CT Image Processing Research Articles

Post- Impact Fatigue Damage Analysis of Quasi Isotropic CFRP Laminates through Infrared Thermography

Carbon fiber reinforced plastic (CFRP) materials used for lightweight aircraft structures are susceptible to low velocity accidental impacts during manufacture and while in service. In this study the CFRP laminates subjected to low velocity impact conditions of three different energy levels were tested under various fatigue loading conditions till it reached the failure state. The infrared thermography NDT technique was used for the damage analysis of these post-impact fatigue loaded CFRP specimens to understand the damage distribution across the specimen. The cooling response curves obtained from the active thermography of the post impact fatigue specimens under four different combinations (transmission or reflection mode with impacted or un-impacted surface facing camera) for each of the specimens were analyzed. The rate of cooling in the temperature response curves is different for each specimens subjected with various post impact-fatigue loading conditions and it seems to be correlated with the extent of post-impact fatigue damage present in each specimen quantified through X-ray CT image processing. The temperature rise observed in the passive thermography at the fiber/ply breakage during static strength tests were proportional to corresponding load drops and the non-homogeneous spread of damage at the onset of tensile failure was seen from the thermographs.

An investigation on the three-dimensional transport of chloride ions in concrete based on X-ray computed tomography technology

In order to demonstrate the three-dimensional chloride ions diffusion in real concrete, the X-ray CT technique was applied to reconstruct the meso- and micro-structure of concrete. An improved threshold method was used to eliminate the noise during X-ray CT images processing. The special distribution of aggregate particles and pores were recognized and analyzed based on the reconstructed meso-structure of real concrete. The reconstructed meso-structure, as well as the interfacial transition zone (ITZ) were introduced into a multi-phase model to numerically characterize the three-dimensional diffusion of chloride ions in real concrete. And the simulation results were verified through electron probe technique. A parameter sensitivity analysis was conducted to furtherly assess the influence of ITZ diffusivity on the chloride ions diffusion in concrete. This investigation indicates that aggregate particles tends to deposit at the bottom of the specimen and the pores are likely to concentrate at the top part. Due to the special distribution of aggregate particles and pores, the chlorides ions diffuse more quickly at the bottom of the specimen. The study proves that the aggregate particles, pores and ITZ are of great importance for the three-dimensional chloride ions diffusion in real concrete.

Research on the Development Mechanism of Postpeak Cracks in Sandstone under Different Confining Pressures

Water inrush happens occasionally during deeper roadways excavation. It is mainly due to the lack of understanding in the formation and development mechanism of cracks and its spatial distribution pattern under ground stress. In view of this, this paper used different stress levels to represent the fracture state of different parts of the surrounding rock of the deep roadway; CT detection technique is used to scan the fractured sandstone in the postpeak state; and the CT images under different confining pressures are thus obtained. The geometrical parameters such as area, length, and width of the crack are used to describe the distribution patterns based on CT images processing technique and statistical principle. These patterns are then analyzed under varying postpeak stress levels and confining pressures. The result shows that, as the area, length, and width of the cracks get larger, number of cracks increases with decreasing stress level; at different stress levels, sandstone crack area probability density, crack length probability density, and crack width probability density form exceptional, linear, and Gaussian distribution, respectively. The amount of confining pressure affects the size of cracks and the extent of expansion. This means that the higher the confining pressure is, the easier the internal crack will be penetrated and expanded and the bigger the cracks are, and the number of cracks gets lesser. Such research results can be used to describe the propagation and evolution law of cracks under different stress states of postpeak rock, which also provide an important basis for further analysis of its permeability and the stability of roadway surrounding rock.

Experimental investigation on the effect of pore characteristics on clogging risk of pervious concrete based on CT scanning

Abstract Pervious concrete is one of the permeable pavement materials, which can improve the traffic safety and road environment. However, the clogging problem of pervious concrete is considered as a potential common deficient of the permeable pavement that causes severe loss of the ecological function. Generally, the main cause of clogging is the interlocking of the pores with clogging particles. Therefore, addressing the problem of clogging needs to explore the influence of pore characteristics and clogging particles on the pervious concrete. This study determined the equivalent diameter of pores through CT scanning and image processing using an algorithm code to calculate the geometry properties of the open and closed pores. Moreover, the variation of permeability after clogging has been analyzed. The experimental results showed that the pore size could determine whether clogging particles can block or pass through the pores or not, which is closely related to the clogging degree. Finally, the new findings can help engineers and designers to optimize the design of pervious concrete to forwardly avoid or mitigate the clogging problem, which has a promising realistic signification for permeable pavement design and maintenance.

Method of Threshold CT Image Segmentation of Skeletal Bones

Background . Segmentation of images in the existing application software does not adequately separate the background area qualitatively, the allocation of anatomical structures, in particular skeletal bones, is partial with a significant number of artifacts, which are complicating further 3D modeling. Objective. The aim of the paper is development of the technique for automatized CT images segmentation of skeletal bones. Methods. The CT images of bone were segmented based on the developed algorithm, which included: threshold segmentation; morphological transformations of the unbound domains connections, the distance between them does not exceed the set value; the filling of areas with zero values, which are separated by pixels with values 1; comparison of segmentation results for neighboring sections. Testing techniques for segmentation multi-cut CT image of the patient with heterotopic ossification of the hip joints were analyzed. Segmentation results were compared with the images processed by specialists. The criteria for quality of segmentation were errors of the first and second kind: true-positive, true-negative, false-negative, false-positive voxels that were marked. Results. The developed algorithm for automatized segmentation of skeletal bones according to CT data shows 22% more qualitative results of research objects selection compared to usual threshold method; segmentation error was less than 8%. Calculated values of specificity were 99.9%, accuracy – 99.8%, sensitivity – 92.5% and for threshold method – 99.9%, 99.3%, and 70.7% respectively. Conclusions. The obtained results significantly reduce the time of CT images processing by a specialist in the area of radiation diagnostics and 3D printing of biological tissues and their models. Future prospects for the proposed methodology development are: its integration into specialized software tools with a user interface with a wide range of tools; improvement of machine code, reducing of computer time calculations; improvement of the segmentation algorithm, reducing of the segmentation artifacts.

Research on establishing numerical model of geo material based on CT image analysis

Geotechnical engineering material is a kind of heterogeneous composite material. The stone, mineral, gravel, hole, and crack contained in it have different physical and mechanical properties, and their responses to external forces are very different. For example, stress distribution, crack propagation, and failure mode are closely related to material heterogeneity and microstructure. This paper presents a finite element model method for processing CT images of geotechnical materials by using digital image technology. This paper presents a finite element model method for processing CT images of geotechnical materials by using digital image technology. The theory of digital image processing is applied to geotechnical CT image processing to realize pseudo-color enhancement of CT image, and the histograms of different geotechnical CT numbers are obtained. Canny operator is used to detect the edge of geotechnical CT image, and the binary image of geotechnical microstructure is obtained. According to the color change of pseudo-color enhanced image and CT histogram, the meso-structure and variation of rock and soil can be quantitatively analyzed. The finite element model established by this method can fully consider the heterogeneity of geotechnical materials, especially the effect of void distribution on the mechanical properties of geotechnical materials.

Developments in Segmentation of Abdominal Liver CT Images for Cancer and Other Disease Lesion Detection

Segmentation is one of the most important and widely used methods in medical image analysis. It is considered to be a high level image processing technique and can be used for many applications in medical imaging. CT images are commonly used in medical field and it provides clear picture of the internal organs. However in some places further processing of CT images are required for disease diagnosis and lesion detection. This work is an effort for bringing out clinical information from liver images of computed tomography based on image processing. Finally liver tumor classifications have been performed using texture based image analysis.

Tensor Voting Based Vascular Bifurcation Detection in CT Images of Lung

The accurate detection of vascular bifurcations is not helpful for pulmonary vascular disease diagnosis, but vital in (Computed Tomography) CT image analysis and processing of lung. We propose a tensor voting based method for vascular bifurcation detection in CT image of lung, which a vessel enhancement method is firstly proceeding to initially extract vessel structure, on which we perform ball voting with the pixels.

An Edge Detection Method for Suspicious Local Regions in CT images with Jaxtapleural Nodules

Juxtapleural lung nodules are often excluded from the lung region in many CT image processing algorithms which are based on intensity information. For solving this problem, a suspicious edge line detection algorithm is proposed to obtain the edge line of the suspicious local lung region in this manuscript. Firstly, the lung region in the CT image is extracted by a fixed threshold. Then a SIFT algorithm is used to detect the feature point in the lung region. To filter out the useless feature points, a closest point matching method is used. Then a K-mean method is introduced to divide those feature points into several parts in which the edges of juxtapleural Lung nodules are contained. Experiments over CT slices show that the proposed method has a great performance in detecting the edge line of suspicious regions.

Post mortem CT of intrahepatic gas distribution in twenty-seven victims of a flood: Patterns and timing.

We reported the results of post mortem computed tomography of the liver in 27 subjects dead simultaneously during a flood. The aim of our work was to identify the different patterns of post mortem intrahepatic gas distribution and the timing of its appearance. Although post mortem CT is the method of choice for the evaluation of gas distribution, controversies exist about the first site of appearance of intrahepatic gas (portal veins versus hepatic veins) as well as the timing and steps of intrahepatic gas spreading. In each subject we performed thin slice CT scanner (Somatom Definition, Siemens) and post processing of native CT images with Minimum Intensity Projection technique. Our results show that the first site of appearance of intrahepatic gas is portal veins. Gas in hepatic veins was never seen without the presence of the gas in portal vein. Gaseous cysts in hepatic parenchyma represent a further and usually more tardive pattern of intrahepatic gas distribution. In addition, we demonstrated that differences in timing of gas spreading was statistically significative for exclusive presence of portal veins gas before 48h as well as for complete substitution of hepatic parenchyma by cysts 64h after death. In conclusion, our work shows that the CT study of postmortem intrahepatic gas distribution could be a useful complementary tool both in demonstrating the mechanism of intrahepatic gas spreading and in estimating post mortem interval.

Pore-scale investigation of microscopic remaining oil variation characteristics in water-wet sandstone using CT scanning

With the aid of CT scanning and image processing techniques, water displacing oil experiments were performed to analyze six natural water-wet sandstone cores of different permeability and porosity visually and quantitatively. Microscopic remaining oil was categorized on the basis of quantitative characterization parameters, such as shape factor, contact ratio, Euler number etc. The remaining oil characteristics with different flow types were presented in different water displacement stages. Experimental results show that the remaining oil can be divided into five categories. They are, respectively membranous flow, droplet flow, columnar flow, multi-porous flow and clustered flow from hard-to-produce to easy-to-produce. The relative permeability of oil phase is represented by the macro-average relative permeability of all the above five flow regimes. Among them, clustered flow possesses strong producing capacity and high relative permeability, and the other four flow regimes have weaker producing capacity and lower relative permeability. Variation of number and average volume of five types remaining oil and several measurements of the ganglion size distribution have been performed in the literature. The nonlinear knee point on the relative permeability ratio curve is intrinsically caused by the decreasing of volume and quantity fraction of clustered flow when water saturation increases. This paper has studied the flowing law of microscopic remaining oil, explained the intrinsic mechanism for the appearance of an inflection point on the relative permeability ratio curve and microscopic sweep phenomena, and also presented a new effective way of upscaling to a certain extent.

GW27-e0955 Quantification of coronary flow using dynamic angiography with 320-detector row CT and motion coherence image processing: Detection of ischemia for intermediate coronary stenosis

GW27-e0955 Quantification of coronary flow using dynamic angiography with 320-detector row CT and motion coherence image processing: Detection of ischemia for intermediate coronary stenosis

Learning-Based Artifact Removal via Image Decomposition for Low-Dose CT Image Processing

Streak artifacts and mottle noise often appear in low-dose CT (LDCT) images due to excessive quantum noise in low-dose X-ray imaging process, thus degrading CT image quality. This research is aimed at improving the quality of LDCT images via image decomposition and dictionary learning. The proposed method first decomposes a LDCT image into the low-frequency (LF) and high-frequency (HF) parts by a bilateral filter. The HF part is then decomposed into an artifact component and a tissue component by performing dictionary learning (DL) and sparse coding. The tissue component is combined with the LF part to obtain the artifact-suppressed image. At last, a DL method is applied to further reduce the residual artifacts and noise. Different from previous research works with sparse representation, the proposed method does not need to collect training images in advance. The results of numerical simulation and clinical data experiments indicate the effectiveness of the proposed approach.

Renal applications of dual-energy CT.

Dual-energy CT is being increasingly used for abdominal imaging due to its incremental benefit of material characterization without significant increase in radiation dose. Knowledge of the different dual-energy CT acquisition techniques and image processing algorithms is essential to optimize imaging protocols and understand potential limitations while using dual-energy CT renal imaging such as urinary calculi characterization, assessment of renal masses and in CT urography. This review article provides an overview of the current dual-energy CT techniques and use of dual-energy CT in renal imaging.

Quantification of coronary flow using dynamic angiography with 320-detector row CT and motion coherence image processing: Detection of ischemia for intermediate coronary stenosis

ObjectivesAnatomical coronary stenosis is not always indicative of functional stenosis, particularly for intermediate coronary lesions. The purpose of this study is to propose a new method for quantifying coronary flow using dynamic CT angiography for the whole heart (heart-DCT) and investigate its ability for detecting ischemia from intermediate coronary stenosis. MethodsParticipants comprised 36 patients with coronary artery disease who underwent heart-DCT using 320-detector CT with tube voltage of 80kV and myocardial perfusion scintigraphy (MPS). Heart-DCT was continuously performed at mid-diastole throughout 15–25 cardiac cycles with prospective ECG-gating after bolus injection of contrast media (12–24ml). Dynamic datasets were computed into 90–100 data sets by motion coherence image processing (MCIP). Next, time-density curves (TDCs) for coronary arteries with a diameter >3mm were automatically calculated for all phases using MCIP. On the basis of the maximum slope method, coronary flow index (CFI) was defined as the ratio of the maximum upslope of coronary artery attenuation to the upslope of ascending aorta attenuation on the TDC, and was used to quantify coronary flow. CFIs for the proximal and distal sites of coronary arteries with mild-to-moderate stenosis were calculated. Coronary territories were categorized as non-ischemic or ischemic by MPS. Receiver-operating-characteristic (ROC) analysis was performed to determine the optimal cutoff for CFI to detect ischemia. ResultsDistal CFI was significantly lower for ischemia (0.26±0.08) than for non-ischemia (0.50±0.17, p<0.0001). No significant difference in proximal CFI was seen between ischemia (0.55±0.23) and non-ischemia (0.62±0.24). ROC analysis revealed 0.39 as the optimal cutoff for distal CFI to detect ischemia, with C-statistics of 0.91, 100% sensitivity, and 75% specificity. ConclusionsThis novel imaging technique allows coronary flow quantification using heart-DCT. Distal CFI can detect myocardial ischemia derived from intermediate coronary stenosis.

A No-Reference Image Quality Metric with Application in Low-Dose Human Lung CT Image Processing

In this paper a no-reference image quality metric designed for human lung CT scans is presented. The metric can be used for several purposes, including the evaluation of visual quality of CT scans or controlling enhancement processes. The developed method is based on a modified SKFCM image segmentation algorithm combined with the SSIM metric. A lung phantom was constructed for validation purposes. Tests were performed both with synthetic images, using the lung phantom with added noise, and with real CT images. The presented methods include simulations, quantitative studies and subjective evaluation. Experimental results show that the metric values reliably follow the visual image quality of CT.

A Novel Fractional-Order Differentiation Model for Low-Dose CT Image Processing

Low-dose CT (LDCT) images tend to be degraded by excessive mottle noise and steak artifacts. In this paper, we proposed a novel fractional-order differentiation model that can be applied to LDCT image processing as a post-processing technique. The anisotropic diffusion model (proposed by Perona and Malik, i.e., PM model) has good performance in flat regions, total variation (TV) model works better in edge preservation, and fractional-order differentiation models can mitigate block effect while preserving fine details and more structure. The proposed model is based on the weighted combinations of the fractional-order PM model and the fractional-order TV model, which maintains the advantages of PM model, TV model, and fractional-order differentiation models. Moreover, the local intensity variance was added to both weighted coefficient and diffusion coefficient of the proposed model to properly preserve edges and details. A variety of simulated phantom data, including the Shepp–Logan head phantom, the pelvis phantom, and the actual thoracic phantom, were used for experimental validation. The results of numerical simulation and clinical data experiments demonstrate that the proposed approach has a better performance in both noise suppression and detail preservation, when compared with several other existing methods.

Artificial bone with personalised ordering and laser rapid prototyping based on CT image processing

Artificial bone with personalised ordering and laser rapid prototyping based on CT image processing

Internal structure evolution of asphalt mixtures during freeze–thaw cycles

Abstract This paper is an attempt to identify the internal structure evolution within asphalt mixtures under freeze–thaw cycles. Three types of asphalt mixtures were fabricated in the laboratory. X-ray computed tomography technology was employed to capture internal structure within samples before and after the freeze–thaw test. A set of image analysis procedures for extracting the internal structure properties was used to analyze the changes in air void distributions and to evaluate the internal structure evolution under freeze–thaw cycles. Results of X-ray CT image processing illustrated a dramatical degradation in internal structure after the freeze–thaw tests. The change in internal structure mainly occurs in three ways: (1) expansion of existing individual voids, (2) coalescing of two separated air voids, and (3) formation of new voids. Interestingly, the internal structure properties for three types of asphalt mixtures differs from each other and results in various forms of internal structure evolution and micro-crack formation under freeze–thaw cycles. In addition, the differences in internal structure degradation were also evaluated with the levels of water saturation and design void content, indicating their important role in the study of freeze–thaw damage of asphalt mixtures and in the design of asphalt mixtures in cold regions.

Optimized Parallelization for Nonlocal Means Based Low Dose CT Image Processing.

Low dose CT (LDCT) images are often significantly degraded by severely increased mottled noise/artifacts, which can lead to lowered diagnostic accuracy in clinic. The nonlocal means (NLM) filtering can effectively remove mottled noise/artifacts by utilizing large-scale patch similarity information in LDCT images. But the NLM filtering application in LDCT imaging also requires high computation cost because intensive patch similarity calculation within a large searching window is often required to be used to include enough structure-similarity information for noise/artifact suppression. To improve its clinical feasibility, in this study we further optimize the parallelization of NLM filtering by avoiding the repeated computation with the row-wise intensity calculation and the symmetry weight calculation. The shared memory with fast I/O speed is also used in row-wise intensity calculation for the proposed method. Quantitative experiment demonstrates that significant acceleration can be achieved with respect to the traditional straight pixel-wise parallelization.