Fan Yubo

An automatic method of synthesizing panoramic radiograph by unwrapping dental CT image

Panoramic radiographs synthesized from dental CT images manifest high quality than conventional dental panoramic radiograph and have been used in clinical treatment, but some manual operations are needed in current synthesizing algorithms. This paper presents a new algorithm to synthesize panoramic radiographs from dental CT images automatically. Firstly, projection image of the horizontal CT image is generated by maximum intensity projection (MIP). Then, a modified Ostus threshold method is used to segment dental arch area in the projection images. After that, a reference curve is obtained by fitting the medial axis of dental arch area. Finally, the CT slices are unwrapped normal to the reference curve and the panoramic radiograph is generated by synthesizing the projection of unwrapped images in frontal axis. This algorithm is fully automatic and the panoramic radiograph synthesized from dental CT images with this algorithm shows less geometric distortion and blurring.

In vitro and in vivo studies on as-extruded Mg-5.25wt.%Zn-0.6wt.%Ca alloy as biodegradable metal

Magnesium alloys have shown prospective applications as a new biodegradable metal within bone. To garantee the longterm biocompatibility, a Mg-Zn-Ca alloy, composing of essential elements for human, was prepared and its feasibility for orthopedic applications was investigated. The in vitro and in vivo corrosion of Mg-Zn-Ca alloy as well as the biocompatibility were studied. The in vitro corrosion tests in five kinds of physiological solutions showed that the corrosion rates and corrosion morphologies of the alloy were strongly influenced by the solution used. The addition of serum in Hank’s and MEM significantly slowed down the corrosion rate and improved the corrosion uniformity of the alloy. The corrosion rate decreased with increasing serum concentration. The alloy showed the slowest corrosion rate as well as homogeneous corrosion morphology in MEM+10%FBS. Both the indirect and direct cell experiments indicated good cytocompatibility of the extruded Mg-Zn-Ca alloy. In vivo, we observed a gradual degradation process from the surface of extruded Mg-Zn-Ca alloy and only 40% in volume of implant was left after 4 weeks implantation in medullary cavities of mice. The micro-CT and histological analyses revealed its good biocompatibility with peri-implant new bone formation and increasing cortical bone thickness with increasing implantation period. This study showed that the extruded Mg-Zn-Ca alloy provided sufficient biocompatibility for orthopedic application, though the in vivo corrosion rate should be further reduced for clinical use.摘要可降解医用镁合金在骨科领域显示出良好的应用前景. 为了保证镁合金的生物相容性, 本文设计了全营养元素组成的Mg-Zn-Ca合金, 研究了其体内外腐蚀及生物相容性. Mg-Zn-Ca合金在五种模拟体液中的腐蚀测试结果表明在Hank’s和MEM中添加血清能够降低合金腐蚀速度, 并提高腐蚀均匀性. 血清浓度越高, 合金腐蚀速率越低. Mg-Zn-Ca合金在MEM+10%FBS溶液中腐蚀速率低, 腐蚀形貌均匀. 直接法和间接法的细胞实验结果均显示Mg-Zn-Ca合金具有良好的细胞相容性. 动物实验结果表明, Mg-Zn-Ca合金在小鼠骨髓腔内逐步降解, 4周后残余40 vol.%. micro-CT和组织学观察显示植入体周围有新骨形成, 且随着植入时间延长, 皮质骨厚度增加. 因此, 挤压态Mg-Zn-Ca合金具有良好的生物相容性, 有望用作骨科植入材料, 但是其体内降解速率还应进一步降低.

NUMERICAL ANALYSIS OF THE IMPACT OF ATHEROSCLEROTIC PLAQUE AND DIFFERENT STENT SPACING ON DRUG DEPOSITION

Objectives: To investigate the influence of atherosclerotic plaque and different drug-eluting stent (DES) spacing on drug deposition in the curved artery wall. Methods: Based on the computational fluid dynamics (CFD) method, the numerical investigation on distributions of drug concentration in the artery wall was carried out considering three different interstrut distances and five values of the plaque diffusion coefficients. The results were compared with those of the model without plaque. Results: Under the same stent spacing, drug deposition weakly increased with the increasing plaque diffusion coefficient. When the same diffusion coefficient value was taken, drug deposition presented steady growth with the expansion of stent spacing. When the stent spacing was of 1-strut length or the diffusion coefficient of plaque was much smaller than the diffusion coefficient of tissue (an order of magnitude or more), the drug deposition would be evidently reduced. Conclusions: In a curved artery, the stent spacing is still an important factor in drug deposition. The diffusion coefficients of plaque have little influence on the average drug concentration, but they show a relatively obvious effect on drug distributions.

The Observation of the PG-depletion in Progressive Trypsin Digested Articular Cartilage Based on Conventional A-mode Ultrasound

This study tried to monitor proteoglycans (PG)-depletion in progressive trypsin digested porcine articular cartilage (AC) samples with a conventional ultrasound system. 10 cartilage-bone samples were prepared from normal porcine femoral condyle cartilages and were digested with 0.25% trypsin solution for two hours. The dynamic process of the PG digestion was explored using an A-mode ultrasound experiment system with 10MHz center frequency. The speed of PG-depletion and the degree of PG-depletion were estimated from ultrasound echo signal. The results showed that 10MHz ultrasound is valuable in tracking the degree of PG-digestion. The transient speed of PG-digestion decreased with digesting time and tissue depth. The digestion speed is faster in the superficial layer of the cartilage samples (0.93 ± 0.3M/min) than that in deeper layers (0.26 ± 0.12 M/min at 50% of the full thickness). The histological image also confirmed the validity of the ultrasound observation.. This study may provide some useful information in identifying cartilage matrix integrity and osteoarthritis (OA) disease progression.

The Correlation Study of Ultrasonic Parameters and Young’s Modulus of Cancellous Bone during Decalcification

This study applied a chemical decalcification method to explore the variations of ultrasonic parameters and Young’s modulus of the cancellous bone samples at different decalcification stages and the correlations between them. Cancellous bone specimens were obtained from proximal ends of bovine femoral and then resorted to progressively decalcification with ethylene diamine tetraacetic acid solution. Ultrasonic parameters and young’s modulus were measured and computed based on ultrasonic experiment and mechanical measurement respectively at different decalcification stages, and their correlations were investigated using SPSS software. The results showed that all the parameters including speed of sound, broadband ultrasonic attenuation, amplitude attenuation and Young’s modulus decreased with calcium loss. Strong linear correlations between Young’s modulus and ultrasonic parameters (correlation coefficient r(E, SOS)=0.913, r(E, nBUA)=0.988 and r(E, AA)=0.964) were found. This study may provide some useful information for the detection of osteoporosis with the methods of ultrasonic.

The observation of hip joint cartilage of elderly people based on EPIC Micro-CT

The objective of this study was to observe the age-related changes of sulfated glycosaminoglycan (sGAG) content and surface roughness of hip joint cartilage of elderly people based on Equilibrium Partitioning of an Ionic Contrast Agent (EPIC) Micro-CT. 35 human hip cartilage-bone samples were prepared from hip-fracture patients whose age were from 50 to 100 years old and divided into 5 groups (10 years as an age group). They were first immersed in 20% concentration of the contrast agent Meglumine Diatrizoate (MD) for 6 hours at 37°C, and scanned by Micro-CT after taken out from the contrast agent. The X-ray mean attenuation and hip joint cartilage surface roughness were calculated. The results showed the X-ray mean attenuation of the entire hip joint cartilage increased about 17.44% from the 50 age group to the 80 age group (from 1294.61±97.77HU to 1520.39±184.56HU), but it decreased about 6.43% in the 90 age group compared to the 80 age group (from 1520.39±184.56HU to 1422.55±106.37HU). Moreover, the X-ray mean attenuations of the superficial layer, middle layer and radical layer of cartilage declined successively in the different age groups. Regarding of the superficial layer and middle layer from the 50 age group to the 80 age group, they rose about 31.21 % and 43.02% respectively (from 1472.40±138.96HU to 1931.99±199.69HU and 1271.83±58.36HU to 1819.07±213.55HU), and also reduced 4.64% and 6.03% separately in the 90 age group (from 1931.99±199.69HU to 1798.12±153.32HU, and 1819.07±213.55HU to 1653.22±169.46HU), while the radical layer showed no significant change along with age increase. The hip joint cartilage surface roughness changes only 5.31% with age increase (from 13.64±5.17μm to 14.36±5.21μm).

Assessment of glycosaminoglycan in progressive trypsin digested cartilage based on contrast-agent enhanced Micro-CT

The early degeneration of articular cartilage (AC) is closely related to the change in glycosaminoglycan (GAG) content. The observation of GAG is therefore an appropriate way for evaluating the degree of AC degeneration and diagnosing osteoarthritis. In this study, the method of contrast-agent enhanced Micro-CT, which has been demonstrated as a potential method for quantitatively analyzing the GAG content, was applied in trypsin digested AC. 102 specimens from fresh bovine femoral condyles were used in this study. 12 specimens were used for exploring the adaptive contrast-agent concentration, incubation time and Micro-CT imaging method. And other 90 were used for GAG degradation experiment. Incubation for 6h with the concentration of 20% contrast-agent Meglumine Diatrizoate (MD) at 37°C was selected as the experiment protocol. Based on this protocol, the relationship between degradation time and the average X-ray attenuation of the samples was obtained, which had a rising tendency within the 50 min degradation (from 1563HU to 1923HU, increased about 23.03%). The average degradation depth of the samples increased with the degradation time (from 0mm (no degradation) to 0.6mm (50 min degradation)). Moreover, the change in the average X-ray attenuation of the samples was linearly and inversely related to their GAG content (r = -0.771, p<; 0.01). To conclude, contrast-agent enhanced Micro-CT can provide useful information about trypsin-induced progressive GAG depletion in AC and can reflect variations of GAG content via X-ray attenuation. The results of this study m provide a basis for quantitatively evaluating the cartilage degradation, and also offer a reference to the early diagnosis of osteoarthritis.

An ERP research on the cerebral functional regions correlated to stereoscopic perception

The binocular disparity is the prime of forming stereopsis. The researches were not focused on basic visual functional areas affecting stereoscopic perception induced by binocular disparity. In this paper, ERP technology was used to study the regulatory region in cerebral cortex which relates to stereoscopic perception induced by binocular disparity. We chose eight subjects to conduct the experiment by using images with different binocular disparities, and we found the stereoscopic perception resulted from binocular disparity evoked N2 wave on all of occipital lobe with large amplitude at 180ms. In addition, the amplitudes of N2 waves in the O channels were lower than those of other channels. It means the regulation of stereoscopic perception induced by binocular disparity needs basic and advanced visual functional areas work together. Meanwhile, it also means the principle areas are the advanced visual functional areas.

The Finite Element Study of the Subsequent Injury in a MCL Deficient Knee

The medial collateral ligament (MCL) tears frequently in sports and is commonly accompanied by ACL and medial meniscus injuries. Experimental and clinical studies have been widely carried out, but were limited to obtaining stress distribution and conducting parametric studies. The purposes of this study were to develop a validated three dimensional finite element model of knee joint, and to analyze the subsequent changes of the kinematics and stress distribution of corresponding structures induced by different levels of MCL rupture. The model was developed from magnetic resonance images and validated by published experimental data. A loading and boundary condition of passive knee flexion (0 60 degrees) were applied to the knee with an intact MCL, superficial MCL torn, deep MCL torn and complete MCL torn. The most significant differences found were the deformation within medial meniscus as well as the valgus degree of the knee between pre- and post-injury MCL condition. The computational results indicated that the deep MCL prevents excessive translation of medial meniscus, while the superficial MCL provides most of the restraining valgus moment. This study could help to understand the various subsequent injuries led by MCL injuries, and to predict the risk positions in the joint. Furthermore, this model could shed some light on the mechanism of MCL injuries and the treatments.

Three-Dimensional Reconstruction and Analysis of Human Central Sulcus Based on Visualization Toolkit

Quantitative shape analysis of human central sulcus (CS) is important to understand the structure-function relationship. However, shape analysis of CS is a tedious process, and there is no analysis software that can be used directly for 3D reconstruction and morphological analysis of CS. In this paper, we developed the software with the VTK technology for three-dimensional (3D) reconstruction and shape analysis of CS. The functions of this software included: constructing and displaying the 3D model of CS with VTK unstructured grid mesh; achieving detailed morphological information by interaction operation of cutting and picking; analyzing global and local morphological characteristics such as surface area, average curvature, degree of concave and so on; visualizing the calculated results using pseudocolor. With the developed software, 12 cases of CS were reconstructed, and the global and local features that describe CS were analyzed. The software developed in this paper will provide researchers more accurate information on morphology of CS, and will help them describe the structure-function relationships of CS more precisely and effectively.