Ultrasound imaging of chitosan nerve conduits that bridge sciatic nerve defects in rats

The repair of peripheral nerve injuries with autologous nerve remains the gold standard （Wang et al., 2005; Yao et al., 2010; Deal et al., 2012; Kriebel et al., 2014; Liu et al., 2014; Tamaki et al., 2014; Yu et al., 2014; Zhu and Lou, 2014）. With advances in tissue engineering and biomaterials, tissue-engineered nerve conduits with various biomaterials and structures, such as collagen and chitosan nerve conduits, have already been used in the clinic as alternatives to autologous nerve in the repair of peripheral nerve injury （Wang et al., 2012; Svizenska et al., 2013; Eppenberger et al., 2014; Gu et al., 2014; Koudehi et al., 2014; MoyaDiaz et al., 2014; Novajra et al., 2014; Okamoto et al., 2014; Shea et al., 2014; Singh et al., 2014; Tamaki et al., 2014; Yu et al., 2014）. Therefore, new simple and effective methods

Detection of a glass fiber-reinforced polymer with defects by terahertz computed tomography

Terahertz(THz)computed tomography(THz CT)exhibits the potential to provide a wealth of data,surpassing that of THz tomographic imaging in applications such as detecting embedded defects,particularly defect evolution within a glass fiber-reinforced polymer.To realize high-resolution THz CT,a systematic approach guided by wave propagation simulation was employed.First,the front wave of the THz beam was fine-tuned to realize a beam diameter of<2 mm.To mitigate the strong refractive effect and minimize Fresnel reflection loss,a refractiveindex-matching material was fabricated and utilized as a rounded enclosure for samples with sharp corners.To further improve the reconstruction resolution,a flat surface enclosure was applied to collect all incident beams at the detector.To realize comparable results to those of full-angle CT,a limited-angle CT approach was implemented,and the frequency range 0.1–3 THz was used in the image reconstruction study.The experimental and simulated images were used to validate the findings,and conductive and non-conductive defects measuring 200μm were successfully visualized.Additionally,a custom-built user interface enabled us to visualize the field spatial distribution of the THz beam with respect to frequency.

Defect Recognition in Thermosonic Imaging

This work is aimed at developing an effective method for defect recognition in thermosonic imaging.The heat mechanism of thermosonic imaging is introduced,and the problem for defect recognition is discussed.For this purpose,defect existing in the inner wall of a metal pipeline specimen and defects embedded in a carbon fiber reinforced plastic（CFRP） laminate are tested.The experimental data are processed by pulse phase thermography（PPT） method to show the phase images at different frequencies,and the characteristic of phase angle vs frequency curve of thermal anomalies and sound area is analyzed.A binary image,which is based on the characteristic value of defects,is obtained by a new recognition algorithm to show the defects.Results demonstrate good defect recognition performance for thermosonic imaging,and the reliability of this technique can be improved by the method.

Lamb wave topological imaging for blind hole defects in isotropic plates

The research aims at validating the ability of topological imaging to blind holes in isotropic plates using Lamb waves. Due to the defect is not symmetric around the mid- plane of the plate, the effect of Lamb mode conversion will have to be taken into account. The imaging method is based on two computations of ultrasonic fields, one forward and one adjoint, performed for the defect-free reference medium. The excited signal and scattered Lamb waves caused by the blind hole, are used as emitting sources to compute the forward problem and the adjoint problem, respectively. With the help of the finite element simulations, the natural refocusing process of the multimode Lamb waves at the defect location is visually demonstrated by the transient acoustic field snapshots at the different moments to strengthen the physical mechanism of the topological imaging method. The numerical results demonstrate that topological imaging has relatively stronger applicability to the blind hole in contrast to classical Delay And Sum （DAS） method and Time Reversal （TR） method. The topological imaging could handle complex Lamb wave signals containing mode conversions without the imaging quality being affected. The proposed imaging method presents a certain developing potential for detecting and imaging asymmetric defects in plate-like configurations using Lamb waves.

Congenital aortic arch anomalies: diagnosis using contrast enhanced magnetic resonance angiography

Congenital aortic arch anomalies occur most commonly in children. The disease can be classified into three types： ① obstructive congenital abnormalities, including coarctation of aorta （CoA） and interruption of aortic arch （IAA）; ② nonobstructive congenital abnormalities, including double aortic arch and others; ③ congenital shunt abnormalities, including different types of patent ductus arteriosus （PDA）. Management of patients with congenital aortic arch anomalies relies on imaging. Routine imaging modalities, such as conventional X-ray plain film and transthoracic echocardiography （TTE）, have been recently complemented by magnetic resonance imaging （MRI）.