Evaluation of bone mineral density measurement of lumbar vertebrae by volumetric quantitative CT in postmenopausal women / 中华放射学杂志

ABSTRACT

Objective To demonstrate the validity of volumetric QCT and dual energy X-ray absorptiometry( DXA )in bone mineral density (BMD) measurement and compare the difference in discriminating osteoporotic postmenopansal women with and without vertebral fracture. Methods One hundred and eighteen postmenopausal women [ mean age (62. 1 ± 7.0) years ] who received thoracolumbar radiographic examination were enrolled and divided into four groups (normal, osteopenia, osteoporotic and osteoporotic fractured group) also based on their BMD value of lumbar vertebra(AP-SPINE) measured by DXA >x- 1s,x- 1s-x-2s, <x-2s without and with osteoporotic vertebral fracture. The second to four lumbar vertebrae were performed axial scan (for conventional 2D trabecular BMD measurement, 2D-TRAB by corresponding QCT software) and volumetric scan using MSCT. The volumetric data were transferred to the workstation ADW4. 2 for VR and MPR processing, and volumetric BMD were obtained based on the histogram of CT value, including integral BMD (3D-INTGL), cortical BMD (3D-CORT) and trabecular BMD (3D-TRAB), with the unit of mg/cm3. Apparent bone volume to total volume ratio ( App BV/TV% ) was calculated on the base of trabecular bone whose CT values were among 60 HU, 80 HU, 100 HU, 120--400 HU, respectively. Analysis of covariance (ANCOVA) and calculation of coefficient of determination ( R2 ) were performed for each parameter among the 4 groups. Results The values of 2D-TRAB, 3D- INT, 3D-TRAB, App60 BV/TV%, App80 BV/TV%, App100 BV/TV% and App120 BV/TV% in osteoporotic fractured group [(48.8±24.9) mg/cm3, (94.4±20.2) mg/cm3, (59.3±28.0) mg/cm3, (56. 1 ± 22. 8)%, (43.2±22. 2)%, (31.3±19. 4)%, (21.3±15. 6)% ] were significantly lower than those in osteoporotie group [ (74.9 ± 21.0) mg/cm3, ( 115.0 ± 14. 3 ) mg/cm3, (82. 0 ± 23.7) mg/cm3, (75.2 ± 16.8)%, (62.6 ± 20.5)%, (48.8 ± 21.7)%, (35.5 ± 20.1)%], osteopenia group [(89.2 ± 23.8) mg/cm3,(126.9 ± 12.9)mg/cm3, (97.8±25.2) mg/cm3, (85.1±13.7)%, (75. 1±17.9)%, (62.8±20.9)%, (49.2±21.9)%], and normal group[(120.6 ± 19.4) mg/cm3, (154.0 ± 16.3) mg/cm3, (131.1±21.1) mg/cm3, (95.6±5.3)%, (91.4±8.7)%, (84.7 ± 12.4)%, (75. 2 ± 15.5) % ], P <0. 01, respectively. For DXA parameter, there was no significant difference of AP-SPINE values found between osteoporotic fractured group [(0. 84±0. 16) g/cm2] and osteoporotic groups [ (0. 85±0. 06) g/cm2 ,P >0. 05 ]. In osteoporotic groups, AP-SPINE was not correlated significantly with other variables except 3D-CORT ( R2 = 0. 189, P < 0. 01 ) ; parameters of App60,80,100,120 BV/TV% were correlated significantly with 3 D-TRAB (R2 = 0. 955, 0. 951,0. 941,0. 912, P < 0. 01, respectively) and 2 D-TRAB(R2 = 0.912, 0.910, 0.878, 0.821, P < 0.01, respectively). The precision of 3D-BMD measurement was between 0. 70%--2. 25%. Conclusions Parameters derived from 3D-vQCT technique can discriminate osteoporotic postmenopausal women with fractured vertebrae from those without fractured vertebrae, and have better the capability than DXA. Among them, 3D-INTGL was the best parameter for diagnosing serious osteoporosis. App BV/TV% could be used to reflect the lost of trabecular bone precisely and to clinically predict fracture risk.