Implementation and application of a Monte Carlo model for an in vivo micro computed tomography system.

Micro computed tomography (µCT) scanners are used to create high-resolution images and to quantify properties of the scanned objects. While modern µCT scanners benefit from the cone beam geometry, they are compromised by scatter radiation. This work aims to develop a Monte Carlo (MC) model of a µCT scanner in order to characterize the scatter radiation in the detector plane. The EGS++ framework with the MC code EGSnrc was used to simulate the particle transport through the main components of the XtremeCT (SCANCO Medical AG, Switzerland). The developed MC model was based on specific information of the manufacturer and was validated against measurements. The primary and the scatter radiation were analyzed and by implementing a dedicated tracing method, the scatter radiation was subdivided into different scatter components. The comparisons of measured and simulated transmission values for different absorber and filter combinations result in a mean difference of 0.2% ±â€¯1.4%, with a maximal local difference of 3.4%. The reconstructed image of the phantom based on measurements agrees well with the image reconstructed using the MC model. The local contribution of scattered radiation is up to 10% of the total radiation in the detector plane and most of the scattered particles result from interactions in the scanned object. The MC simulations show that scatter radiation contains information about the structure of the object. In conclusion, a MC model for a µCT scanner was successfully validated and applied to analyze the characteristics of the scatter radiation for a µCT scanner.

Evaluation of high-resolution peripheral quantitative computed tomography, finite element analysis and biomechanical testing in a pre-clinical model of osteoporosis: a study with odanacatib treatment in the ovariectomized adult rhesus monkey.

This study aimed to validate finite element analysis (FEA) estimation of strength, identify high-resolution peripheral quantitative computed tomography (HR-pQCT) measures correlating with strength, and evaluate the precision of HR-pQCT measurements to longitudinally monitor effects of osteoporosis treatment in ovariectomized (OVX) non-human primates (NHPs). HR-pQCT images were acquired in three groups of NHPs: Intact (n=10), OVX-odanacatib treated (OVX-ODN 30 mg/kg, n=10) and OVX-vehicle treated (OVX-Veh, n=10) at the ultradistal (UD) and distal 1/3 radii and tibia at 12, 16 and 20 months. FEA estimates of bone strength using the Pistoia criterion were validated by ex-vivo mechanical compression (r(2)=0.95) of the UD radius. Single linear regressions of FEA-determined ultimate stress showed high correlation with HR-pQCT derived parameters: integral vBMD (r(2)=0.86), bone volume fraction (r(2)=0.84) and cortical thickness (r(2)=0.79). Precision of HR-pQCT measurements, obtained from an excised radius and tibia, showed low variation (CV=0.005%-5.6%) and helped identify possible sources of error. Comparison of OVX-Veh and Intact groups showed decreases in bone parameters demonstrating trends consistent with bone loss. Comparison of OVX-ODN and OVX-Veh groups showed a treatment effect with increases in bone parameters: integral vBMD (477±27 vs. 364±22 mgHA/cm(3)) and cortical thickness (Ct.Th) (0.90±0.07 vs. 0.64±0.04 mm) at the UD radius, Ct.Th (2.15±0.28 vs. 1.56±0.08 mm) at the distal 1/3 radius. Axial compression peak stress calculated and obtained experimentally showed the OVX-ODN group was 33% stronger than the OVX-Veh group. We conclude that HR-pQCT and FEA serve as robust techniques to longitudinally monitor bone parameters and strength in NHP's.

Reproducibility of direct quantitative measures of cortical bone microarchitecture of the distal radius and tibia by HR-pQCT.

Quantitative cortical microarchitectural end points are important for understanding structure-function relations in the context of fracture risk and therapeutic efficacy. This technique study details new image-processing methods to automatically segment and directly quantify cortical density, geometry, and microarchitecture from HR-pQCT images of the distal radius and tibia. An automated segmentation technique was developed to identify the periosteal and endosteal margins of the distal radius and tibia and detect intracortical pore space morphologically consistent with Haversian canals. The reproducibility of direct quantitative cortical bone indices based on this method was assessed in a pooled data set of 56 subjects with two repeat acquisitions for each site. The in vivo precision error was characterized using root mean square coefficient of variation (RMSCV%) from which the least significant change (LSC) was calculated. Bland-Altman plots were used to characterize bias in the precision estimates. The reproducibility of cortical density and cross-sectional area measures was high (RMSCV <1% and <1.5%, respectively) with good agreement between young and elder medians. The LSC for cortical porosity (Ct.Po) was somewhat smaller in the radius (0.58%) compared with the distal tibia (0.84%) and significantly different between young and elder medians in the distal tibia (LSC: 0.75% vs. 0.92%, p<0.001). The LSC for pore diameter and distribution (Po.Dm and Po.Dm.SD) ranged between 15 and 23 microm. Bland-Altman analysis revealed moderate bias for integral measures of area and volume but not for density or microarchitecture. This study indicates that HR-pQCT measures of cortical bone density and architecture can be measured in vivo with high reproducibility and limited bias across a biologically relevant range of values. The results of this study provide informative data for the design of future clinical studies of bone quality.

Hard-tissue debris accumulation analysis by high-resolution computed tomography scans.

INTRODUCTION: Hard-tissue debris accumulation is a potential side effect of root canal instrumentation that has not been systematically investigated. In the current communication, a method to assess this debris using high-resolution microcomputed tomography (microCT) is presented. METHODS: Based on prescans, mandibular molars with joining mesial root canals and isthmuses between these were selected (n = 6). The mean volume filled with apparent hard-tissue debris after instrumentation without irrigation was calculated over 2 mm of the mesial canal system by multiplying the voxel volume with the number of voxels representing acquired radiopaque material. Backscattered electron imaging was used to compare the calcium-phosphorus content of this material with that of the root dentin in the same specimen. RESULTS: Backscatter scans showed that the accumulated debris viewed in the microCT scans was consistent with root dentin. In the selected canal segments, 29.2% +/- 14.5% of the original canal volume was filled with accumulated debris, which represented a significant change from the preoperative scan (p < 0.01, one-sample t test against zero). Three-dimensional reconstructions of the microCT images visualized the accumulated hard-tissue debris in the whole canal system. CONCLUSIONS: The current method appears suitable to quantitatively compare different instrumenting/irrigating regimens on dentin debris accumulation.

Specimen size and porosity can introduce error into microCT-based tissue mineral density measurements.

The accurate measurement of tissue mineral density, rho(m), in specimens of unequal size or quantities of bone mineral using polychromatic microCT systems is important, since studies often compare samples with a range of sizes and bone densities. We assessed the influence of object size on microCT measurements of rho(m) using (1) hydroxyapatite rods (HA), (2) precision-manufactured aluminum foams (AL) simulating trabecular bone structure, and (3) bovine cortical bone cubes (BCt). Two beam-hardening correction (BHC) algorithms, determined using a 200 and 1200 mg/cm(3) HA wedge phantom, were used to calculate rho(m) of the HA and BCt. The 200 mg/cm(3) and an aluminum BHC algorithm were used to calculate the linear attenuation coefficients of the AL foams. Equivalent rho(m) measurements of 500, 1000, and 1500 mg HA/cm(3) rods decreased (r(2)>0.96, p<0.05 for all) as HA rod diameter increased in the 200 mg/cm(3) BHC data. Errors averaged 8.2% across these samples and reached as high as 29.5%. Regression analyses suggested no size effects in the 1200 mg/cm(3) BHC data but differences between successive sizes still reached as high as 13%. The linear attenuation coefficients of the AL foams increased up to approximately 6% with increasing volume fractions (r(2)>0.81, p<0.05 for all) but the strength of the size-related error was also BHC dependent. Equivalent rho(m) values were inversely correlated with BCt cube size (r(2)>0.92, p<0.05). Use of the 1200 mg/cm(3) BHC ameliorated the size-related artifact compared to the 200 mg/cm(3) BHC but errors with this BHC were still significant and ranged between 5% and 12%. These results demonstrate that object size, structure, and BHC algorithm can influence microCT measurements of rho(m). Measurements of rho(m) of specimens of unequal size or quantities of bone mineral must be interpreted with caution unless appropriate steps are taken to minimize these potential artifacts.

Quantitative assessment of bone tissue mineralization with polychromatic micro-computed tomography.

Micro-computed tomography (microCT) has become an important tool for morphological characterization of cortical and trabecular bone. Quantitative assessment of bone tissue mineral density (TMD) from microCT images may be possible; however, the methods for calibration and accuracy have not been thoroughly evaluated. This study investigated hydroxyapatite (HA) phantom sampling limitations, short-term reproducibility of phantom measurements, and accuracy of TMD measurements by correlation to ash density. Additionally, the performance of a global and a local threshold for determining TMD was tested. The full length of a commercial density phantom was imaged by microCT, and mean calibration parameters were determined for a volume of interest (VOI) at 10 random positions along the longitudinal axis. Ten different VOI lengths were used (0.9-13 mm). The root mean square error (RMSE) was calculated for each scan length. Short-term reproducibility was assessed by five repeat phantom measurements for three source voltage settings. Accuracy was evaluated by imaging rat cortical bone (n = 16) and bovine trabecular bone (n = 15), followed by ash gravimetry. Phantom heterogeneity was associated with <0.5% RMSE. The coefficient of variation for five repeat measurements was generally <0.25% across all energies and phantom densities. Bone mineral content was strongly correlated to ash weight (R (2) = 1.00 for both specimen groups and both threshold methods). Ash density was well correlated for the trabecular bone specimens (R (2) > 0.80). In cortical bone specimens, the correlation was somewhat weaker when a global threshold was applied (R (2) = 0.67) compared to the local threshold method (R (2) = 0.78).

High-resolution pQCT analysis at the distal radius and tibia discriminates patients with recent wrist and femoral neck fractures.

We depict a fragility bone state in two primitive osteoporosis populations using 3D high-resolution peripheral in vivo QCT (HR-pQCT). Postmenopausal women (C, controls, n = 54; WF, wrist, n = 50; HF, hip, n = 62 recent fractured patients) were analyzed for lumbar and hip DXA areal BMD (aBMD), cancellous and cortical volumetric BMD (vBMD), and microstructural and geometric parameters on tibia and radius by HR-pQCT. Principal component analysis (PCA) allowed extracting factors that best represent bone variables. Comparison between groups was made by analysis of covariance (ANCOVA). Two factors (>80% of the entire variability) are extracted by PCA: at the radius, the first is a combination of trabecular parameters and the second of cortical parameters. At the tibia, we found the reverse. Femoral neck aBMD is decreased in WF (8.6%) and in HF (18%) groups (no lumbar difference). WF showed a approximately 20% reduction in radius trabecular vBMD and number. Radius cortical vBMD and thickness decrease by 6% and 14%, respectively. At the tibia, only the cortical compartment is affected, with approximately 20% reduction in bone area, thickness, and section modulus and 6% reduction in vBMD. HF showed same radius trabecular alterations than WF, but radius cortical parameters are more severely affected than WF with reduced bone area (25%), thickness (28.5%), and vBMD (11%). At the tibia, trabecular vBMD and number decrease by 26% and 17.5%, respectively. Tibia cortical bone area, thickness, and section modulus showed a >30% decrease, whereas vBMD reduction reached 13%. Geometry parameters at the tibia displayed the greatest differences between healthy and fractured patients and between wrist and hip fractures.

Does weight gain induce cortical and trabecular bone regain in anorexia nervosa? A two-year prospective study.

This prospective study examines bone density and structure over a two-year time period in women with anorexia nervosa (AN) under weight gain treatment. Twenty-four women with AN were examined at baseline and at two annual follow-up examinations. In 9 AN patients BMI increased whereas in 15 it remained unchanged or decreased. Dual energy X-ray absorptiometry (DXA) was performed on the lumbar spine, the femoral neck and the whole hip and three-dimensional peripheral quantitative computer tomography (3D-pQCT) was performed on the ultradistal radius. ANOVAs for repeated measures were used to examine change over time in BMI and bone parameters. At baseline, patients with increased BMI had significantly higher bone density of femoral neck and total hip, and higher levels in all 3D-pQCT parameters of the ultradistal radius, compared to the group with unchanged or decreased BMI. The two groups did not differ at baseline in bone density of the spine. ANOVAs showed that bone density of the total hip increased significantly and that overall bone density (D100), the density of the trabecular area (D.Trab.) and the cortical thickness (C.Th.) in the ultradistal radius decreased significantly. Group x time interactions showed that changes over time were different in the two groups with regard to spine density and in the parameters D100, D.Trab. and C.Th. of the ultradistal radius. In the group with increased BMI the spine density dropped at the first follow-up whereas at the second follow-up it rose again to baseline. Patients with unchanged or decreased BMI showed a small but steady increase in spine density. The group changes of D100, D.Trab. and C.Th. of the ultradistal radius all followed the same pattern. Bone mineral density at all locations measured with both technologies (DXA and 3D-pQCT) did not vary according to BMI changes. The course of bone density and structure at different locations was different, and, despite weight increase, bone regain appeared to need different time periods.

The use of micro-CT to evaluate cortical bone geometry and strength in nude rats: correlation with mechanical testing, pQCT and DXA.

In both clinical and experimental settings, access to quantitative methods enabling the objective evaluation of cortical bone mass, structure, geometry and strength are essential for the assessment of efficacy and safety of different treatments aimed to improve bone strength. The ability of non-invasive methodologies (DXA, pQCT and micro-CT) to assess and quantify cortical bone mass and geometry was tested in a nude rat model in which bone loss was induced by surgical castration. Treatment with a bone antiresorptive (alendronate) or a bone forming (PTH) drug was used to: (A) validate the nude rat model in terms of bone metabolism, (B) test the ability of each technology to detect change in cortical bone geometry and (C) correlate cortical bone geometry with bone strength data obtained by 3-point bending method. Our observations regarding effect of castration and treatment with PTH and alendronate on cortical bone parameters in nude rats is in general agreement with previously published data obtained in immunocompetent male rats under similar experimental conditions. Data presented here support the hypothesis that nude rats have similar bone physiology and response to known bone therapies to that observed in normal rats and therefore could be effectively used to predict skeletal response in humans. All three technologies deployed in this study (DXA, pQCT and micro-CT) proved useful in describing cancellous and/or cortical bone parameters and positive correlations were demonstrated between data obtained by different methods. The cross-sectional area of a bone structure is crucial for resisting loads in bending or torsion and is described as "areal moment of inertia" for bending, and as "polar moment of inertia" in torsion. Novel, three-dimensional micro-CT methodology used in this study to assess geometry of cortical bone provides data that accurately describes cortical bone geometry and parallels cortical bone strength results obtained by the 3-point bending method. Our micro-CT data meet the criteria of providing quick, reproducible and accurate answers regarding cortical bone geometry as a predictor of cortical bone strength.

Noninvasive monitoring of changes in structural cancellous bone parameters with a novel prototype micro-CT.

Characterization of trabecular bone structures requires necropsy of animals followed by a labor-intense histomorphometric or ex vivo micro-CT analysis. We tested the novel vivaCT40 from Scanco Medical AG (Bassersdorf, Switzerland), which allows monitoring such changes repeatedly in anesthetized rats and mice. Postmenopausal osteoporosis: in 8-month-old ovariectomized (OVX) rats, the vivaCT40 was capable of picking up the decrease in trabecular bone volume and trabecular thinning as well as the decrease in the number of trabecular elements as a function of time. The bone anabolic effects of parathyroid hormone [hPTH(1-34)], which resulted in an increase in trabecular thickness but not their number, as well as the bone protective effect of the two antiresorptive agents zoledronic acid (ZA) and 17-alpha ethinylestradiol (aEE), were detected correctly with the vivaCT40. Adjuvans arthritis: the vivaCT40 allowed measuring trabecular bone loss caused by periarticular inflammation in a rat model of adjuvans arthritis and demonstrated the bone protective effect of dexamethasone (DM). In addition, it was possible to image the subtle erosive lesions in subchondral bone caused by the inflammatory processes. Tumor osteolysis: the vivaCT40 allowed monitoring of the progressive osteolytic response following the local administration of 4T1luc2000 tumor cells into the tibia metaphysis of nude mice. The potent protective effect of ZA on tumor osteolysis was demonstrated. In summary, the new vivaCT40 can monitor the effects of known agents and diseases such as osteoporosis, inflammatory arthritis, and tumor invasion on 3-D trabecular microarchitecture accurately, repeatedly, reliably, and quickly in anesthetized rats and mice. The scanner represents a breakthrough for noninvasive imaging and structural measurements in small rodents.

Comparison of measurements of phase velocity in human calcaneus to Biot theory.

Biot's theory for elastic propagation in porous media has previously been shown to be useful for modeling the dependence of phase velocity on porosity in bovine cancellous bone in vitro. In the present study, Biot's theory is applied to measurements of porosity-dependent phase velocity in 53 human calcanea in vitro. Porosity was measured using microcomputed tomography for some samples (n = 23) and estimated based on bone mineral densitometry for the remaining samples (n = 30). The phase velocity at 500 kHz was measured in a water tank using a through-transmission technique. Biot's theory performed well for the prediction of the dependence of sound speed on porosity. The trend was quasilinear, but both the theory and experiment show similar slight curvature. The root mean square error (RMSE) of predicted versus measured sound speed was 15.8 m/s.

Microcomputed tomographic analysis of the peri-implant bone.

A recently developed technology allows evaluation of bone biopsies with 3-D microcomputed tomography (microCT). The present study evaluated the feasibility of application of microCT to the analysis of peri-implant bone tissues. A human bone biopsy containing a titanium screw was analyzed using a microCT scan. The parameters computed by the microCT were bone volume, bone surface, trabecular thickness, trabecular separation, and bone connectivity. Also, the bone-to-implant apposition was measured, and all results were compared with those obtained with standard histomorphometry of the same biopsy. The results of the present study suggest that microCT enables 3-D nondestructive evaluation of bone biopsies containing endosseous titanium implants, also allowing analysis of the bone-implant interface. Measurements of bone-to-implant apposition obtained by microCT were similar to those obtained with standard undecalcified histology.

The dependence of ultrasonic backscatter on trabecular thickness in human calcaneus: theoretical and experimental results.

Trabecular thickness within cancellous bone is an important determinant of osteoporotic fracture risk. Noninvasive assessment of trabecular thickness potentially could yield useful diagnostic information. Faran's theory of elastic scattering from a cylindrical object immersed in a fluid has been used to predict the dependence of ultrasonic backscatter on trabecular thickness. The theory predicts that, in the range of morphological and material properties expected for trabecular bone, the backscatter coefficient at 500 kHz should be approximately proportional to trabecular thickness to the power of 2.9. Experimental measurements of backscatter coefficient were performed on 43 human calcaneus samples in vitro. Mean trabecular thicknesses on the 43 samples were assessed using micro computed tomography (CT). A power law fit to the data showed that the backscatter coefficient empirically varied as trabecular thickness to the 2.8 power. The 95% confidence interval for this exponent was 1.7 to 3.9. The square of the correlation coefficient for the linear regression to the log transformed data was 0.40. This suggests that 40% of variations in backscatter may be attributed to variations in trabecular thickness. These results reinforce previous studies that offered validation for the Faran cylinder model for prediction of scattering properties of cancellous bone, and provide added evidence for the potential diagnostic utility of the backscatter measurement.

Tail suspension induces bone loss in skeletally mature mice in the C57BL/6J strain but not in the C3H/HeJ strain.

We assessed the effects of tail-suspension in two skeletal genetic backgrounds, the high C3H/HeJ (C3H) and low C57BL/6J (B6) bone masses inbred mice (male, 4-months old). Cancellous bone mass and structural parameters were evaluated in distal femoral metaphysis by three dimensional microcomputed tomography. Bone cellular activities were evaluated by histomorphometry and measurements of alkaline phosphatase activity (ALP) and osteocalcin in blood and deoxypyridinoline (D-pyr) in urine. In C3H mice, 2- and 3-week unloading experiments were performed. After an early and transient decrease in body weight, a 2-week suspension period resulted in stimulation of both bone formation rate by 45% and active osteoclastic surfaces by 19%. D-pyr did not change, but ALP and osteocalcin levels increased by 18% and 72%, respectively, in 2-week suspended mice, and osteocalcin remained elevated by 30% in the 3-week suspended mice. Such cellular modifications allowed the C3H mice to maintain their initial bone mass and trabecular structural parameters even after a 3-week suspension period. In B6 mice, 1- and 2-week unloading experiments were performed. Tail suspension resulted in decreased body weight during the first days followed by an incomplete recovery during the second week of unloading. The resorption activity was unaffected by any suspension time period, whereas a decrease of 42.5% in bone formation rate and of 21.5% in ALP were seen by the end of the first week of suspension, both values being restored after a 2-week suspension period. At this latter time, trabeculae were thinner, leading to a 24.5% cancellous bone loss. Trabecular number and connectivity, rod-plate index, and degree of anisotropy were not modified. We concluded that C3H mice constituted a unique model in which genetic background overwhelmed the usual effects of reduced biomechanical usage in bone, whereas B6 mice, compared with the standardized rat model, offered an alternative model of bone loss in a mature skeleton.

MicroCT evaluation of normal and osteoarthritic bone structure in human knee specimens.

Although trabecular bone structure has been evaluated, variation with knee compartment and depth from joint surface is not completely understood. Cadaver knees were evaluated with microcomputed tomography analysis for these variations. Objective differences were compared between: medial vs. lateral compartments; femoral vs. tibial bone; and normal vs. arthritic knees. Depth dependent changes in the parameters were observed for the first 6 mm of the cores in normal knees: BV/TV, Tb.N and Conn.D gradually decrease, while Tb.Sp and SMI increase. In the first 6 mm of the normal tibia BV/TV, Tb.N, and Tb.Th are greater than in the femur on both the medial and lateral compartments while Tb.Sp, SMI, and Conn.D are lower. The medial compartment values for BV/TV, Tb.N, Tb.Th and Conn.D are generally greater than for the lateral in both the femur and tibia while Tb.Sp and SMI are lower. In comparison of normal vs. arthritic knees significant differences are observed in the first 6 mm of the medial tibia. With arthritis BV/TV and Tb.Th are lower, while SMI and Tb.Sp are higher. Tb.N and Conn.D show no statistically significant difference. The bone structure variations are, thus, most prominent in the first 6 mm of depth and medial compartment bone is generally more structurally sound than lateral. Severely arthritic bone changes are most prominent in the medial compartment of the tibia and bone structure is less sound in severe arthritis.

Three-dimensional-line skeleton graph analysis of high-resolution magnetic resonance images: a validation study from 34-microm-resolution microcomputed tomography.

The resolution achievable in vivo by magnetic resonance imaging (MRI) techniques is not sufficient to depict precisely individual trabeculae and, thus, does not permit the quantification of the "true" trabecular bone morphology and topology. Nevertheless, the characterization of the "apparent" trabecular bone network derived from high-resolution MR images (MRIs) and their potential to provide information in addition to bone mineral density (BMD) alone has been established in studies of osteoporosis. The aim of this work was to show the ability of the three-dimensional-line skeleton graph analysis (3D-LSGA) to characterize high-resolution MRIs of trabecular bone structure. Fifteen trabecular bone samples of the distal radius were imaged using the high-resolution MRI (156 x 156 x 300 microm3) and microcomputed tomography (microCT; 34 x 34 x 34 microm3). After thresholding, the 3D skeleton graph of each binary image was obtained. To remove the assimilated-noise branches of the skeleton graph and smooth this skeleton graph before it was analyzed, we defined a smoothing length criterion (l(c)), such that all "termini" branches having a length lower than l(c) were removed. Local topological and morphological LSGA measurements were performed from MRIs and microCT images of the same samples. The correlations between these two sets of measurements were dependent on the smoothing criterion l(c), reaching R2 = 0.85 for topological measurements and R2 = 0.57-0.64 for morphological measurements. 3D-LSGA technique could be applied to in vivo high-resolution MRIs of trabecular bone structure, giving an indirect characterization of the microtrabecular bone network.

Local differences in the trabecular bone structure of the proximal femur depicted with high-spatial-resolution MR imaging and multisection CT.

RATIONALE AND OBJECTIVES: The authors performed this study to investigate structural variations in the trabecular bone of the proximal femur at high-resolution magnetic resonance (MR) imaging and high-resolution multisection computed tomography (CT). MATERIALS AND METHODS: Bone mineral density (BMD) was measured in 36 proximal human femur specimens by using dual x-ray absorptiometry. High-resolution MR imaging was performed at 1.5 T with an in-plane spatial resolution of 0.195 x 0.195 mm and a section thickness of 0.3 and 0.9 mm. Multisection CT was performed with an ultra-high-resolution protocol; images were obtained with an in-plane spatial resolution of 0.25 mm and a section thickness of 1 mm. In a subset of these specimens, micro CT was performed with an isotropic spatial resolution of 30 microm. Identical regions of interest (ROIs) were used to analyze images obtained with MR imaging, multisection CT, and micro CT. Trabecular bone structural parameters were obtained, and the parameters from the individual imaging modalities and BMD were correlated. RESULTS: Significant differences concerning the trabecular microarchitecture between the individual ROIs were demonstrated with multisection CT and MR imaging. A number of the correlations between structural parameters derived with multisection CT, MR imaging, micro CT, and BMD measurements were significant. For MR imaging, threshold technique and section thickness had an effect on structural parameters. CONCLUSION: Structural parameters obtained in the proximal femur with multisection CT and high-resolution MR imaging show regional differences. These techniques may be useful for depicting the trabecular architecture in the diagnosis of osteoporosis.