Medical CT Research Articles

3D IMPRESS vision expert system for automated construction of three‐dimensional image processing procedures and its performance evaluation

AbstractThis paper considers feature extraction from a 3D gray level image and discusses the 3D IMPRESS system, which automatically constructs the 3D image processing procedure needed in the extraction, when the image feature to be extracted is directly specified in the form of a 3D figure (sample figure). The system is based on the fundamental idea of the IMPRESS 2D image processing expert system, which was developed by the authors, extending the components of the system to the 3D case. In this paper, the basic principle of the system is first described. Then a method is presented that automatically constructs the extraction procedure for the given sample figure. A method is discussed in which a more versatile procedure is derived from a large number of constructed procedures. Finally, the proposed system is used to extract various areas from a medical CT image, demonstrating that the procedure is satisfactory. © 2001 Scripta Technica, Syst Comp Jpn, 32(4): 25–37, 2001

Frequency domain volume rendering by the wavelet X-ray transform

We describe a wavelet based X-ray rendering method in the frequency domain with a smaller time complexity than wavelet splatting. Standard Fourier volume rendering is summarized and interpolation and accuracy issues are briefly discussed. We review the implementation of the fast wavelet transform in the frequency domain. The wavelet X-ray transform is derived, and the corresponding Fourier-wavelet volume rendering algorithm (FWVR) is introduced, FWVR uses Haar or B-spline wavelets and linear or cubic spline interpolation. Various combinations are tested and compared with wavelet splatting (WS). We use medical MR and CT scan data, as well as a 3-D analytical phantom to assess the accuracy, time complexity, and memory cost of both FWVR and WS. The differences between both methods are enumerated.

Quantitative analysis of reservoir rocks by microfocus X-ray computerised tomography

Abstract Microfocus Computer Tomography (μCT) is a non-destructive imaging technique that allows visualisation of internal features within non-transparent objects such as sedimentary rocks. With resolution as good as 10 μm in three dimensions, this technique is highly superior to medical CT widely used in geology and material sciences. Superior resolution is achieved by decreasing the X-ray spot size, which allows a decrease in the penumbra effect and an increase in primary magnification by placing the sample close to the X-ray source. Since polychromatic X-ray sources are used, the technique is not free of artefacts. Application of filtering techniques is recommended to circumvent these artefacts and to achieve good quality images for quantitative analysis. Application of a dual energy approach allows quantification of density as well as effective atomic number distribution of internal features. As the technique acquires data in 3D, μCT provides an ideal tool to link 2D thin-section petrography to 3D petrophysical measurements or to be used within an upscaling approach. A number of applications and the use of dual energy density and effective atomic number characterisations are presented. Attention is also paid to some of the limitations of this technique.

Quantitative evaluation of attenuation contrast of minerals by using a medical X-ray CT scanner.

Quantitative evaluation of attenuation contrast of minerals by using a medical X-ray CT scanner.

Three-dimensional observations of faulting process in Westerly granite under uniaxial and triaxial conditions by X-ray CT scan

Observations of spatial fault development in granite undergoing compression provide new insights into the process of faulting. Dry intact Westerly granite samples were loaded under a confining pressure of 100 MPa (triaxial conditions) and 5 MPa (∼ uniaxial conditions), and the progress of faulting was controlled by maintaining the increment of circumferential displacement at a constant rate, which apparently stiffened the machine. The samples were unloaded after they experienced some degree of stress drop and were successfully recovered before faulting progressed further. A conventional medical X-ray CT scanning system was used to image the sample interiors. Three-dimensional fault systems were detected with sequential X-ray CT images. It was found that three-dimensional reconstruction by X-ray CT images yields not only three-dimensional images of the fault system, but also provides fault cross-section images with much less artificial noise (artifacts) than does direct X-ray CT imaging. Three-dimensional images show that a fault system that developed under uniaxial conditions is much more complicated than a fault system produced by triaxial conditions. In addition, the fault plane produced under uniaxial conditions is inclined at a lower angle to the maximum compressive axis than under triaxial conditions. Comparing X-ray CT images, we show that a fault nucleates locally on the sample surface just after peak stress, then develops into the final fault plane in the residual stress stage of the complete stress–strain relationship under triaxial conditions.

Photostimulable storage phosphor image acquisition: Evaluation of three commercially available state-of-the-art systems

Photostimulable storage phosphor (PSP) image acquisition systems have been available for several years. The technology has had the opportunity to mature; however, there has not been an independent comparison of recently marketed commercial systems. For this study, three computed radiography (CR) systems using PSP technology (Kodak CR System 400 with autoloader [Eastman Kodak, Rochester, NY], Fuji FCR AC-3CS [Fuji Medical Systems, Stamford, CT], and Agfa ADC Compact [Bayer Corp, Ridgefield Park, NJ]) were connected to an IBM RadWorks diagnostic radiology workstation (IBM Corp, White Plains, NY) and evaluated for conformance to their performance specifications using guidance provided in the most recent draft acceptance testing protocol from Task Group No. 10, American Association of Physicists in Medicine. In addition, the physical requirements (e.g., space and power) and connectivity to another manufacturer's diagnostic workstation were examined. X-ray technologist comfort with each PSP imaging system and an assessment by our supporting biomedical equipment maintenance activity of their ability to service each PSP imaging system were also considered.

Caspase-mediated Cleavage of DNA Topoisomerase I at Unconventional Sites during Apoptosis

Previous studies have demonstrated that topoisomerase I is cleaved late during apoptosis, but have not identified the proteases responsible or examined the functional consequences of this cleavage. Here, we have shown that treatment of purified topoisomerase I with caspase-3 resulted in cleavage at DDVD146 downward arrowY and EEED170 downward arrowG, whereas treatment with caspase-6 resulted in cleavage at PEDD123 downward arrowG and EEED170 downward arrowG. After treatment of Jurkat T lymphocytic leukemia cells with anti-Fas antibody or A549 lung cancer cells with topotecan, etoposide, or paclitaxel, the topoisomerase I fragment comigrated with the product that resulted from caspase-3 cleavage at DDVD146 downward arrowY. In contrast, two discrete topoisomerase I fragments that appeared to result from cleavage at DDVD146 downward arrowY and EEED170 downward arrowG were observed after treatment of MDA-MB-468 breast cancer cells with paclitaxel. Topoisomerase I cleavage did not occur in apoptotic MCF-7 cells, which lack caspase-3. Cell fractionation and band depletion studies with the topoisomerase I poison topotecan revealed that the topoisomerase I fragment remains in proximity to the chromatin and retains the ability to bind to and cleave DNA. These observations indicate that topoisomerase I is a substrate of caspase-3 and possibly caspase-6, but is cleaved at sequences that differ from those ordinarily preferred by these enzymes, thereby providing a potential explanation why topoisomerase I cleavage lags behind that of classical caspase substrates such as poly(ADP-ribose) polymerase and lamin B1.

Medical rapid prototyping and 3D CT in the manufacture of custom made cranial titanium plates

This report describes a new method of custom making cranial titanium plates for the repair of skull defects. We have combined 3D CT imaging and surface modelling with rapid prototyping (RP) technology to produce physical models of our patients' skulls from which custom titanium plates were made. We have expanded the use of image processing tools applied to the CT image data to fabricate a representation of the skull defect. Medical RP models are relatively expensive and particular attention has been paid to developing image processing methods to reduce costs. Our technique used the patient as their own model and generated data from the contralateral side of the head where appropriate. We present the results of 10 patients who have had a custom made cranial titanium plate fitted and discuss the models for these cases. The benefits of our custom made titanium plates are reduced patient attendances to hospital and a more accurate titanium plate which has improved fitting and cosmesis.

Efficient Skeletonization of Volumetric Objects.

Skeletonization promises to become a powerful tool for compact shape description, path planning, and other applications. However, current techniques can seldom efficiently process real, complicated 3D data sets, such as MRI and CT data of human organs. In this paper, we present an efficient voxel-coding based algorithm for Skeletonization of 3D voxelized objects. The skeletons are interpreted as connected centerlines. consisting of sequences of medial points of consecutive clusters. These centerlines are initially extracted as paths of voxels, followed by medial point replacement, refinement, smoothness, and connection operations. The voxel-coding techniques have been proposed for each of these operations in a uniform and systematic fashion. In addition to preserving basic connectivity and centeredness, the algorithm is characterized by straightforward computation, no sensitivity to object boundary complexity, explicit extraction of ready-to-parameterize and branch-controlled skeletons, and efficient object hole detection. These issues are rarely discussed in traditional methods. A range of 3D medical MRI and CT data sets were used for testing the algorithm, demonstrating its utility.

APPLICATION OF X-RAY CT FOR DETECTION OF PHYSICAL FOREIGN MATERIALS IN FOODS

A medical X-ray CT scanner was used as a non-destructive inspection method for the detection of selectednon-metallic materials embedded in various fluids and food materials. The X-ray absorption characteristics of testedmaterials were expressed as X-ray CT numbers. It was found that the CT number of a foreign object was affected by asystemic error (a point spread function), even if its size was greater than 1 pixel in the video image provided by thescanner. Within the interface region between the foreign object and its surrounding matrix, CT numbers were found tovary smoothly between characteristic values for the object and the matrix thus pointing to important effects to considerwhen developing X-ray CT techniques for the detection and identification of foreign materials in foods. Specific thresholdvalues for CT numbers of selected foodstuffs were defined for successful detection of foreign materials. This study alsopointed out the limitation of using X-ray linear absorption coefficients from typical CT systems to detect certaincombination of foreign materials and foodstuffs.

A population study of apoE genotype at the age of 85: relation to dementia, cerebrovascular disease, and mortality

OBJECTIVESTo study the association of apoE genotypes with dementia and cerebrovascular disorders in a population based sample of 85 year old people.METHODSA representative sample of 85 year old people (303...

Pore level imaging of fluid transport using synchrotron X-ray microtomography

Recently developed high resolution computed microtomography (CMT) using synchrotron X-ray sources is analogous to conventional medical CT scanning and provides the ability to obtain three-dimensional images of specimens with a spatial resolution on the order of micrometers. Application of this technique to the study of core samples has previously been shown to provide excellent two- and three- dimensional high resolution descriptions of pore structure and mineral distributions of core material. Recently, computed microtomographic endpoint saturation images of a fluid filled sandstone core sample were obtained using a microtomographic apparatus and a high energy X-ray beam produced by a superconducting wiggler at the National Synchrotron Light Source at Brookhaven National Laboratory. Images of a 6 mm subsection of the one inch diameter core sample were obtained prior and subsequent to flooding to residual oil. Both oil and brine phases were observable within the imaged rock matrix. The rock matrix image data was used as input to a fluid transport simulator and the results compared with the end point saturation images and data. These high resolution images of the fluid filled pore space have not been previously available to researchers and will provide valuable insight to fluid flow, and provide data as input into and validation of high resolution porous media flow simulators, such as percolation-network and lattice Boltzmann models.

X-ray microtomography scanner using time-delay integration for elimination of ring artefacts in the reconstructed image

Most X-ray microtomography scanners work on the same principle as third-generation medical CT scanners, that is, the same point in each projection is measured by the same detector element. This leads to ring artefacts in the reconstructed image if the X-ray sensitivities of the individual detector elements, after any analytical correction, are not all identical. We have developed an X-ray microtomography scanner which uses the time-delay integration method of imaging with a CCD detector to average the characteristics of all the detector elements in each linear projection together. This has the added advantage of allowing specimens which are larger than the detector and X-ray field to be scanned. The device also uses a novel mechanical stage to “average out” inhomogeneities in the X-ray field. The results show that ring artefacts in microtomographic images are eliminated using this technique.

Cone beam X-ray microtomography for three-dimensional liberation analysis in the 21st century

A new method based on cone-beam X-ray microtomography is described for direct determination of the three-dimensional liberation spectrum of multiphase particles 100 microns in size or less. Such a technique may provide the basis for more detailed and accurate liberation analysis in the 21st century. Previous research had demonstrated the ability to use traditional medical X-ray CT scanners to determine the liberation spectrum of coarse coal particles of 1 cm in size (washability analysis). Rather than stacking a series of two-dimensional slices for volumetric imaging as is commonly done in traditional medical computed tomography, a three-dimensional reconstruction image array is prepared directly from the two-dimensional projections for cone beam geometry. The advantage of high spatial resolution (approximately 15 μm) with a microfocus X-ray generator combined with the benefit of direct processing of three-dimensional data, provide an excellent opportunity to overcome many of the limitations of current polished section techniques being used for the liberation analysis of multiphase particles.

Multiscale volume representation by a DoG wavelet

This article presents a method for decomposing volume data into 3D DoG (difference of Gaussians) functions by using the frame theory of nonorthogonal wavelets. Since we can think of a DoG function as a pair of Gaussian functions, we can consider this method an automatic generation of Blinn's blobby objects (1982). We can also use this representation method for data compression by neglecting the insignificant coefficients, since the wavelet coefficients have significant values only where the volume density changes. Further, since the DoG function closely approximates a /spl nabla//sup 2/G (Laplacian of Gaussian) function, the representation can be considered a hierarchy of the 3D edges on different resolution spaces. Using the spherically symmetric feature of the 3D DoG function, we can easily visualize the 3D edge structure by the density reprojection method. We apply our representation method to medical CT volume data and show its efficiency in describing the spatial structure of the volume.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Is rhythmic strain a growth factor for intestinal mucosa?: [formula omitted], G Li, F Hong, B Sumpio. Depts. of Surgery, Yale University Medical School, New Haven, CT & West Haven VA, West Haven, CT

Is rhythmic strain a growth factor for intestinal mucosa?: [formula omitted], G Li, F Hong, B Sumpio. Depts. of Surgery, Yale University Medical School, New Haven, CT & West Haven VA, West Haven, CT

Application of a Visualization Technique to Contouring Brain Substance in Medical CT Image

Application of a Visualization Technique to Contouring Brain Substance in Medical CT Image

Clostridial neurotoxins proteolyse individual members of an exocytotic fusion complex: H. Niemann,1S. Yamasaki,1T. Binz,1J. Blasi,2E. Link,2P. De Camilli,2T. Südhof3 and R. Jahn2 (1Department of Microbiology, Federal Research Center for Virus Diseases of Animals, P.O. Box 1149 D-72076 Tübingen, Germany; 2Cell Biology and Howard Hughes Medical Institute, Yale University Medical School, New Haven, CT, U.S.A.; and 3Department of Molecular Genetics and

Clostridial neurotoxins proteolyse individual members of an exocytotic fusion complex: H. Niemann,1S. Yamasaki,1T. Binz,1J. Blasi,2E. Link,2P. De Camilli,2T. Südhof3 and R. Jahn2 (1Department of Microbiology, Federal Research Center for Virus Diseases of Animals, P.O. Box 1149 D-72076 Tübingen, Germany; 2Cell Biology and Howard Hughes Medical Institute, Yale University Medical School, New Haven, CT, U.S.A.; and 3Department of Molecular Genetics and

PC-based surface reconstruction of medical CT Images

It is an active research area to reconstruct 3-D object and display its visible surfaces from cross-sectional images. In this paper, the methods of reconstructing 3-D object from medical CT images and displaying the visible surfaces are discussed. A polygon approximation method that forms polygon with the same number of segment points and a fast interpolation method for cross-sectional contours are presented at first. Then the voxel set of a human liver is reconstructed. And then the liver voxel set is displayed using depth and gradient shading methods. The software is written in C programming language at a microcomputer image processing system with a PC/AT computer as the host and a PC-VISION board as the image processing unit. The result of the processing is satisfying.

CT reconstruction algorithm for a dental panoramic X-ray unit

A variable Jacobian and weighted back projection algorithm, used for medical CT, was adapted to perform CT reconstructions on data obtained with a dental panoramic X-ray unit. A detector array, fitted to the unit for the purpose of acquiring digital panoramic radiographs, was used to collect the data. Compensations were made for the incomplete (230') rotation of the panoramic X-ray unit, the non-fixed centre of rotation, the irregular rotation of the X-ray target and detector, and the resulting variances in magnification. The algorithm was tested on mathematically simulated phantoms and on acquired data. Reconstruction of simulated data proved the success of the algorithm. Real data reconstructions showed some defects as a result of inaccuracies in quantifying the experimental panoramic device.