Computer‑aided CT image processing and modeling method for tibia microstructure

We present a method for computed tomography(CT)image processing and modeling for tibia microstructure,achieved by using computer graphics and fractal theory.Given the large-scale image data of tibia species with DICOM standard for clinical applications,we take advantage of algorithms such as image binarization,hot pixel removing and close operation to obtain visually clear image for tibia microstructure.All of these images are based on 20 CT scanning images with 30μm slice thickness and 30μm interval and continuous changes in pores.For each pore,we determine its profile by using an improved algorithm for edge detection.Then,to calculate its three-dimensional fractal dimension,we measure the circumference perimeter and area of the pores of bone microstructure using a line fitting method based on the least squares.Subsequently,we put forward an algorithm for the pore profiles through ellipse fitting.The results show that the pores have significant fractal characteristics because of the good linear correlation between the perimeter and the area parameters in log–log scale coordinates system,and the ratio of the elliptical short axis to the long axis through ellipse fitting tends to 0.6501.Based on support vector machine and structural risk minimization principle,we put forward a mapping database theory of structure parameters among the pores of CT images and fractal dimension,Poisson’s ratios,porosity and equivalent aperture.On this basis,we put forward a new concept for 3D modeling called precision-measuring digital expressing to reconstruct tibia microstructure for human hard tissue.

Status and prospects of frozen soil studies using CT technology

This paper introduces the characteristics of Computed Tomography （CT） technology and reviews its history, current situation, representative achievements, and use of using CT technology on frozen soil study, including auxiliary equipment specially de- signed for frozen soil studies. CT numbers are used to analyze frozen soil internal structure change, defining and exploring dam- age evolution, and use of CT images on observing soil mesostructure. Finally, this paper presents existing problems confronted by using CT in frozen soil studies, possible solutions and challenges, among which, we introduce high quality CT image processing for frozen soils, and relations between CT number change and each component change on frozen soil samples within the region of interest. It is shown that present CT technology is one of the most ideal and effective technology to study frozen soil mesostructure using non-desmactive testing. CT technology will play a key role in the study and development in the field of frozen soil by means of auxiliary equipment and the digital imaging processing.

Microstructural Characteristics of Asphalt Concrete with Different Gradations by X-ray CT

The main objective of this paper is to evaluate the effects of asphalt concrete types on the microstructural characteristics at high-temperature. Suspend-dense structure and Skeleton-dense structure were selected to investigate the deformation of pavement at meso-scale. The internal microstructures of typical asphalt concretes, AC, SUP and SMA, were scanned by X-ray CT device, and microstructural changes before and after high-temperature damage were researched by digital image processing. Adaptive threshold segmentation algorithm（ATSA） based on image radius was developed and utilized to obtain the binary images of aggregates, air-voids and asphalt mastic. Then the shape and distribution of air-voids and aggregates were analyzed. The results show that the ATSA can distinguish the target and background effectively. Gradation and coarse aggregate size of asphalt mixtures have an obvious influence on the distribution of air-voids. The movements of aggregate particles are complex and aggregates with elliptic sharp show great rotation. The effect of gradation on microstructure during high-temperature damage promotes the research about the failure mechanism of asphalt concrete pavement.