1H-MRS与DWI在骨质疏松症中的初步应用

Preliminary Application of MR Spectroscopy and MR Diffusion-weighted Imaging in Patients with Osteoporosis

目的探讨绝经后女性腰椎骨髓脂肪分数(fatfraction,FF)、表观扩散系数(apparent diffusion coefficient,ADC)值与骨密度(bone mineral densities,BMD)的关系。资料与方法将行腰椎双能量X线吸收测定(dual X-ray absorptionmetry,DXA)的60例绝经后女性根据T值分为3组:骨质正常组(T>-1.0)20例,骨质减少组(T=-1.0～-2.5)20例,骨质疏松组(T<-2.5)20例。所有研究对象均行氢质子磁共振波谱分析(1H MR spectroscopy,1H-MRS)、MR扩散加权成像(diffusion weighted imaging,DWI),分别测定L3椎体FF和ADC值。采用组间t检验对不同骨质组间FF、ADC值差异进行统计学分析。采用Pearson相关分析3组间FF、ADC值与BMD的相关性。结果骨质疏松组脂肪含量[(59.1±8.8)%,P=0.003]与骨质减少组脂肪含量[(54±7.6)%,P=0.039]均比骨质正常组[(49±9.1)%]高。骨质疏松组比骨质减少组椎体脂肪含量高(P=0.045)。椎体骨髓ADC值与T值无相关性。所有绝经后女性患者FF值与T值呈负相关(r=-0.46,P<0.01),与ADC值间呈轻度负相关(r=-0.25,P<0.05),但骨质疏松组中FF值与ADC值间呈较明显负相关(r=-0.72,P<0.01)。ADC值与T值无相关性(r=0.315,P>0.05)。结论绝经女性椎体骨髓脂肪含量随着BMD的减小而增大。MRS可作为BMD检查的辅助手段。MRS与DWI可以无创性了解骨质疏松症患者骨髓的生理、病理变化,单纯DWI并不能反映BMD的改变。

Objective 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. Materials and Methods Sixty postmenopausal women 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 （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 t test was used for comparisons between groups, and the Pearson test was used to determine correlation among marrow fat content, bone density and ADC. Resu- lts Vertebral marrow fat content was significantly increased in osteoporotic group （ 59.1% -＋ 8.8, P 〈 0.01 ） or osteopenic group（54% ＋ 7.6,P 〈 0.05 ） when compared with that of the normal bone density group （49% ＋ 9.1 ）. The difference of that was also significant （ P 〈 0.05 ） 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（ r = - 0.46, P 〈 0.01 ）. A negative correlation between vertebral marrow fat content and ADC was significant in the osteoporotic group （ r = - 0.72, P 〈 0.01 ）, though it was slight in all postmenopausal women （ r =- 0.25, P 〈 0.05 ）. No significant correlation was present between bone density and marrow ADC （r = 0. 315 ,P 〉 0.05 ）. 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. 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.