Vertebral marrow fat content and diffusion indexes in postmenopausal women with varying bone density: MR evaluation

Purpose/Introduction: To prospectively investigate the relationship among vertebral marrow fat content,marrow apparent diffusion coefficient(ADC),and bone mineral densities(BMD) documented with dual x-ray absorptiometry (DXA) in postmenopausal women. Subjects and Methods: Institutional study approval and informed consent were obtained. Sixty postmenopausal women (mean, 61.7±4.9 years;range, 55-76 years) were divided into normal bone density group(T>-1.0,20 cases), osteopenic group(T=-1.0~-2.5,20 cases), and osteoporotic group(T<-2.5,20 cases) based on T score after DXA examination. Proton magnetic resonance spectroscopy (1H MRS) and diffusion-weighted MR imaging of the L3 vertebral body were performed with a 1.5-T whole-body MR imaging system. Marrow fat content and apparent diffusion coefficient (ADC) were compared among three bone density groups. The correlation between BMD and marrow fat content or ADC were analysed. Results: Vertebral marrow fat content was significantly increased in osteoporotic group(59.1%±8.8,P=0.003)or osteopenic group(54% ±7.6,P=0.039) when compared with that of the normal bone density group(49% ± 9.1). The difference of that was also significant(P=0.045) between osteoporotic and osteopenic group. The ADC of vertebral marrow did not change with bone density. A mild significant negative correlation was observed between marrow fat content and T score(γ=-0.46, P<0.001). A negative correlation between vertebral marrow fat content and ADC was significant in the osteoporotic group (γ=-0.72,P=0.008),though it was slight in all postmenopausal women(γ=-0.25,P=0.03). No signifcant correlation was present between bone density and marrow ADC (γ=0.315,P=0.16). Discussion/Conclusion: The subjects with osteoporosis in postmenopausal women experienced a corresponding increase in vertebral marrow fat content as bone density decreased. MRS can be a compensative way for BMD determination. The bone marrow fat content may acts as a significant diagnostic indicator of bone weakening. MRS and DWI can noninvasively assess the physiological and pathological process of bone marrow in postmenopausal women with osteoporosis. DWI could not reflect the BMD change alone. References: [1] Damilakis J,Maris TG,Karantanas AH.An update on the assessment of osteoporosis using radiologic techniques.Eur Radiol,2007,6:1591-1602. [2]Fanucci E, Manenti G, Masala S,et al. Multiparameter characterisation of vertebral osteoporosis with 3-T MR. Radiol Med, 2007, 112:208-223. [3]Griffith JF,Yeung DKW,Antonio GE,et al.Vertebral marrow fat content and diffusion and perfusion indexes in women with varying bone density: MR evaluation.Radiology,2006,241:831-838. [4] Shen W, Chen J, Punyanitya M, et al. MRI-measured bone marrow adipose tissue is inversely related to DXA-measured bone mineral in Caucasian women. Osteoporos Int,2007,18:641-647