Evaluation Of Bone Mineral Density And Bone Quality In Osteoporotic Elderly Women With Multi-slice CT

Evaluating the changes of bone mass and bone quality in osteoporosis (OP) were considered as a correct method in the diagnosis and treatment of the disease. With the lumbar verterae and proximal femur BMD measurements of OP patients by volumetric QCT (vQCT) in multi-slice CT ( MSCT ) scanner, combining with the analysis of bone structure and biomechanical characterist, physicans can detect the effectiveness of the technique as the trace in assessing bone strength of OP patients. And all of these will be the evidences of providing clinically applicable method to the assessment of bone strength by imaging reseach.Part I Quantitative Study on Lumbar Vertebrae of Osteoporotic Elderly Women with MSCTPurpose To dertermine the identification of vertebral fracture by making several measurment of volumetric BMD values of osteoporotic elderly women with vQCT technique in MSCT scanner, the precision of these volumertic BMD indexes, and the threshold of the fracture value. To compare the bony structural conditions of lumbar vertebrae in osteoporotic elderly women with and without fracture.Materials and Methods MSCT spine scans of L₁ and L₂ (GE LightSpeed16, helical mode, 120kVp, 240mAs, 10mm beam width, 16 channels, pitch 1.375:1 ) were acquired in a cohort of 56 DXA (GE-Lunar DPX) diagnosed osteoporoticwomen, of whom 26 (mean age 67.8 ± 5.1 years) had radiographically confirmed atraumatic vertebral fractures belonged Group One and 30 (mean age 65.9 ± 5.4 years) were nonfractured contral subjects belonging Group Two. All the MSCT data of LI and L2 were retro-reconstructed into 1.25mm slice thickness and transferred to Sun Ultra80 Workstation and processed to measure single-slice trabecular and integral BMD (2D-TRAB> 2D-INTGL), and volumetric BMD (3D-INTGI^ 3D-CORI\ 3D-TRAB) in volume rendering (VR) images. BMD indexes in DXA were AP-SPINE and bone mineral apparent density (BMAD) in anteroposterior position.Ten elderly women (mean age 67.1 ± 5.1 years) were selected as the Normal Group in 2D-TRAB value in the normal range of documents and measured in the formal five indexes of BMD in twice MSCT scanning after repeatly positioning patients in order to calculate the precision of interscan measure. Also the 1.25mm axial reconstruction images of Li of the Normal Group were used to reformate 3D-VR images to analyse the bony structure of trabecula and calculate the ratio of bone volume to total volume (BV/TV) in the central volume as 2.0*2.0x2.0cm of Li vertebrae and to compare the indexes of ten patients randomly selected in 56 women in Group One and Group Two. ANOVA were used to evaluate the statistically significant when compare the differences of seven indexes between the Group One and Group Two. ROC curve (with SPSS Softwarell.5) was used to identify the different ability of 3D-INTGL and 3D-TRAB. Coefficients of determination for linear regressions were calculated between 2D-TRAB and 3D-TRAB> 2D-INTDL and 3D-INTGL or 3D-TNTGL and BMAD. The difference of values in BV/TV of Normal Group and 10 OP patients was compared by Student's t-test.Results AP-SPINE and BMAD measurements showed no statistically significant differences and all five volumetric BMD measurements showed statistically differences ( the decrements 18%²3%) between Group One and Group Two. Sensitivity, specificity and accuraty of identifying the difference between Group One and Group Two were 80.8%, 86.7% and 83.9% respectively, when the cut-off value of 3D-INTGL was 157.75mg/cm3 , and they were better than that of 3D-TRAB. Determination coefficients (r2) were 0.94,0.73 between 2D-TRAB and 3D-TRAB, 2D-INTGL and 3D-INTGL. The relationship between 3D-INTGL and BMAD showed no statistically significant. The value of BV/TV of Li vertebrae was 8.12% ± 1.96% in OP patients, significantly lower than the value 39.13% ± 2.15% of normal elderly women (p <0.01).Conclusion vQCT technique of lumbar vertebra in MSCT is superior than DXAin identifying the vertebral fracture in osteoporotic elderly women, and similar to DXA in measurement precision. So it will have the advantage in monitoring therapy efficacy. 3D image reformation by MSCT would detect the changes of vertebral structure in OP patients and thus improve the osteoporosis evaluation.Part II Quantitative Study on Proximal Femoral of Osteoporotic Elderly Women with MSCTPurpose To determine the differences of trabecula^ cortical and intergal bone mineral density (BMD) measurements obtained in the proximal femur by MSCT scans and vQCT technique in osteoporotic elderly women with and without fracture, and to assess the effect of vertebral fracture status on volumetric BMD of proximal femur.Materials and Methods The study population consisted of 56 women (all same as Part I). The three-dimensional MSCT (scanner and parameters same as Part I) images of left hip proximal femur were processed using ADW4.0 Workstation) to make measurements of left proximal femurs, including femoral neck trabecular/integral (N-TRAB ^ N-INTGL) , trochanteric trabecular/integral (T-TRAB > T-INTGL) , and total femur trabecular/cortical and integral (FEM-TRAB> FEM-CORT and FEM-INTGL) volumetric BMD, and hip axial length (HAL). Ten patients randomly selected in 56 women were measured in the formal seven indexes of BMD in twice MSCT scannings after repeatly positioning patients in order to calculate the precision of interscan measures. BMD measurements with DXA were also obtained in left femoral neck (NECK)> Wards triangle (WARDS) and trochanteric (TROCH) region. The differences of all 10 indexes between the subjects with and without vertebral fractures were analysed by ANOVA (SPSS 11.5).Results hi all the volumetric BMD indexes except the index of FEM-CORT, there were statistically significant differences (the decrements 14%¹8%) between Group One and Group Two, even after the correction of age and BMI, while values in DXA measurements had no statistically significant differences except WARDS after the correction of age and BMI. The decrement of T-TRAB between Group One and Group Two was 17.7%, more than of N-TRAB. Meanvalue of HAL of osteoporotic women was 9.84±0.91cm.Conclusion vQCT measurements by MSCT scan of proximal femur can be confirmed as a better technique in assessing the changes of proximal femoral BMD than DXA between osteoporotic elderly women with and without vertebral fracture independent on BMI and geometry of proximal femur.Part HI Finite Element Analysis in Lumbar Vertebrae of Osteoporotic Elderly WomenPropose To establish FE model from 3D-image by MSCT scanning of osteoporotic elderly women, and evaluate the stress distribution in osteoporotic lumbar vertebrae. To make clinical applicable evaluation of in vivo bone strength in osteoporotic vertebra of elderly women.Materials and Methods Li vertebrae of a osteoporotic female volunteer was scanned with MSCT (GE LightSpeed 16,120kVp, 240mAs, collimation of X-ray beam 0.625mm, DFOV320mm), and based on the reconstruction images (slice thickness 0.625mm ) of this patient , 3D finite element model of osteoporotic elderly women was established after using "computer carving" in Mimics software and divide element in ANSYS 7.0 in which bone material parameters were adopted according to the relation to physiological condition. Five patients in Group One and five patients in Group Two were randomly selected to make comparision of changes of stress strain after the physiological compressive, and the index of trabecular volume to total volume with compress strains above 5000 strain. The changes of the index were analysed by student's t-test.Results Stress level in cortical bone was relative higher than that of cancellous bone, and showed inhomogeneous at different site of lumbar vertebra. Stress values at middle level of vertebral trabecula were higher than other region as 11.6 MPa -15.4 MPa. Strain level at front margin and bilateral sites of middle cortical bone in 5 fractured women (0.035 strain, 0.078 strain and 0.086 strain) had increasing trend comparing the 5 non-fractured women, and the former group's percentage of the material with compressive strains above 5000 ^strain was 19.2% ±0.9%, significantly higher than later group 16.1%± 1.0% (P<0.01).Conclusion FE model of osteopototic elderly women was established successfully, and the stress and strain distributions throughtout the vertebral bodies were also analysis in the model. The trabecular volume where at risk of fracture material were higher in osteopototic fractured group than that in non-fractured group. FEA will have important clinical value in the in vivo elaluation of bone strength of osteoporotic patients.