Segmentation of cancellous bone from high-resolution computed tomography images: influence on trabecular bone measurements.

The quantification of cancellous bone network from computed tomography (CT) images requires a segmentation step which is crucial and difficult because of the partial volume effect in CT images. In this paper, we present and evaluate a new approach for segmenting cancellous bone network from high-resolution CT (HRCT) slices. The idea is first to detect a skeleton from the crest lines of the structure and then to thicken it to extract the whole bone structure by satisfying local neighborhood constraints.

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.

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).

A comparison of spinal quantitative computed tomography with dual energy X-ray absorptiometry in European women with vertebral and nonvertebral fractures.

Quantitative computed tomography (QCT) was compared to dual X-ray absorptiometry (DXA) measured in the lumbar spine of 508 European women defined as normal without fracture (NoF), or osteoporotic (OP), with either vertebral fracture (VF), or peripheral fracture (PF). The correlations between QCT and DXA BMD measurements were significantly different in normal and in osteoporotic patients, indicating that the two exams do not measure the same bone aspects. According to ROC curves results, QCT Z-scores separate OP from NoF with better sensitivity than all other measurements.

CT of the middiaphyseal femur: cortical bone mineral density and relation to porosity.

Purpose: To determine whether computed tomography (CT) can be used to quantify age- and site-related changes in cortical bone mineral density (cBMD) at the middiaphyseal femur and whether cBMD differences are related to intracortical porosity.

Materials And Methods: Cortical bone specimens from 163 femurs were studied with CT and microradiography. Femurs were from 77 males and 86 females in a white anthropologic collection covering a broad age spectrum.

Perspectives in three-dimensional analysis of bone samples using synchrotron radiation microtomography.

In this paper we present a methodology based on 3D synchrotron radiation microtomography to analyze non-destructively 3D bone samples. After a technical presentation of the imaging system and the image analysis techniques, we report results on three-dimensional analysis of vertebral samples from women of different ages. The new capabilities of this technique for the investigation of bone are discussed.

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.

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.

Bone density reduction in various measurement sites in men and women with osteoporotic fractures of spine and hip: the European quantitation of osteoporosis study.

We have measured bone mineral density (BMD) using dual X-ray absorptiometry (DXA) of the spine and hip, spinal quantitative computed tomography (QCTspi), and peripheral radial quantitative computed tomography (pQCTrad) in 334 spine and 51 hip fracture patients. The standardized hip and spine BMD for each patient was calculated and compared with the combined reference ranges published previously, each densitometer having been cross-calibrated with the prototype European Spine Phantom (ESPp) or the European Forearm Phantom (EFP). Male and female fracture cases had similar BMD values after adjusting for body size, where appropriate.

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.

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.

European semi-anthropomorphic spine phantom for the calibration of bone densitometers: assessment of precision, stability and accuracy. The European Quantitation of Osteoporosis Study Group.

Up to now it has not been possible to reliably cross-calibrate dual-energy X-ray absorptiometry (DXA) densitometry equipment made by different manufacturers so that a measurement made on an individual subject can be expressed in the units used with a different type of machine. Manufacturers have adopted various procedures for edge detection and calibration, producing various normal ranges which are specific to each individual manufacturer's brand of machine. In this study we have used the recently described European Spine Phantom (ESP, prototype version), which contains three semi-anthropomorphic "vertebrae" of different densities made of stimulated cortical and trabecular bone, to calibrate a range of DXA densitometers and quantitative computed tomography (QCT) equipment used in the measurement of trabecular bone density of the lumbar vertebrae.

Dual-energy X-ray absorptiometry of the calcaneus: comparison with vertebral dual-energy X-ray absorptiometry and quantitative computed tomography.

The purpose of this study was to determine the efficacy of using bone mineral measurements of the calcaneus to evaluate osteoporosis. Dual energy X-ray absorptiometry (DXA) of the calcaneus was compared with posteroanterior lumbar absorptiometry (DXA) and vertebral quantitative computed tomography (QCT) measurements in 171 white women (78 normal and 93 osteoporotic). DXA measurement of os calcis mineralization decreased significantly in osteoporosis, but to a lesser extent than in vertebral sites.

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.

European semi-anthropomorphic phantom for the cross-calibration of peripheral bone densitometers: assessment of precision accuracy and stability.

A semi-anthropomorphic 'distal radius like' phantom, developed by Kalender and Ruegsegger for use in peripheral bone densitometry using single photon (DPA) dual X-ray (DXA) and quantitative computed tomography (QCT) machines, has been studied with a view to cross-calibrating different types and brands of densitometers in current use. In the context of an EU 'Concerted Action' (second Framework Programme) the phantom was repeatedly measured on six SPA machines, three DXA machines and nine QCT machines (545 measurements). Linear regression equations were derived, individual to each machine, which allowed the derivation of 'standardized densities'.

Factors influencing long-term in vivo reproducibility of QCT overtebral densitometry).

Objective: We investigated the long-term in vivo reproducibility of quantitative CT (QCT) examinations that were conducted in conformity with a standard and well established methodology.

Materials And Methods: The long-term reproducibility in vivo of QCT vertebral densitometry was studied in 12 normal postmenopausal women (mean age 51 years), who underwent four to five examinations over the same 2 year period.

Results: One group of six patients demonstrated good reproducibility with a coefficient of variation (CV) of bone mineral density (BMD) of < 2.

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.

[Contribution of medical imaging. What examinations for what indications?].

Osteoporosis is an obvious diagnosis in patients with fractures due to decreased bone mass. However, in many cases, major bone loss is infraclinical and requires quantification. Two methods are available to achieve this, i.

[Measurement of vertebral bone density. Quantitative tomodensitometry or dual-photon absorptiometry?].

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.

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.

CT image analysis of the vertebral trabecular network in vivo.

A method of computed tomography (CT) image analysis of lumbar vertebrae has been developed, providing a visualization of the trabecular network as it is represented in a 1.5 mm-thick CT image. We measured the length of the network and the number of discontinuities found in the image.

Measurement of anisotropic vertebral trabecular bone loss during aging by quantitative image analysis.

Age-dependent variations in the architecture of vertebral trabeculae in both the vertical and horizontal planes were characterized by quantitative image analysis. Images were obtained from autopsy specimens of the third lumbar vertebrae in 61 subjects (30 men and 31 women) whose ages ranged between 33 and 89 years). All subjects had died acutely either after trauma or illnesses unrelated to the skeleton.

[Contribution of microradiography in search of calcifications of valvular bioprostheses].

Implantation of a valvular bioprosthesis is one of the best treatments for valvular disease, particularly in children. Unfortunately, their use is limited as calcifications develop over time. Prevention of these calcifications is still an unresolved problem that is under study by Professor Carpentier and coworkers.

[Quantitative vertebral x-ray computed tomography. Results in 105 women consulting for osteoporosis].

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.