Magneto-acousto-electrical tomography (MAET) is an imaging method coupled with sound field and magnetic field. The aim of this study is to present some novel experimental results of the mouse liver for the magneto-acousto-electrical tomography measured by two electrodes. The magnetic field in the space of 60 mm3 is about 300 mT which generate by two permanent magnets. A plane transducer with 2.25 MHz center frequency is utilized to generate acoustic waves inside the object. The signal is detected by two similar 1 mm copper foil electrodes. An amplifier is designed to receive the MAET signal, and the gain of the amplifier is adjusted to be 54 dB. The phantom used in this paper is a mouse liver surrounded by a gel phantom with the conductivity of 0.7 S m−1. The gel phantom with the conductivity of 0.7 S m−1 is used to simulate the liver tumor, and the normal mouse liver is filled in the phantom. A series of the MAET signals are detected by the electrodes when the transducer is moved on a pre-set line route, then a B-scan image is realized. The experimental system can provide more information about the tumor and the results show that the MAET is sensitive enough for the potential clinical application of tumor in animal or human.
In the past few years, the limitation of homogeneous electromagnetic metamaterial (EMMM) in magnetic field modulation had been proved by many researches. The introduction of inhomogeneous EMMM (IEMMM) provided a significant progress in improving the range and efficiency of the wireless power transfer system (WPTS). An IEMMM with three kinds of effective permeability came up here. By analysing the effective permeability characteristics of the circular, square, and ‘8’‐shaped coil unit cell and the modulated regulation of magnetic field by negative permeability medium, a two‐dimensional IEMMM with combinations of square and ‘8’‐shaped coil unit cell were studied. The finite element simulation results of WPTS with IEMMM proved an improvement in magnetic field modulation and flux leakage control. In the WPTS, the designed IEMMM is able to improve the power transmission efficiency by up to 28%.
This article presents a series of three-dimensional results for Magneto-acousto-electrical Tomography (MAET), which is a hybrid imaging modality combining the merits of high contrast and high resolution. The ultrasound field and electromagnetic field are coupled to generate current density distribution inside the sample. However, three-dimensional images have not yet been realized for MAET through voltage signals detected by electrodes. In this paper, the mathematical model of MAET is analyzed, and a new image reconstruction scheme is proposed, which is verified by a numerical framework. One three-dimensional numerical model of normal and tumor tissues is formed to analyze the multiphysics problems. In the model, vibration velocity is obtained for pulse type ultrasound excitations with the duration of 0.5 μs. The static magnetic field produced by two permanent magnets is about 300 mT. In order to measure the voltage caused by the MAET effect, two electrodes are attached on the surface of the sample. A series of MAET signals are obtained when the transducer locates in different positions. The distribution of three-dimensional conductivity is recovered by the new image reconstruction scheme. The reconstructed conductivity images are consistent with the original distribution, thus verifying the effectiveness of the new image reconstruction scheme. In addition, the experiment has also validated the mathematical model and simulation results. The simulation and the experimental results indicate that the MAET has the potential to become a new tool to study the electrical properties of tumors in humans.
ObjectiveDistal clavicle fracture classification directly affects the treatment decisions. It is unclear whether the classification systems implemented differ depending on surgeons' backgrounds. This study aimed to compare the interobserver agreement of four classification systems used for lateral clavicle fractures by shoulder specialists and general trauma surgeons.MethodsRadiographs of 20 lateral clavicle fractures representing a full spectrum of adult fracture patterns were analyzed by eight experienced shoulder specialists and eight general trauma surgeons from 10 different hospitals. All cases were graded according to the Orthopedic Trauma Association (OTA), Neer, Jäger/Breitner, and Gongji classification systems. To measure observer agreement, Fleiss' kappa coefficient (κ) was applied and assessed.ResultsWhen only X‐ray films were presented, both groups achieved fair agreement. However, when the 3D‐CT scan images were provided, improved interobserver agreement was found in the specialist group when the OTA, Jäger/Breitner, and Gongji classification systems were used. In the generalist groups, improved agreement was found when using the Gongji classification system. In terms of interobserver reliability, the OTA, Neer, and Jäger/Breitner classification systems showed better agreement among shoulder specialists, while a slightly lower level of agreement was found using the Gongji classification system. For the OTA classification system, interobserver agreement had a mean kappa value of 0.418, ranging from 0.446 (specialist group) to 0.402 (generalist group). For the Neer classification system, interobserver agreement had a mean kappa value of 0.368, ranging from 0.402 (specialist group) to 0.390 (generalist group). For the Jäger/Breitner classification system, the inter‐observer agreement had a mean kappa value of 0.380, ranging from 0.413 (specialist group) to 0.404 (generalist group). For the Gongji classification system, interobserver agreement had a mean kappa value of 0.455, ranging from 0.480 (specialist group) to 0.485 (generalist group).ConclusionGenerally speaking, 3D‐CT scans provide a richer experience that can lead to better results in most classification systems of lateral clavicle fractures, highlighting the value of digitization and specialization in diagnosis and treatment. Competitive interobserver agreement was exhibited in the generalist group using the Gongji classification system, suggesting that the Gongji classification is suitable for general trauma surgeons who are not highly experienced in the shoulder field.
As the electrical properties of biological tissues are highly sensitive to their physiological and pathological status, the noninvasive imaging method of electrical properties also has drawn much attention. Thermo-acoustic tomography with electric excitation (TATE) is a typical noninvasive method of electrical properties for biological tissues. To the best of our knowledge, however, there is no 3D simulation model of TATE. In this paper, a new mathematical model is built, and the 3D TATE equations have been deduced. The performance of TATE has been studied by a series of 3D simulation models, including the tumors with different background tissues, different sizes, and different conductivities. In the simulation results, the Joule heat distribution of tumors has been imaged clearly. In addition, a verification experiment has validated the mathematical model and simulation results. The simulation and experiment results also indicate that the mathematical model can describe TATE well and TATE has the potential to image the tumors with high contrast and high resolution.
Thermo-acoustic imaging with the current injection (TAI-CI) is an emerging medical electrical parameter imaging technology for early detection of human diseases, it combines the advantages of high contrast of electrical impedance imaging and high resolution of ultrasound imaging. The principle of thermoacoustic imaging with the current injection was studied and the experimental system was established. The study results demonstrate that the joule heating is produced inside the objects by injecting current to phantom through a pair of electrodes, and an acoustic signal which involves the electrical parameter information of the objects is excited due to heat expansion. An experimental set for TAI-CI was established to detect and collect the acoustic signals from the semicircular ring gel phantom, the experiments were carried out aiming at low conductivity phantom (1S/m), the electrical parameter variation of the gel phantom was reflected through image reconstruction. The experiments verify the feasibility of the method for low conductivity medium imaging, and provides a basis for potential applications of TAI-CI in biological tissues.
In order to eliminate the limitation caused by the use of a uniform magnetic field mode in magnetically mediated thermoacoustic imaging (MM-TAI), non-uniform magnetic field excitation with a single coil for MM-TAI is proposed in this paper. The theoretical model of the electromagnetic field based on time–space separation and acoustic field problems for MM-TAI is solved. For the inverse problem, the heat absorption distribution is reconstructed by the time reversal technique. The reconstructed results are in good accord with the original structure model, and the image can be clearly identified and agree well with the electric conductivity model. The experimental system is optimized to test the method, then the phantoms with conductivities of 8 S/m and 7 S/m are used for thermoacoustic signal detection and imaging. The signal detecting ability of the low conductivity target has improved significantly. These results provide the basis of MM-TAI for further application in biomedical imaging.
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