Quantitative peripheral computed tomodensitometric study of cortical and trabecular bone mass in relation with menopause

Changes in total, cortical and trabecular bone mass were studied using quantitative peripheral computed tomodensitometry on the forearm of 58 normal eugonadal premenopausal women and 116 normal postmenopausal women to evaluate the evolution of bone components with age. In premenopausal women, no changes were seen in any bone component. In postmenopausal women, only trabecular bone mass diminished in the first 5 years after menopause (P < 0.05). It continued to decrease in the next 5 years (P < 0.05), but not later. Cortical bone mass experienced a significant loss 6–10 years after menopause (P < 0.001), and more than 15 years after menopause (P < 0.0005). These results are similar to those obtained with other techniques, and document the differing behavior of the cortical and trabecular bone components with years of menopause.     

Prediction of mechanical properties of cortical bone by quantitative computed tomography

The relevance of Finite-Element models for hip fracture prediction should be increased by the recent subject-specific methods based on computed tomography (CT-scan), regarding the geometry as well as the material properties. The present study focused on the prediction of subject-specific mechanical parameters of cortical bone (Young's modulus and ultimate strength) from the bone density measured by CT. A total of 46 compression and 46 tension samples from 13 donors (mean age+/-S.D.: 81.8+/-12.7 years) were harvested in the femoral mid-diaphysis and tested until failure. The Young's modulus and ultimate strength were linearly correlated with the bone density measured by CT, for tension as well as compression (0.43相似文献   

Accuracy of high-resolution peripheral quantitative computed tomography for measurement of bone quality

The introduction of three-dimensional high-resolution peripheral in vivo quantitative computed tomography (HR-pQCT) (XtremeCT, Scanco Medical, Switzerland; voxel size 82 μm) provides a new approach to monitor micro-architectural bone changes longitudinally. The accuracy of HR-pQCT for three important determinants of bone quality, including bone mineral density (BMD), architectural measurements and bone mechanics, was determined through a comparison with micro-computed tomography (μCT) and dual energy X-ray absorptiometry (DXA). Forty measurements from 10 cadaver radii with low bone mass were scanned using the three modalities, and image registration was used for 3D data to ensure identical regions were analyzed.

The areal BMD of DXA correlated well with volumetric BMD by HR-pQCT despite differences in dimensionality (R² = 0.69), and the correlation improved when non-dimensional bone mineral content was assessed (R² = 0.80). Morphological parameters measured by HR-pQCT in a standard patient analysis, including bone volume ratio, trabecular number, derived trabecular thickness, derived trabecular separation, and cortical thickness correlated well with μCT measures (R² = 0.59–0.96). Additionally, some non-metric parameters such as connectivity density (R² = 0.90) performed well. The mechanical stiffness assessed by finite element analysis of HR-pQCT images was generally higher than for μCT data due to resolution differences, and correlated well at the continuum level (R² = 0.73).

The validation here of HR-pQCT against gold-standards μCT and DXA provides insight into the accuracy of the system, and suggests that in addition to the standard patient protocol, additional indices of bone quality including connectivity density and mechanical stiffness may be appropriate to include as part of a standard patient analysis for clinical monitoring of bone quality.     

Improved reproducibility of high-resolution peripheral quantitative computed tomography for measurement of bone quality

A human high-resolution peripheral quantitative computed tomography scanner (HR-pQCT) (XtremeCT, Scanco Medical, Switzerland) capable of measuring three important indicators of bone quality (micro-architectural morphology, mineralization and mechanical stiffness) has been developed. The goal of this study was to evaluate the reproducibility of male and female HR-pQCT in vivo measurements, and elucidate the causes of error in these measurements through a comparison with in vitro measurements. The best possible short-term reproducibility was found using a set of 10 in vitro measurements without repositioning, and a set of 10 with repositioning. Subsequently, in vivo measurements were performed on 15 male and 15 female subjects at baseline and follow-ups of 1 week and 4 months to determine the short- and long-term reproducibility of the system. In addition to the 2D area matching method used in the standard evaluation protocol, a custom developed 3D registration method was used to find the common region between repeated scans. The best possible reproducibility without movement artifacts and repositioning error was less than 0.5%, while the reproducibility with repositioning error was less than 1.5%. The in vivo reproducibility of density (<1%), morphological (<4.5%) and stiffness (<3.5) measurements was consistently poorer than the reproducibility of cadaver measurements, presumably due to small movement artifacts and repositioning errors. Using 3D image registration, repositioning error was reduced on average by 23% and 8% for measurements of the radius and tibia sites, respectively. This study has provided bounds for the reproducibility of HR-pQCT to monitor bone quality longitudinally, and a basis for clinical study design to determine detectable changes.     

Peripheral quantitative computed tomography in evaluation of bioactive glass incorporation with bone

This laboratory study examined the feasibility of non-invasive, in vivo peripheral quantitative computed tomography (pQCT) method in evaluation of bioactive glass incorporation with bone. An intramedullary defect model of the rat tibia was applied. The defect was filled with bioactive glass microspheres (diameter of 250-315 microm) or was left to heal without filling (empty controls). The results of the pQCT analysis were compared with those of histomorphometry. In the control defects, there was a good correlation (r2 = 0.776, p < 0.001) between the pQCT density of the intramedullary space and the amount of new bone measured by histomorphometry. In the defects filled with bioactive glass, the use of thresholding techniques of the applied pQCT system (Stratec XCT Research M) failed in separation of new bone formation and bioactive glass particles. However, detailed analysis of the pQCT attenuation profiles showed time-related changes which well matched with the histomorphometric results of new bone formation both in control and bioactive glass filled defects. The biphasic pQCT attenuation profiles of bioactive glass filled defects could be separated into two distinct peaks. In statistical analysis of various variables, the center (i.e. the value of attenuation) of the major attenuation peak was found to be the most significant indicator of the incorporation process. The center of the peak initially decreased (during the first 4 weeks of healing) and thereafter increased. These two phases probably reflect the primary resorption and reactivity of the bioactive glass microspheres in vivo followed by secondary new bone formation on their surfaces. Based on these results, pQCT-method seems to be suitable for in vivo follow-up of the bioactive glass incorporation processes. Although the imaging technique is not able to discriminate the individual microspheres from invading new bone unambiguously, the attenuation profiling seems to give adequate information about the state of the incorporation process. This information may help to establish non-invasive imaging techniques of synthetic bone substitutes for preclinical and clinical testing of their efficacy.     

Treatment of subclinical hypothyroidism does not affect bone mass as determined by dual-energy X-ray absorptiometry,peripheral quantitative computed tomography and quantitative bone ultrasound in Spanish women

Introduction

The results of studies examining the influence of subclinical hypothyroidism (SCH) and levothyroxine (L-T₄) replacement therapy on bone have generated considerable interest but also controversy. The present research aims to evaluate the effects of L-T₄ treatment on different skeletal sites in women.

Material and methods

A group of 45 premenopausal (mean age: 43.62 ±6.65 years) and 180 postmenopausal (mean age: 59.51 ±7.90 years) women with SCH who were undergoing L-T₄ replacement therapy for at least 6 months were compared to 58 pre- and 180 postmenopausal women with SCH (untreated) matched for age. The mean doses of L-T₄ were 90.88 ±42.59 µg/day in the premenopausal women and 86.35 ±34.11 µg/day in the postmenopausal women. Bone measurements were obtained using quantitative bone ultrasound (QUS) for the phalanx, dual-energy X-ray absorptiometry (DXA) for the lumbar spine and hip, and peripheral quantitative computed tomography (pQCT) for the non-dominant distal forearm.

Results

No differences were observed between patients and untreated controls in these bone measurements except in the bone mineral density (BMD) of the spine (p = 0.0214) in postmenopausal women, which was greater in treated women than in untreated controls.

Conclusions

Our results indicate that adequate metabolic control through replacement treatment with L-T₄ in pre- and postmenopausal women does not affect bone mass.     

Carpal bone maturation during childhood and adolescence: Assessment by quantitative computed tomography

The aim of our study was to measure the volume of each carpal bone during childhood and adolescence by image processing from computed tomography (CT) scans, and to analyze the relationship between the eight carpal bones. Thirteen CT scans were performed in nine normal prepubertal, peripubertal and post-pubertal children, six boys and three girls, aged 5-14 years. Each scan was processed in order to extract the carpal bones. The volume was computed for each bone. There was a significant correlation between carpal bone volume and age (0.55 < r < 0.79), and a very strong correlation between the volume of a given carpal bone and the volume of all the others, whatever the age (0.87 < r < 0.99, p < 0.01). Image processing is a potentially useful method for assessing bone maturation. The constant ratio between carpal bone volumes indicates that these bones interact with each other in wrist bone maturation     

Carpal bone maturation during childhood and adolescence: Assessment by quantitative computed tomography

The aim of our study was to measure the volume of each carpal bone during childhood and adolescence by image processing from computed tomography (CT) scans, and to analyze the relationship between the eight carpal bones. Thirteen CT scans were performed in nine normal prepubertal, peripubertal and post-pubertal children, six boys and three girls, aged 5-14 years. Each scan was processed in order to extract the carpal bones. The volume was computed for each bone. There was a significant correlation between carpal bone volume and age (0.55 < r < 0.79), and a very strong correlation between the volume of a given carpal bone and the volume of all the others, whatever the age (0.87 < r < 0.99, p < 0.01). Image processing is a potentially useful method for assessing bone maturation. The constant ratio between carpal bone volumes indicates that these bones interact with each other in wrist bone maturation     

Similar damage initiation but different failure behavior in trabecular and cortical bone tissue

The mechanical properties of bone tissue are reflected in its micro- and nanostructure as well as in its composition. Numerous studies have compared the elastic mechanical properties of cortical and trabecular bone tissue and concluded that cortical bone tissue is stiffer than trabecular bone tissue. This study compared the progression of microdamage leading to fracture and the related local strains during this process in trabecular and cortical bone tissue. Unmachined single bovine trabeculae and similarly-sized cortical bovine bone samples were mechanically tested in three-point bending and concomitantly imaged to assess local strains using a digital image correlation technique. The bone whitening effect was used to detect microdamage formation and propagation. This study found that cortical bone tissue exhibits significantly lower maximum strains (trabecular 36.6%±14% vs. cortical 22.9%±7.4%) and less accumulated damage (trabecular 16100±8800 pix/mm2 vs. cortical 8000±3400 pix/mm2) at failure. However, no difference was detected for the maximum local strain at whitening onset (trabecular 5.8%±2.6% vs. cortical 7.2%±3.1%). The differences in elastic modulus and mineral distribution in the two tissues were investigated, using nanoindentation and micro-Raman imaging, to explain the different mechanical properties found. While cortical bone was found to be overall stiffer and more highly mineralized, no apparent differences were noted in the distribution of modulus values or mineral density along the specimen diameter. Therefore, differences in the mechanical behavior of trabecular and cortical bone tissue are likely to be in large part due to microstructural (i.e. orientation and distribution of cement lines) and collagen related compositional differences.     

Structural analysis of the mandible by quantitative computed tomography

Summary The study presents quantitative computed tomography (QCT) as a noninvasiv method for analyzing the inner bone structure. Randomly selected mandibles from the osteological collection of the Drago Perovi Institute of Anatomy, School of Medicine, Zagreb were CT-scanned in five bone areas. Analyzing the densitometry curve in two horizontal levels the relation between the compact and spongy bone and the total amount of bone substance in each area were determined. The smallest bone quantity was found in the area of the neck and angle of the mandible, the areas of most frequent bone fractures. The alveolar part of the bone, apart from the area of the angle, was considerably less thick than the base of the mandible. The compact bone was predominant in all CT-scans.

---

Analyse structurale de la mandibule par tomographie assistée par ordinateur

Résumé Cette étude présente la tomographie quantitative assistée par ordinateur comme une méthode non exclusive d'analyse de la structure interne de l'os. Des mandibules choisies au hasard dans la collection ostéologique de l'institut Drago Perovi d'Anatomie de l'Ecole de Médecine de Zagreb furent examinées en 5 positions par CT. A partir de l'examen de la courbe densitométrique en deux niveaux horizontaux, les relations entre les parties spongieuses et compactes de l'os d'une part, et la quantité totale de substance osseuse d'autre part, dans chaque zone, furent déterminées. La plus petite quantité de substance osseuse fut trouvée dans les zones du col et de l'angle de la mandibule, siège le plus fréquent des fractures de l'os. La partie alvéolaire de l'os, à l'exception de celle de l'angle, était considérablement moins épaisse que la base de la mandibule. L'os compact prédominait dans tous les examens par CT.

     

Overestimation of osteopenia using standard analysis software for peripheral quantitative computed tomography

Summary It is well established that measurement of bone mineral density (BMD) can estimate the risk of future fractures. To assess individual fracture risk BMD measurements are compared with a reference range provided by the manufacturer of the respective BMD technology. However, the power of trabecular bone measured by peripheral quantitative computed tomography (pQCT) to predict future fractures has not been shown up to now. We conducted measurements of trabecular bone density (TBD) at the distal radius (pQCT XCT 900, Stratec, Germany) in a sample of 506 healthy white women aged 40–60 years (mean 48) and compared the results with the manufacturer's normal range. We found a remarkable difference in TBD values between our healthy study population and the manufacturer's reference data in all age groups (e.g., age 50–54 years, 143.1 ± 43.2 mg/cm³ versus 181.1 ± 39.0 mg/cm³). Compared to the ± 2 SD limits of the manufacturer's reference range our study population showed mean TBD values that were about 1 SD below the mean of the reference range. About 50% of our healthy cohort were below the –1 SD limit of the reference range. Almost ten times as many normal subjects as expected (22.1%) were found below the –2 SD limit and therefore classified as individuals with increased fracture risk. This overestimation of fracture risk leads to discomfort of the patient, unnecessary therapeutic intervention, and significant costs to the public. This difference is probably due to the fact that the manufacturer's reference values were generated with the older device (SCT 900) using a ¹²⁵I source, and that these were later used in devices with an X-ray source. Correction of the manufacturer's software is now underway; all devices with X-ray source distributed in Germany by the company must receive a new software with a generally agreed reference data-set. Our study indicates that a reliable reference database must become a prerequisite for the approvement of BMD technology prior to the use in patients.Abbreviations pQCT peripheral quantitative computed tomography - TBD trabecular bone density - BMD bone mineral density This work was supported by grants from BKK Deutsche Bank and Rhone Poulenc Rorer     

The potential of multi-slice computed tomography based quantification of the structural anisotropy of vertebral trabecular bone

In the present paper we addressed the problem of whether the information about the structural anisotropy of trabecular bone can be retrieved from low-quality data, captured with clinical multi-raw spiral CT scanners. Two measures of quantifying structural anisotropy were tested – the current standard mean intercept length (MIL) and the gray-level structure tensor (GST). Thirty two vertebral bodies were μCT and CT scanned. The reference values of structural anisotropy were measured in μCT images and compared with the measures of structural anisotropy determined from low-quality CT data. MIL-based measures of structural anisotropy cannot be reliably determined from CT data. The assessment of the GST is significantly better than that of MIL, but the accuracy is not, in general, satisfactory. Based on the results of experiments with artificial data and the analysis of the real images, it can be concluded that a possible reason of the poor performance is anisotropic resolution of clinical CT scanners.     

Systematic errors in bone-mineral measurements by quantitative computed tomography

Bone-mineral measurements using quantitative computed tomography (QCT) are commonly based on comparisons with solutions in water of known concentrations of K2HPO4. In this paper are described theoretical and experimental studies that have led to the conclusion that large systematic errors can arise in these measurements, depending on the soft-tissue and fat concentrations in the vertebral spongiosa. In the case of single energy scanning, such large errors have been identified to be due to the varying water content (displacement effect) in the calibration samples and the varying fat content in the region of interest (ROI) within the patient. In the case of dual energy scanning, the error arises because when normalized to that of water, the mass attenuation coefficient of fat increases with photon energy while the reverse is true for K2HPO4. Our studies have also revealed that total trabecular bone density (which includes the mineral, soft tissue, and fat) can be much more accurately determined by the dual energy QCT method than bone mineral alone. This finding is especially interesting since there have been several reports in the literature suggesting that bone density rather than bone-mineral content is a better predictor of the risk of osteoporosis-related fractures.     

Biometry of the infrarenal inferior vena cava measured by computed tomography

Summary In a previous study based upon the cavography of 100 patients, we determined that the average diameter of the infrarenal inferior v. cava (IIVC) was 21.3 mm (range 10 – 31 mm) at its end [1]. We discuss the value of different methods to measure IIVC, and particularly computed tomography (CT) scans reviewed in our department. It showed that the largest diameter of IIVC was not in a frontal plane and the width observed in a cavography was in fact the projection of a transverse diameter on the film. The real diameter of the IIVC is larger than that showed by cavography. This present study shows the results of measurement of the IIVC obtained from 50 consecutive CT scans. The average transverse diameter is 24.26 mm (range 14 – 33.3). The average anteroposterior diameter is 13.4 mm (range 5 – 22) and the average angle between the transverse diameter and the frontal plane is 30°45 (range 12°–55°). We discuss the different methods of measurement of IIVC and we conclude that at present, CT scan is one of the most reliable methods to measure the real diameter of IIVC.

---

Biométrie de la veine cave inférieure sous rénale : mesure par tomodensitométrie. Applications cliniques

Résumé Nous avions déterminé lors d'une étude réalisée en 1989 à partir de 100 cavographies la valeur du diamètre moyen de la v. cave inférieure sous rénale (VCISR) qui était de 21,3 mm (extrêmes 10–31 mm) [1]. La valeur des différentes méthodes de mesure de la VCISR, et en particulier la tomodensitométrie, a été discutée. Cette dernière montre en fait que le diamètre transversal de la VCISR n'est pas dans un plan frontal mais forme avec lui un angle variable appelé . Le diamètre observé sur une cavographie étant en réalité la projection d'un diamètre transversal sur le film, le diamètre réel de la veine est donc plus large. L'étude actuelle a pour but la mesure des diamètres de la VCISR et de l'angle . Le diamètre moyen transversal est de 24,26 mm (extrêmes 14– 33 mm). Le diamètre moyen antéro-postérieur est de 13,4 (extrêmes 5–22 mm). L'angle mesure en moyenne 30°45 (extrêmes 12°–55°). Nous discutons la valeur des différentes méthodes pour mesurer le diamètre de la VCISR et pour conclure que les valeurs les plus proches de la réalité sont obtenues avec la tomodensitométrie.

     

Relationship between indices of adiposity obtained by peripheral quantitative computed tomography and dual-energy X-ray absorptiometry in pre-pubertal children

Background/Aim: The study investigated the relationship between indices of adiposity measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA) in pre-pubertal children.

Subjects and methods: DXA-derived per cent body fat (%BF) was measured in 284 boys and 288 girls, aged 7–10 years. Cross-sections of the forearm (n=427) and lower leg (n=560) were obtained by pQCT to measure total cross-sectional area of the limb (Total CSA), Muscle CSA, Fat CSA, %Fat CSA (Fat CSA/Total CSA×100) and muscle density.

Results: Peripheral QCT-derived %Fat CSA in the forearm and lower leg correlated strongly with DXA-derived %BF (r=0.83–0.89, p<0.01) in both boys and girls. However, forearm and lower leg %Fat CSA were higher than whole body %BF by 5% and 10%, respectively. A better prediction of whole-body %BF was achieved by including %Fat CSA, muscle density and height into a hierarchical regression model. Using sex-specific regression equations, 87.7% of the boys and 83.7% of the girls had a predicted %BF within 3% units of the %BF obtained by DXA.

Conclusion: In pre-pubertal children, pQCT measures of adiposity are strongly associated with whole-body per cent body fat. This reproducible method could be an alternative technique to estimate body composition in this population.     

Performance evaluation of density measurements of axial and peripheral bone with x-ray and gamma-ray computed tomography

We examined sources of error in bone measurements made with computed tomography (CT) using a whole-body scanner (GE 8800) and a peripheral-bone CT scanner (developed at the University of Alberta). We investigated the influence of various factors on trabecular bone density: homogeneity and noise in the image plane, linearity of calibration, body size, effects of cortical bone, and the image analysis procedure. With the GE 8800 scanner, the precision (SD) of measurements of a single vertebra is expected to be +/- 1.65% (noise: +/- 0.22%, calibration: +/- 1.3%, analysis: +/- 1%); the accuracy, excluding consideration of marrow fat, varied between -2.7 and +7.3% (compact-bone thickness: 2-5%, body size: -2.5 - +1.5%, calibration: -0.47 - +0.77%). With the peripheral-bone CT scanner, the total precision error (+/- 0.53%) was dominated by noise, with only a minor contribution from the analysis procedure (+/- 0.04%); accuracy varied between -0.6 and +3.4% (effect of cortical bone: up to 3.0%; changes in size of object: -0.59 - +0.4%). The magnitude of these errors was determined under 'ideal' conditions, mostly through phantom measurements; therefore, the errors represent optimistic lower limits in clinical application. Furthermore, measurements of density of cortical bone were not reliable for bone thicknesses of less than about 4 mm with the GE 8800 scanner and less than about 1.5 mm with the peripheral scanner.     

3D micro-computed tomography of trabecular and cortical bone architecture with application to a rat model of immobilisation osteoporosis

Bone mass and microarchitecture are the main determinants of bone strength. Three-dimensional micro-computed tomogrpahy has the potential to examine complete bones of small laboratory animals with very high resolution in a non-invasive way. In the presented work, the proximal part of the tibiae of hindlimb unloaded and control rats were measured with 3D MicroCT, and the secondary spongiosa of the scanned region was evaluated using direct evaluation techniques that do not require model assumptions. For determination of the complete bone status, the cortex of the tibiae was evaluated and characterised by its thickness. It is shown that with the proposed anatomically conforming volume of interest (VOI), up to an eight-fold volume increase can be evaluated compared to cubic or spherical VOIs. A pronounced trabecular bone loss of −50% is seen after 23 days of tail suspension. With the new evaluation techniques, it is shown that most of this bone loss is caused by the thinning of trabeculae, and to a lesser extent by a decrease in their number. What changes most radically is the structure type: the remaining bone is more rod-like than the control group's bone. Cortical bone decreases less than trabecular bone, with only −18% after 23 days.     

Mechanisms governing the inelastic deformation of cortical bone and application to trabecular bone

To understand the inelastic response of bone, a three-part investigation has been conducted. In the first, unload/reload tests have been used to characterize the hysteresis and provide insight into the mechanisms causing the strain. The second part devises a model for the stress/strain response, based on understanding developed from the measurements. The model rationalizes the inelastic deformation in tension, as well as the permanent strain and hysteresis. In the third part, a constitutive law representative of the deformation is selected and used to illustrate the coupled buckling and bending of ligaments that arise when trabecular bone is loaded in compression.     

Assessment of cortical and trabecular bone distribution in the beagle skeleton by neutron activation analysis

The distribution of bone calcium between morphologically identifiable cortical and trabecular bone obtained by dissection and quantitated by neutron activation analysis (NAA) is described. The skeleton of a female beagle dog was dissected into approximately 400 pieces and assayed for ⁴⁹Ca produced in the University of California, Irvine TRIGA reactor. For each of the skeletal sections, we give the initial weight of the alcohol-fixed tissue, which includes cortical bone, trabecular bone, marrow, and cartilage, and a final tissue weight after the marrow and trabecular bone have been dissected away; total section and cortical section calcium weights are reported. The level of detail is represented, for example, by the vertebrae, which were divided into three parts (body, spine, and transverse processes) and by the long bones, which were divided into 10–12 parts such that characterization of the epiphysis, metaphysis, and diaphysis was accomplished. The nedian percentage cortical calcium values for cervical, thoracic, and lumbar vertebrae were 82%, 56%, and 66%, respectively; however, variation within these groups and among individual vertebral sections was about a factor of 2. For long bones, the median percentage cortical calcium varied from 90–100% in the midshaft to below 50% in the proximal and distal sections. The final calculated cortical tissue-to-calcium mass ratio (TCR) varied from about 4.5 for midshafts of the long bones to about 9 for thoracic vertebral bodies and indicated that the mineral fraction of cortical bone is not constant throughout the skeleton. The ratio of cortical to trabecular calcium in the skeleton was 79.6:20.4.