Microtomography System Research Articles

Micro-tomographic imaging for material sciences at BL47XU in SPring-8

A micro-tomographic system developed at BL47XU in SPring-8 (SP-μCT47XU) was used to obtain three-dimensional structures of synthetic and natural substances for a test study. Al 2 O 3 -YAG eutectic composites. synthetic quartzites (SiO 2 ) and Antarctic micro-meteorites (AMMs) were successfully imaged with the spatial resolution of 1μm three-dimensionally. Three-dimensional elemental distribution was also obtained using X-ray adsorption edge of Fe in the measurement of an AMM.

An X-ray micro-tomography system optimised for the low-dose study of living organisms

An X-ray micro-tomography system has been designed that is dedicated to the low-dose imaging of radiation sensitive living organisms and has been used to image the early development of the first few days of plant development immediately after germination. The system is based on third-generation X-ray micro-tomography system and consists of an X-ray tube, two-dimensional X-ray detector and a mechanical sample manipulation stage. The X-ray source is a 50 kVp X-ray tube with a silver target with a filter to centre the X-ray spectrum on 22 keV.A 100 mm diameter X-ray image intensifier (XRII) is used to collect the two-dimensional projection images. The rotation tomography table incorporates a linear translation mechanism to eliminate ring artefact that is commonly associated with third-generation tomography systems. Developing maize seeds ( Triticum aestivum) have been imaged using the system with a cubic voxel linear dimension of 100 μm, over a diameter of 25 mm and the root lengths and volumes measured. The X-ray dose to the plants was also assessed and found to have no effect on the plant root development.

Cone beam X-ray microtomography — a new facility for three-dimensional analysis of multiphase materials

As the techniques and resolution for three-dimensional spatial analysis have advanced in the last deauie, it is now possible to map in detail the microstructure ofmllltipizase materials in three-dimensional digital space. In this regard, three-dimensiollal X-ray microtomography offers a unique imaging capability. Sparial resolution on the order of lO pm can be achieved ,,'/ith the lise of microfocus X-ray generators. Recently, a state-oIfhe-art cone beam X-ray microtomography system was installed at the University of Utah for the quantitative analysis of multiphase materials in three dimensions. This facility was designed to obtain 2,048 by 2,048-pixel reconstruction overa lO-mm diameter, while also allowingfor the imaging of somewhat larger (40-mm) objects. The system is capable of handling high-density materials, even materials having a density as high as 8.0 glcm 3 . This ullique, one-of-a-kind instrument can he used to obtain three-dimensional spatial reconstruction for many applications, such as three-dimensional liberation analysis, pore structure analysis of particle beds during filtration and the air-void system of concrete structures. The utilization of X-ray microtomography not only allows for the quantitative analyst.\· of multiphase systems but also allows for the textural characterization and determination of phase continuity. This paper presents injomwtion regarding the current use of this new facility and a review of potential applications for the advanced analytical system.

Fast Algorithm for X-ray Cone-beam Microtomography.

Cone-beam X-ray microtomography attracts increasing attention due to its applications in biomedical sciences, material engineering, and industrial nondestructive evaluation. Rapid volumetric image reconstruction is highly desirable in all these areas for prompt visualization and analysis of complex structures of interest. In this article, we reformulate a generalized Feldkamp cone-beam image reconstruction algorithm, utilize curved voxels and mapping tables, improve the reconstruction efficiency by an order of magnitude relative to a direct implementation of the standard algorithm, and demonstrate the feasibility with numerical simulation and experiments using a prototype cone-beam X-ray microtomographic system. Our fast algorithm reconstructs a 256-voxel cube from 100 projections within 2 min on an Intel Pentium II(R) 233 MHz personal computer, produces satisfactory image quality, and can be further accelerated using special hardware and/or parallel processing techniques.

A 3-D X-ray microtomographic system with a CMOS image sensor

High-resolution and three-dimensional X-ray imaging is becoming more and more popular. An X-ray microtomographic system with a CMOS image sensor has been developed, We have developed a novel area X-ray detector with a cost-effective CMOS image sensor. The sensing area of the detector is 55/spl times/55 mm/sup 2/ and the light from the phosphor screen is collected to the CMOS image sensor by a carefully designed optical system. Six lenses are assembled to reduce the radiation damage effect and increase the resolution and sensitivity. A microfocus X-ray tube that can reach up to 5 /spl mu/m of focal spot size and microprecision motor system that can move in x-y-z directions for both alignment and magnification and rotate the object have been adopted. A conventional three-dimensional cone-beam Feldkamp reconstruction algorithm was used and a human cancellous bone has been imaged with this system. Currently, the resolution of this system is about 40 /spl mu/m but the application in microtomography seems very promising using this CMOS X-ray detector.

A high-throughput x-ray microtomography system at the Advanced Photon Source

A third-generation synchrotron radiation source provides enough brilliance to acquire complete tomographic data sets at 100 nm or better resolution in a few minutes. To take advantage of such high-brilliance sources at the Advanced Photon Source, we have constructed a pipelined data acquisition and reconstruction system that combines a fast detector system, high-speed data networks, and massively parallel computers to rapidly acquire the projection data and perform the reconstruction and rendering calculations. With the current setup, a data set can be obtained and reconstructed in tens of minutes. A specialized visualization computer makes rendered three-dimensional (3D) images available to the beamline users minutes after the data acquisition is completed. This system is capable of examining a large number of samples at sub-μm 3D resolution or studying the full 3D structure of a dynamically evolving sample on a 10 min temporal scale. In the near future, we expect to increase the spatial resolution to below 100 nm by using zone-plate x-ray focusing optics and to improve the time resolution by the use of a broadband x-ray monochromator and a faster detector system.

In vivo micro tomography.

The diagnosis of osteoporosis is challenging. Usually, the disease progresses slowly, and it is therefore difficult to detect osteoporosis early, or to document the progression of the disease and the effect of a treatment. Several researchers have observed that bone quality cannot be assessed reliably with bone density alone, and that bone microarchitecture has to be considered as well.1-4In spite of these findings, clinical diagnosis still relies almost exclusively on the measurement of bone density. Three-dimensional computed tomography offers a way out of this dilemma. Laib, Ruegsegger, et al. showed with a three-dimensionalin vivoCT scanner that bone structure provides valuable additional information on the skeleton.5,6In recent years, microtomography became an increasingly popular method to image complex structures with features in the micrometer range. A microtomographic system typically assesses a sample in 3D at high spatial resolution, and thus allows unobstructed visual access to the sample’s inner structure. Regardless of whetherin vivoorin vitromeasurements are to be performed, high spatial resolution is the prime factor guiding today’s CT scanner developments. Dose and scanning speed become important issues forin vivomeasurements. Since patient or subject movement have an adverse effect on image quality, the scanning speed ofin vivoCT systems has to be as short as possible.

Development of an osteoporosis animal model of the jaw area

The aim of the following study was to develop an osteoporotic model by means of ovariectomy. Bone mineral density of the upper and lower jaw was measured by dual energy X-ray absorptiometry (DPX) before and after ovariectomy. Histomorphometric measurements were done by a microtomography system. Bone mineral density decreased significantly after ovariectomy in the upper and lower jaw.

Early morphometric and anisotropic change in periarticular cancellous bone in a model of experimental knee osteoarthritis quantified using microcomputed tomography

Objective. To quantify early stage microstructural changes of periarticular cancellous bone in a canine anterior cruciate ligament transection model for experimental osteoarthritis. Design. Unilateral transection of the anterior cruciate ligament was performed in 10 animals. Bone structure changes were quantified in five animals at 3-week post-transection and five animals at 12-week post-transection. An additional two non-operated animals were used as controls. Background. Changes in trabecular architecture of the periarticular cancellous bone in early stage post-traumatic osteoarthritis is not well understood. Previous studies have found alterations in bone mineral density in experimental osteoarthritis suggesting adaptation of the trabecular structure. Early change of the periarticular bone following a ligament injury may contribute to the long-term development of osteoarthritis. Methods. Bone cores from the medial condyles of the femoral and tibial pairs were scanned with a three-dimensional microtomographic system. Structural indices were quantified including bone volume ratio, bone surface ratio, trabecular thickness, trabecular separation, trabecular number, as well as structural anisotropy determined by the mean-intercept-length method. Results. Significant structural changes were observed at 3-week post-transection, and were more prominent at 12-week post-transection. These changes were accompanied by decreasing anisotropy. Conclusions. Periarticular cancellous bone microstructure is significantly altered in experimental osteoarthritis. These changes occurred as early as 3-week post-transection, and were large at 12-week post-transection. Relevance The pathogenesis of post-traumatic osteoarthritis is poorly understood, but it is clear that this disease involves the entire organ system of the joint, including the cartilages, synovium, ligaments, and bones. This study focuses on the changes that occur in the bones during the early stages following a joint injury, and contributes to a better overall understanding of the disease aetiology.

A 3D microtomographic system with stacked fan-beam geometry

The move from 2D to 3D analysis, and the increase in spatial resolution characterize recent improvements in CT-based structure assessment. A new desktop micro-CT system with high scanning speed has been developed. The instrument makes use of a novel multiple fan-beam technique: radiation from a line-focus X-ray tube is divided into a stack of fan-beams by a foil collimator with a 30 μm pitch. The stacked fan-beam geometry allows to design compact CT scanners with a source-to-detector distance of only 18 cm. The complete system fits into a standard 19 in. rack. Image reconstruction is based on standard fan-beam algorithms, which eliminates the difficulties and limitations associated with cone-beam reconstruction. The detector comprises a low-noise area CCD sensor, a fiber-optic light guide and a scintillator screen. A complete examination requires 2 min only. The new micro-CT system has a voxel size of 20×20×26 μm 3. Each 3D image contains a quarter of a billion voxels or a multiple of it. Samples up to 20 mm in diameter and up to 40 mm in length can be imaged. The instrument can be operated in a normal lab environment.

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.

A multiple detector array helical x-ray microtomography system for specimen imaging.

An x-ray computed microtomography system for specimen and small animal imaging was built and tested. The system used seventeen 48-microm-wide detector arrays (a charge coupled device camera) and helical acquisition techniques. Images were acquired using 540 rays/view and 400 views/2pi. The modulation transfer function (MTF) of the computed tomography images demonstrated 50 microm limiting resolution, with MTF > 10% for objects larger than 60 microm (approximately 8.3 cycles/mm). While soft tissue discrimination was compromised by a low signal-to-noise ratio, equine medullary bone core samples and the murine skeleton were well visualized. The incorporation of multiple detector arrays provided a 17-fold improvement in x-ray efficiency, which is a very important step toward improving the potential of microtomography as a scientific tool.

Region-of-interest microtomography for component inspection

The authors describe a novel technique for the nondestructive evaluation of microelectronic components using X-ray microtomography. Existing microtomography systems have spatial resolution of order 1 /spl mu/m but require X-ray source brilliance that would become unachievable at higher resolutions. The authors describe an imaging method that reduces the number of X-ray photons required from the source without degrading the resolution. The feasibility of the technique is demonstrated through a series of computer simulations. The results are verified with real data from synchrotron experiments.

Micro-compression: a novel technique for the nondestructive assessment of local bone failure

Many bones within the axial and appendicular skeleton are subjected to repetitive, cyclic loading during the course of ordinary daily activities. If this repetitive loading is of sufficient magnitude or duration, fatigue failure of the bone tissue may result. In clinical orthopedics, trabecular fatigue fractures are observed as compressive stress fractures in the proximal femur, vertebrae, calcaneus and tibia, and are often preceded by buckling and bending of microstructural elements. However, the relative importance of bone density and architecture in the etiology of these fractures is poorly understood. The aim of the study was to investigate failure mechanisms of 3D trabecular bone using micro-computed tomography (microCT). Because of its nondestructive nature, microCT represents an ideal approach for performing not only static measurements of bone architecture but also dynamic measurements of failure initiation and propagation as well as damage accumulation. For the purpose of the study, a novel micro-compression device was devised to measure loaded trabecular bone specimens directly in a micro-tomographic system. The measurement window in the device was made of a radiolucent, highly stiff plastic to enable X-rays to penetrate the material. The micro-compressor has an outer diameter of 19 mm and a total length of 65 mm. The internal load chamber fits wet or dry bone specimens with maximal diameters of 9 mm and maximal lengths of 22 mm. For the actual measurement, first, the unloaded bone is measured in the microCT. Second, a load-displacement curve is recorded where the load is measured with an integrated mini-button load cell and the displacement is computed directly from the microCT scout-view. For each load case, a 3D snap-shot of the structure under load is taken providing 34 microm nominal resolution. Initial measurements included specimens from bovine tibiae and whale spine to investigate the influence of the structure type on the failure mechanism. In a rod-like type of architecture as seen in the whale spine, structural failure was described by an initial buckling and bending of structural elements followed by a collapse of the overloaded trabeculae. In the more plate-like bovine tibial architecture, buckling and bending could not be observed. Failure rather seemed to occur instantaneously. In conclusion, micro-compression in combination with 3D microCT allows visualization of failure initiation and propagation and monitoring of damage accumulation in a nondestructive way. We expect these findings to improve our understanding of the relative importance of density, architecture and load in the etiology of spontaneous fractures of the hip and the spine. Eventually, this improved understanding may lead to more successful approaches to the prevention of age-related fractures.

Evaluation of a microtomography system with an X-ray microfocus tube

The microfocus radiography system has been realized by means of a microfocus X-ray tube (maximum 160 kV), an image intensifier data collector and a five degree of freedom manipulation table. An 8-bit image acquisition PC-card and software were included to compose the microtomography system. To assemble the system, an image quantitative analysis was carried out by evaluation of the focal spot size, modulation transfer function of the system, and the ‘defect discernibility curves’. The 2D microtomographies were carried out using the mean of 10 image central lines in each projection. Image processing techniques were also used to obtain better results. The image reconstruction program is based on a filtered backprojection algorithm using a special window. Images of various types of samples were carried out in order to verify the performance of the system.

X-ray microtomography: Nondestructive three-dimensional imaging for in vitro endodontic studies

Article shows the application of a laboratory x-ray microtomography system, a miniaturized form of conventional computerized axial tomography, to the study of root canal morphologic characteristics and changes in the course of root canal treatment in extracted teeth. After reconstruction of the three-dimensional images, the IDL software package (Research Systems, Inc., Colorado) was used to obtain cross-sectional slices of the tooth and three-dimensional views of rendered surfaces of constant mineral density. The root canal systems and changes in these were imaged at a resolution (cubic voxel side-length) of ∼40 μm.

A microtomographic system for the nondestructive evaluation of bone architecture.

Microtomography (micro-computed-tomography, mu-CT) is a method to image and quantify trabecular bone. It has the capability to address the role of trabecular architecture on the mechanical properties of bone and to study trabecular bone remodeling. The system described in this work is based on a compact fan-beam type tomograph that can work in spiral scanning or multislice mode. An X-ray tube with a microfocus is used as a source, a CCD-array as a detector. Samples with diameters from a few millimeters to a maximum of 14 mm can be measured, typically, bone biopsies with a diameter of 8 mm and a length of approximately 10 mm are measured. Spatial resolution is 28 microns. Usually the volume of interest contains 4 x 4 x 4 mm3 and is represented in 14 x 14 x 14 microns3 voxels. 3D stereological indices are extracted according to the standard definitions used in histomorphometry. Triangular surface representation is effected with an extended marching cube algorithm and forms a convenient basis for finite element analysis. Microtomographic measurements may be employed to "calibrate" lower-dose, lower-resolution images in vivo as well as to nondestructively assess unprocessed surgical bone biopsy specimens. These specimens remain intact for mechanical or histological testing.

A Microtomographic System for the Nondestructive Evaluation of Bone Architecture

A Microtomographic System for the Nondestructive Evaluation of Bone Architecture

Microtomography using a tube source of X-rays, a low-energy-resolution HPGe detector system and an array of detectors

A new microtomographic system has been assembled with a geometrical resolution of about 25–50 mm. This system is employed directly using the bremsstrahlung radiation and filtering the primary radiation with absorbers composed by an element. A reconstruction programme, written in PASCAL is able to give the reconstruction matrix of linear attenuation coefficients, simulates the matrix and the related tomography. Microtomography was studied thoroughly with different samples like acrylic cylinders containing internal W-wires of about 10 μm diameter, acrylic cylinders with holes of known diameters, small pencils with internal graphite, acrylic cylinders containing grains of soil and so on.

Microfocus radiography producing microtomography

A microtomographic system has been made using a real time microfocus radiographic system and a image digitalizer schedule. The aim of this system was reaching an acceptable data acquisition time, which was hardly reduced compared to traditional microtomographic systems that employ conventional X-ray sources and detectors. Several microtomographs were made using the same type of samples used in these traditional systems, in order to compare the performance of the our system (spatial resolution, density resolution and image quality).