerated fatty conversion of bone marrow was observed in females with increasing age particularly evident after menopause. Relative age-related PDFF changes showed an anatomical variation with most pronounced changes at lower lumbar vertebral levels in both sexes.