Distribution of intracortical porosity in human midfemoral cortex by age and gender.

The purpose of this study was to describe the age-specific distribution of midfemoral intracortical porosity throughout the cortical width in males and females. Microradiography and an automated image analysis system were used to study midfemoral cortical bone specimens from 163 white people, including 77 males and 86 females, in a recent anthropological collection covering a broad age range. In each specimen, porosity (percentage of the cortical bone area occupied by pores), pore number, and pore size were measured throughout the entire cortex and in three cortical subregions of equal width labeled the periosteal, midcortical, and endosteal subregions. For each gender, relationships linking age to porosity, pore number, and mean pore size were assessed using regression analysis. In addition, age- and site-related changes in these three variables were tested for significance using two-way analysis of variance (ANOVA). Age explained 52% of the porosity variance in females and 13.5% in males. In each gender, there were significant age- and site-related differences in porosity, pore number, and pore size. In adults aged 60 years or younger, both pore size and pore number increased with increasing age, whereas in adults older than 60 years, pore size continued to increase but pore number decreased. In males, the age-related changes in pore size and pore number were proportionally similar in the three cortical subregions. In females, in contrast, the changes predominated in the endosteal subregion and resulted in significant cortical thinning.

In vitro assessment of the relationship between acoustic properties and bone mass density of the calcaneus by comparison of ultrasound parametric imaging and quantitative computed tomography.

This in vitro study aimed to add new experimental evidence to clarify the relation between acoustic properties of bone and bone mineral density (BMD) of the human calcaneus. Parametric images of normalized broadband ultrasonic attenuation (nBUA) and ultrasound bone velocity (UBV) were compared with quantitative computed tomography (QCT) images of the calcaneus. The experimental protocol was designed to control the different potential sources of error in acoustic measurements, including the shape and thickness of the samples, intervening soft tissues and cortical bone, boundary effects, and variation in location of the regions of interest (ROIs) analyzed by ultrasound and X-ray. The present study was based on bone specimens from calcaneus removed from 15 cadavers (six male and nine female donors ranging from 69 to 89 years of age). Immersion ultrasonic measurements were performed in the through-thickness direction at normal incidence using a pair of focused broad-band 0.5-MHz transducers. QCT of the specimens was performed using standard 10-mm-thick slices with the Cann-Genant calibration standard. Identical, site-matched ROIs were selected for quantitative analysis on the three images. The pattern of acoustic parameters was similar to that of BMD with QCT. The relationships between nBUA and BMD (r2 = 0.75), between UBV and BMD (r2 = 0.88) and between nBUA and UBV (r2 = 0.84) were highly significant (p < 10(-4). From this study, it appears that ultrasound parameters as measured with current transmission techniques reflect mainly bone quantity and only reflect microarchitecture to a small extent and that BUA and UBV reflect the same bone property.

Importance of measurement of spongious vertebral bone mineral density in the assessment of osteoporosis.

Quantitative computed tomography (QCT) measurements of bone mineral density, volume, and content were made of the spongious and compact portions of a vertebral body and of the total vertebral body in 19 osteoporotic patients (13 women and 6 men) and 20 normal (control) age- and sex-matched patients. Specifically, CT scans of 10mm thick transverse sections of L2 or L3 of each osteoporotic and control patient were subjected to QCT bone measurement with the use of K2HPO4 calibration for converting CT values into units (mg/ml) equivalent to bone mineral density. In every instance, a significant difference was found in the spongious vertebral bone mineral density (and content) between the osteoporotic and the paired normal groups. Even when the total vertebral bone mineral content was normal, the spongious vertebral bone mineral density was significantly less in the osteoporotic patients. Only in the osteoporotic men was a difference in compact bone density (and content) found; the osteoporotic men had a significantly lower compact bone mineral than did the normal male patients. This study shows that QCT can be applied to measurement of bone mineral density (and content) of both the anterior spongious and the more dense compact vertebral bone from a single section of a lumbar vertebra and that it is the anterior, spongious, vertebral bone rather than the compact vertebral bone that exhibits the more severe decrease in bone mineral density (and content) due to osteoporosis.

Dual X-ray absorptiometry--cross-calibration and normative reference ranges for the spine: results of a European Community Concerted Action.

Bone density measurements by dual X-ray absorptiometry (DXA) of the spine can now be made precisely, but there is no uniformity in reporting results and in presenting reference data. A European Union Concerted Action therefore devised a uniform procedure for cross-calibrating and standardizing instruments, using the European spine phantom (ESP) prototype. This phantom differs in a number of respects from the final version of the ESP. Eighteen centers in nine countries obtained 1619 records (1035 women) from Caucasian subjects, aged 20-80 years, drawn from normal populations. The DXA machines used were made by the Hologic, Lunar, and Norland companies. Highly statistically significant differences were evident between populations, both in apparent rates of bone loss with age and in the spread of values about the age-adjusted means. There were small residual differences in the results obtained with the three machine brands which could have been due to the relatively large between-center population differences we observed. The alternative or additional explanation that they were attributable, in part, to the design differences between the ESP prototype and the definitive ESP, which became available after this study was completed, was shown to be a valid possibility. Results from postmenopausal women reported in relation to the years that have elapsed since menopause showed reduced population variance when compared with conventional reporting in relation to age. After cross-calibration, the center with the highest age-adjusted normal density value averaged 23% more than the center with the lowest. It is therefore crucially important to select appropriate reference data in clinical and epidemiological studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of particle size on the tissue distribution of iodized emulsified fat following intravenous administration.

Three iodinated fat emulsions were tested by intravenous injection to rats: coarse with a mean size of particles of 7 micrometers, fine with a mean size of 1.3 micrometers, and ultrafine with a mean size of 0.7 micrometers. Iodine content analysis and scintigraphy of radioactive iodinated emulsions show important differences. Coarse emulsion is almost entirely fixed in the liver and the lungs; fine emulsion has a higher relative liver fixation; and ultrafine emulsion has a hepatosplenic fixation of short duration. Degradation of contrast medium is slow with coarse emulsion and very fast with ultrafine emulsion which is responsible for the rising iodine concentration in blood. Fine emulsion is a good compromise between excessive pulmonary fixation of coarse emulsion and high iodine peak in the blood after injections of ultrafine emulsion. The dose of 0.2 ml/kg of fine emulsion gives persistent enhancement of hepatic parenchyma without significant toxicity.

A synchrotron radiation microtomography system for the analysis of trabecular bone samples.

X-ray computed microtomography is particularly well suited for studying trabecular bone architecture, which requires three-dimensional (3-D) images with high spatial resolution. For this purpose, we describe a three-dimensional computed microtomography (microCT) system using synchrotron radiation, developed at ESRF. Since synchrotron radiation provides a monochromatic and high photon flux x-ray beam, it allows high resolution and a high signal-to-noise ratio imaging. The principle of the system is based on truly three-dimensional parallel tomographic acquisition. It uses a two-dimensional (2-D) CCD-based detector to record 2-D radiographs of the transmitted beam through the sample under different angles of view. The 3-D tomographic reconstruction, performed by an exact 3-D filtered backprojection algorithm, yields 3-D images with cubic voxels. The spatial resolution of the detector was experimentally measured. For the application to bone investigation, the voxel size was set to 6.65 microm, and the experimental spatial resolution was found to be 11 microm. The reconstructed linear attenuation coefficient was calibrated from hydroxyapatite phantoms. Image processing tools are being developed to extract structural parameters quantifying trabecular bone architecture from the 3-D microCT images. First results on human trabecular bone samples are presented.

New prospects in CT image processing via mathematical morphology.

New prospects are foreseen in CT image processing via mathematical morphology (M.M.). M.M. is a set theory based upon the concept of "structuring elements" and allows texture analysis and pattern recognition by performing sequences of neighborhood transformations. This results in a wide range of quantifications. Mathematical morphology applied to CT densitometry allows obtaining the mean density of an organ after its automatic extraction from the background. This operation eliminates the approximations due to the manual selection of the Region of Interest (ROI). Precision, reliability and reproducibility are therefore improved. In this study, we performed the automatic isolation of a sole vertebral body in thoracic or abdominal CT slices to quantify numerous parameters, among them, density of the vertebral trabecular and cortical bones. On scans of the second and third metacarpals, morphomathematical analysis allowed quantification of the parameters of bone evolution: mean cortical density, directional cortico-diaphyseal index, and medullar area. In a different connection, M.M. has allowed automatic segmentation of lung parenchyma, the measurement of its mean density and the determination of the relative importance of the vascular network.

3D display of high resolution vertebral structure images.

In this paper we present a methodology for three-dimensional representation of vertebral structures. A set of X-ray CT images is obtained on a specific high resolution acquisition system. The images are then segmented in order to separate trabecular and cortical structures. Finally, the complex 3D surfaces are visualized using a volume rendering technique.

Experimental opacification of mediastinal lymph nodes by intraperitoneal injection of an iodinated fatty emulsion.

Absorption and lymphatic drainage of several lipiodol emulsions injected intraperitoneally have been studied in the rabbit and rat. Good opacification of the lymphatic channels and mediastinal lymph nodes is obtained in several hours with fine emulsions and in several days with coarse emulsions. The tolerance is related to dose, and the peritoneal reaction was moderate with the low doses, similar to that caused by the administration of physiologic saline alone. Computerized tomography in detecting low contrasts attained with small doses could render this method of indirect lymphography possible in man.

A method of radio-frequency inhomogeneity correction for brain tissue segmentation in MRI.

An automatic method of correcting radio-frequency (RF) inhomogeneity in magnetic resonance images is presented. The method considers that image intensity variation due to radio-frequency inhomogeneity contains not only low frequency components, but also high frequency components. The variation is regarded as a multiplication of low frequency (capacity variation of coil) and the frequency of object (true image). The efficiency of the proposed method is illustrated with the aid of both phantom and physical images. The impact of the inhomogeneity correction on brain tissue segmentation is studied in detail. The results show significant improvement of the tissue segmentation after inhomogeneity correction.

3D display of high resolution vertebral structure images.

A methodology for three-dimensional (3D) representation of vertebral trabecular structures was proposed. A set of X-ray CT images was obtained using a specific high resolution acquisition system. The images were then segmented in order to separate trabecular and cortical bone structures. Finally, the complex 3D surfaces were visualized using a volume rendering technique.

[Value and limitations of the computed x-ray tomographic measurement of vertebral mineralization]. / Intérêt et limites de la mesure tomodensitométrique de la minéralisation vertébrale.

An experimental study of the reproducibility and exactitude of densitometric measurements obtained by CT scanning showed: 1) the existence of marked variations due to factors related to the apparatus: beam energy, filtration, electronics, direction of rotation, reconstruction software; 2) that the structure of the object was also an influencing factor: variations in tissues surrounding the vertebra, and variations in bone density as a function of the plane in the vertebral body, and in fat content in the spongy tissue. Any measurement by CT scan of the mineral density of the vertebral body requires the use of a calibration phantom, strict definition of the volume to be measured, and routine correction for hypodensity induced by fat when necessary. Results under these conditions are reproducible and useful for the diagnosis of rarefying osteopathies.

[Measurement of vertebral bone density. Quantitative tomodensitometry or dual-photon absorptiometry?]. / Mesure de la densité osseuse vertébrale. Tomodensitométrie quantitative ou absorptiométrie biphotonique?

We have compared vertebral bone density measurements (QCT and DXA) in women in the postmenopausal period who underwent both examinations. Our aim was to study the results and to define the respective indications of QCT and DXA in various clinical pictures of osteoporosis. The subjects of the study were distributed into various groups according to the presence or absence of vertebral collapse and/or peripheral fractures. The results of the measurements were expressed as Z-scores (deviation from age-normal average) to suppress the age effect and to make comparison between both methods possible. The values of both measurements are significantly lower in case of vertebral involvement. QCT is more sensitive than DXA to discriminate vertebral collapse. A vertebral fragility threshold was defined at a Z-score of -1 with DXA and -1.25 with QCT, corresponding to the best sensitivity for an acceptable specificity. The results of densitometry suggest that there is a peripheral osteoporosis, different from vertebral osteoporosis, as early as the postmenopausal period. Since DXA is easy to implement, it can be used to screen osteoporosis. When the vertebral measurement with DXA is normal although osteoporosis is obvious (previous collapse or fracture), QCT must be used as it is more sensitive.

[An experimental study to evaluate mineralization of vertebral bone by computerized tomography (author's transl)]. / Evaluation de la minéralisation osseuse vertébrale par tomographie computérisée. Etude expérimentale.

Computerized tomography ("tomodensitometry") should, in principle, be able to calculate the linear attenuation coefficient of a compact or spongy bone volume. This coefficient is related to the amount of mineralization, enabling the use of the Scanner X to measure the density of the bone. Thirty vertebrae from the vertebral columns of 14 subjects who died after acute infections were examined by C.T. and by standard methods, and then calcinified. The correlation between ashes weight-Houns-field number was positive but only moderate (r = 0.54), and lower than the result obtained (r = 0.84) with standard methods. Errors occur with presently used apparatuses which are related to: polychromatism, too high an energy of the beam, artefacts, and the effects of "partial volume". Futhermore, the mineral concentration by unit of vertebral volume is very low, and large variations must occur for it to be detectable. Finally, considerable errors arise from the intravertebral bone fat. Suggestions are made with the objective of improving the quality of C.T. as a measuring instrument.

Micro-CT examinations of trabecular bone samples at different resolutions: 14, 7 and 2 micron level.

Tomographic techniques are attractive for the investigation of trabecular bone architecture. Using either conventional X-ray sources or synchrotron sources currently allows the acquisition of 3D images in a wide range of spatial resolution that may be as small as a few micrometers. Since it is technically possible to examine trabecular architecture at different scales, a question is to know what type of information it is possible to get at each scale. For this purpose, a series of ten vertebrae samples from healthy females of different ages (33 to 90) was imaged at various resolutions on three different micro-CT systems (cubic voxel size respectively 14, 6.7 and 1.4 microm). The comparison of morphometric parameters extracted from the different images is in agreement with simulation results on the influence of spatial resolution on structure parameters. The conclusion is that a 14 microm voxel size gives a reasonably good parameterisation of trabecular architecture. Besides the synchrotron radiation 2 microm level images reveal interesting features on the irregularities and rupture of trabecular surface, and on remodeling zones.

[Quantitative vertebral x-ray computed tomography. Results in 105 women consulting for osteoporosis]. / Tomodensitométrie vertébrale quantitative. Résultats sur 105 femmes consultant pour ostéoporose.

Quantitative vertebral CT scan imaging is a method developed to provide direct measurements of mineralization of vertebral body spongy tissue, and is presently the most precise procedure for the early detection of spinal osteoporosis. A fracture threshold has been defined below which are found 95% of patients with a crushed vertebra: it is situated at 70% of the value for mineralization normal for the age of patients. Patients with marked reductions in their level of mineralization can be kept under surveillance before the onset of fracture. In patients with vertebral collapses the density is correlated significantly with the number of crush fractures. In addition, measurement of vertebral spongy bone density has allowed the importance of the vertebral lesion to be determined in various osteoporotic disorders, including those with only cortical fractures, and in this way to differentiate them.

Multicentre European COMAC-BME study on the standardisation of bone densitometry procedures.

26 European centres participated in a concerted research action Biomedical Engineering: Quantitative Assessment of Osteoporosis. With a newly designed European spine and forearm phantom, the stability, accuracy, precision of dual energy absorption (DXA) and quantitative computer tomography (QCT) densitometry machines have been evaluated. Marked and clinically significant differences were found between brands and between techniques. Cross-calibration formulae have been made and normative data evaluated for different regions (spine, femoral neck, femoral trochanteric and forearm). A general fit for all data obtained from different machines was established.The cross-calibration formulae will allow a sensitivity analysis to assist the choice of equipment for clinical management of different categories of patients with bone disease. The present results obtained with an internationally accepted European spine and forearm phantom can now serve to stimulate the manufacturers to improve the comparability of bone measurements between machines.

Automatic quantification of vertebral cancellous bone remodeling during aging.

Anatomical transformation changes in vertebral spongy bone were quantified by automatic image analysis of microradiographs of 1 mm-thick sagittal slices from autopsied normal lumbar vertebrae (24 men and 28 women, age 35 to 96). Over a period of four decades, aging bone loss is 60% in women and 45% in men in the center of the vertebral body. With age, there is a new distribution of trabeculae: weight-bearing ones are twice (in young people) to six times (in old people) more numerous than transverse ones (measured on a sagittal slice). In the elderly, intertrabecular spaces enlarge while the proportion of the thinnest trabeculae increases.