Purpose: To use proton magnetic resonance spectroscopy ( 1 H-MRS) to evaluate vertebral marrow fat, and to determine whether bone density correlates with fat content and fat unsaturation levels in postmenopausal women.
Materials and Methods:Fifty-three women (mean age ϭ 70 years) underwent dual energy x-ray absorptiometry and 1 H-MRS, and 12 young female controls (mean age ϭ 28 years) underwent 1 H-MRS of the lumber spine. Water and lipid peak amplitudes were measured to calculate fat content and fat unsaturation index. Spearman's correlation tests and a t-test comparison of means were applied.
Results:1 H-MRS was successful in 15 normal, 15 osteopenic, and 20 osteoporotic subjects, and in all controls. Marrow fat content was significantly elevated in osteoporotic (65.5% Ϯ 10%) and osteopenic (63.5% Ϯ 9.3%) subjects compared to normal subjects (56.3% Ϯ 11.2%) and young controls (29% Ϯ 9.6%). The fat unsaturation index was significantly decreased in osteoporotic (0.091 Ϯ 0.013) and osteopenic (0.097 Ϯ 0.014) subjects compared to normal subjects (0.114 Ϯ 0.016) and young controls (0.127 Ϯ 0.031). A good inverse correlation was observed between the fat content and the unsaturation index (r s ϭ -0.53, P Ͻ 0.0001).
Conclusion:Osteoporosis is associated with increased marrow fat. As marrow fat increases, saturated lipids appear to increase preferentially to unsaturated lipids.
Subjects with osteoporosis have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with osteopenia. Similarly, subjects with osteopenia have decreased vertebral marrow perfusion and increased marrow fat compared with these parameters in subjects with normal bone density.
The subjects experienced a decrease in vertebral marrow maximum enhancement and enhancement slope and an increase in marrow fat content as bone density decreased. The reduction in perfusion indexes occurred only within the vertebral body and not in the paravertebral tissues supplied by the same artery.
Sonography is comparable to electrodiagnostic study in diagnosis of CTS and should be considered as initial test of choice for patients suspected of having CTS.
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