Wenhui Yang

Conductivity Image Reconstruction of Oblique Slice With C-Shaped Open Permanent Magnet MRI Systems

This work provides an improved image reconstruction technique, oblique slice magnetic resonance electrical impedance tomography (OS-MREIT), which can provide any cross-sectional conductivity distribution images with any type of MRI scanner. The OS-MREIT method can obtain conductivity distribution images using one component of magnetic field induced by injected currents with rotating subject once, and in the two-dimensional case, the conductivity distribution image can be reconstructed without rotating subject. The results of OS-MREIT studies performed with homemade C-shaped open permanent magnet MRI scanner are also presented in this work.

Bacterial Magnetic Nanoparticles as Peroxidase Mimetics and Application in Immunoassay

Although progress in nanosynthesis has succeeded in making nanoscale particles from iron oxide, the research about natural magnetic nanoparticles, magnetosomes, is still a current interest because of their intrinsic magnetic features, nano‐features, membrane‐enclosed features and genetic control of size and morphology properties. In this study, we investigated magnetosomes’ intrinsic peroxidase‐like activity similar to that found in artificial magnetic nanoparticles. We characterized the catalytic activity by varying the method of extraction and storage, the pH value, the temperature and the H2O2 concentration. Based on these finding, we developed a simplified immunoassay approach to use magnetosomes as a peroxidase mimic catalyst and a magnetic separator as well.

Field free line generation for Magnetic Particle Imaging based on the Mirror Rule

A novel approach for the generation of the Field Free Line (FFL) with four circular coils is proposed in this paper. A rule for the generation of FFL with four circular coils called Mirror Rule is established and proved based on Biot-Savart Law. Calculations of the FFL field distribution were performed. The relationships between the coil rotation angle and the field inhomogeneity as well as field efficiency were studied. The Mirror Rule for FFL generation and the calculation results were also testified by FEM simulation using the Maxwell software. Based on the Mirror Rule, MPI using a dual-surface FFL generator is able to avoid the patient rotation and promising for future clinical usage.

A simulation study for a novel generation method of electro-drive rotating Field free line

As a novel tomography methodology, Magnetic Particle Imaging (MPI) has been obtained more and more attentions. It has been proven in theory that the Field-free line based MPI has about 10 times of sensitivity than the Field-free point based MPI [1]. Then, the generation and rotation of FFL has become the crucial problem for the realization of Projection-Reconstruction Algorithm based MPI. So far, there are mainly two approaches to generate and rotate a FFL. One way is electro-drive [2], the other is mechanically. The electric way is obviously more flexible and fast than the mechanical way. According to the mirror image rule [3], a novel coil design was proposed in this paper to generate a rotating FFL electronically, and a simulation study was performed to testify its feasibility.

The Development of HITFiL Cyclotron Magnet

A recently constructed cyclotron magnet at the Institute of Modern Physics of Chinese Academy of Sciences (IMPCAS) will be used as the injector of Heavy Ion Therapy Facility in Lanzhou (HITFiL). The diameter of the magnet is 2.92 m and its height is 1.52 m. The total weight of the magnet is 70 tons. The isochronous magnetic field for q/m = 5/12 is achieved by appropriate pole edge profile. The paper discusses the various design and fabrication aspects of the magnet. The paper also presents the field measurement results and its comparison with simulation.

The Study of Synchrotron Quadrupole in HIMM

A new project named Heavy Ion Medical Machine is currently being built at the Institute of Modern Physics, Chinese Academy of Sciences. Its synchrotron includes 8 dipoles, 12 quadrupoles, 9 sextupoles, and other magnets. For the synchrotron quadrupole, we use the software OPERA to simulate the magnetic field homogeneity and high-order harmonics, and a series of error analysis show some manufacture and assemble errors could affect the magnetic field. In addition, compact synchrotron design can lead to the smaller distance among magnets; thus, the influence on magnetic field between quadrupole and sextupole would be also discussed. Finally, some magnetic field measurement results of quadrupole prototype will be also introduced.

Design and implementation of MRI RF coil based on 3D printing

3D printing is the latest developed rapid prototyping technology. It has been applied in the field of industrial design, architecture, automotive, aerospace, medical industries, etc. In this paper, 3D printing technology was used to made magnetic resonance imaging RF coils. The results shown that RF coil designed using 3D printing technology has the following advantages: firstly, the printing material PLA has good insulation properties and low RF loss. The coil made with PLA has high Q value. Secondly, the printing material PLA has no impact on the signals of imaged sample. Thirdly, material has good mechanical properties and the coil can be produced through rational design to made variety of structures to meet the needs of research and clinical applications. Low production cost for coils, especially for some of the complex shape of the coil, has a special advantage.

A new method of decoupling for gradient systems in MRI

A set of external coils is designed to eliminate the induced voltage in shim coils caused by the changing current in the gradient coils. By placing the external coil near the line which supplies the current for the gradient coil in a certain way and inserting it into the circuit of shim coils, a induced voltage which has the same wave form with the induced voltage in the shim coil is generated and consequently the coupling between the shim coil and the gradient coil is eliminated. Moreover, the induced voltages of various shim coils are simulated and the parameter of one external coil is determined by the result of the simulation.

A Comparison of Several Phase Unwrapping Methods in MREIT

Phase unwrapping problem in magnetic resonance electrical impedance tomography is discussed in this paper. We use the modified model-based phase unwrapping method to unwrap the wrapped phase images and its performance is evaluated through the experimental results. Several phase unwrapping methods are compared.

A Novel Conductivity Reconstruction Algorithm for Magnetic Resonance Electrical Impedance Tomography (MREIT)

In this paper a novel conductivity reconstruction algorithm for MREIT was proposed. The algorithm can be implemented utilizing permanent magnetic resonance imaging system (Generally the main magnetic field is perpendicular to the horizontal plane.). We distribute the electrodes on the boundary of the selected slice which is not perpendicular to the main magnetic field. The magnetic flux density induced by the applied currents in the selected slice has a component in the direction of the main magnetic field and the component can be measured. Then the equation expressing the relation between the conductivity and the measured magnetic flux density was obtained. In order to guarantee the uniqueness of the reconstructed conductivity, two different solutions were given. The corresponding algorithm was proposed and analyzed. The performance of the algorithm was also discussed.