All-metal Inserts Research Articles

Metal artifact reduction techniques for single energy CT and dual-energy CT with various metal materials.

Objective:The aim of the current study is to evaluate the effectiveness of reduction metal artifacts using kV-CT image with the single-energy based metal artefact reduction (SEMAR) technique by single-energy reconstruction, monochromatic CT and rED reconstructed by dual-energy reconstruction.Methods:Seven different metal materials (brass, aluminum, copper, stainless, steel, lead and titanium) were placed inside the water-based PMMA phantom. After DECT-based scan, the artefact index (AI) were evaluated with the kV-CT images with and without SEMAR by single-energy reconstruction, and raw-data based electron density (rED), monochromatic CT images by dual-energy reconstruction. Moreover, the AI with evaluated with rED and the converted ED images from the kV-CT and monochromatic CT images.Results:The minimum average value of the AI with all-metal inserts was approximately 80 keV. The AI without SEMAR was larger than that with SEMAR for the 80 kV and 135 kV CT images. In the comparison of the AI for the rED and ED images that were converted from 80 kV and 135 kV CT images with and without SEMAR, the monochromatic CT images of the PMMA phantom with inserted metal materials at 80 keV revealed that the kV-CT with SEMAR reduced the metal artefact substantially.Conclusion:The converted ED from the kV-CT and monochromatic CT images could be useful for a comparison of the AI using the same contrast scale. The kV-CT image with SEMAR by single-energy reconstruction was found to substantially reduce metal artefact.Advances in knowledge:The effectiveness of reduction of metal artifacts using single-energy based metal artefact reduction (SEMAR) technique and dual-energy CT (DECT) was evaluated the electron density conversion techniques.

Design of waveguide E-plane filters with all-metal inserts by equal ripple optimization

An optimization based approach to the design of E-plane filters is described. An optimization procedure based on Cohn's equal ripple optimization is developed. This vector procedure has several advantages over the general purpose optimization routines previously applied to the design of F-plane filters. The problem of local minima does not arise. Optimization is carried out with respect to the Chebyshev (or minimax) criteria. Less frequency sampling and therefore less calculation of the electrical parameters of E-plane discontinuities is required. The design of a symmetrical F-plane filter is considered. Higher order mode interaction between E-plane discontinuities is not included in the design. For the design example considered this is shown not to be significant. A numerically efficient method, requiring only real scalar arithmetic, for calculating the insertion loss of a symmetrical cascade of lossless symmetrical 2-ports is employed. Measurements on a fabricated filter confirm the accuracy of the design procedure. >

A simplified CAD of millimeter-wave diplexer with E-plane T-junction and all-metal insert filters

An equivalent circuit theory design of a class of rectangular waveguide E-plane T-junction diplexer with E-plane all-metal insert filters is presented. Element values of equivalent circuit models of E-plane T-junction proposed in [1] are computed and approximated. The parameters of the filters designed by [2] are also given. By use of the network combining technique, the scattering matrix of the diplexer is obtained and optimized according to the diplexer specification with a novel objective function. The experimental results show a fairly good agreement with the computed results.

A rigorous cad of millimeter wave bandpass filter with all-metal insert in waveguide

In this paper, a bandpass filter with all-metal insert, an inductive strip in the E-plane of a waveguide is analyzed by a prototype filter and the scattering matrix of the strip is calculated by electromagnetic fields theory theoretically. By means of matrix combining technique, the scattering matrix of a bandpass filter of this type is obtained. And a rigourous error function is used to optimize the CAD program by Powell's method and make the experimental results agree well with the theory design at V-band.

MetallicE-plane filter with cavities of different cutoff frequency

A planar integrated circuit filter with multiple all-metal inserts and multiple abrupt waveguide step-wall discontinuities is introduced which achieves broadband high attenuation in the second stopband. The design is based on field expansion into suitably normalised eigenmodes which yield directly the modal S-matrix. This theory allows the immediate inclusion of both the higher-order mode interaction at all discontinuities and the finite thickness of the inserts. Computer-optimised design data for a five-resonator Ka-band prototype filter at 27 GHz midband frequency provide a minimum stopband attenuation of 50 dB between 27.5 and 44.5 GHz.

Design and development of a superconducting magnet system for study of magnetoresistance in the temperature range 1.5–300 K

The design and fabrication of an all-metal cryostat, superconducting magnet and variable temperature sample holder insert for the measurement of magnetoresistance at temperatures in the range 1.5–300 K are described. A field of 50 kilogauss has been achieved at the centre of a one-inch bore superconducting solenoid and has a uniformity of 0.2% over an axial distance of 20 mm around the centre of the solenoid. Also, the design and construction of vapour cooled current leads for the magnet are discussed.

Design of Waveguide E-Plane Filters with All-Metal Inserts

Waveguide E-plane filters with all-metal inserts are designed by a procedure based on the reflection coefficients of axial inductive strips. The scattering matrix, representing the junction in a bifurcated waveguide, is calculated by a mode-matching method. The reflection coefficient for an inductive strip is then obtained by cascading two scattering matrices separated by a distance equal to the stripwidth. The design is valid up to moderate bandwidths, except for the narrowband design at the higher waveguide frequency range, where both the center frequency and the bandwidth are inaccurate. Possible sources of error are studied and a method minimizing the error is proposed.