Single Cable Transmission for Multi-Channel MRI using Frequency Division Multiplexing

Parallel imaging and RF array coils require a great quantity of MRI channels, which can produce ghosting and interference to decrease imaging SNR. In this work, we make use of a frequency division multiplexing (FDM) technique to combine several channel signals and transmit them in single cable. At present the PCB board is prototyped and tested with the signal generator. We propose to build the completed circuit with coil array on board to recover the multichannel FID signals.published_or_final_versio

Array with multiple loops for vertical field system

For vertical field MRI applications, the structure of the loop array is quite different from those in a horizontal-magnetic-field system. The conventional decoupling techniques are hard to be extended to vertical MRI system. Therefore, the loops for vertical MRI system are quite difficult to decouple. So far the coil array with up to two loop coils have been investigated on open low-field MRI, the array with more than three loop coils is sparsely reported. In this study, we present a decoupling technique using inductors for vertical-field loop coils. A four-channel array consisted of 3 loops and a saddle coil has been built for human knee at 0.5T vertical MRI system.published_or_final_versio

Comparison of RF Penetration and G-factor of Different Coil Arrays for Parallel Imaging

Geometry factor and RF penetration of different kinds of coil arrays for parallel imaging were evaluated by simulations using MATLAB and XFDTD software. The results show that the coil arrays with loop structure are superior to the planar strip arrays in terms of g-map and RF penetration. The overlapped loop array has better RF penetration, while the non-overlapped one has a lower noise level in parallel imaging.published_or_final_versio

Comparison of Optical Modulation Methods for RF Coil Interlinks

Optical modulation method is one of the key factors in the optical link design for MRI RF coil interlinks. In this work, link performances of direct modulation by laser diode and external modulation by Mach Zehnder Interferometer are compared in the aspects of power gain, modulation bandwidth, noise figure and dynamic range. An external optical link can achieve better performance by the use of a low noise and high power laser. However, a direct optical link shows advantages in link structure, compact size and low cost. It is more feasible in engineering for large coil array interlinks.published_or_final_versio

Microstrip Loop Array (MLA) for Parallel Imaging

The microstrip loop array (MLA), an improved version of planar strip array, is proposed which take advantage of loop geometry. Without much loss of the well-decoupling benefit of strip line arrays, the proposed microstrip loop arrays have well-localized sensitivity profiles which are more suitable for parallel imaging. Simulation and experiment results show that microstrip loop coils have sensitivity profiles like conventional loop coils, while the mutual coupling is 10-20dB less at same distances. A sensitivity-encoded cardiac imaging was performed to demonstrate the suitability of MLA for parallel imaging.published_or_final_versio

Noise Figure and Dynamic Range Optimization in Optical Links for MRI Applications

MRI applications impose critical requirements in noise figure and dynamic range for optical links used for coil interconnect. To reduce the intrinsic high noise figure of optical links, a low-noise preamp must be used. But it also brings the side effect of dynamic range reduction. Compromise must be made between noise figure and dynamic range to optimize the optical link to meet the critical requirement in MRI. Dynamic range of the current optical link is still a challenge for high field imaging above 3T and needs to be further improved.published_or_final_versio

Digital wireless Transmission for MRI

Analog wireless transmission has been reported for MRI application recently to reduce the interference among the array cables. In this work, we have designed and implemented a new transmission system based on digital wireless technique of WLAN IEEE 802.11b. Frequency Division Multiplexing (FDM) method also is proposed to expand possible more array channels for future MR applications.published_or_final_versio

A Direct Modulated Optical Link for MR Coil Array Interconnect

A direct modulated optical link for MR coil array interconnect has been developed. The link uses a diode laser to modulate RF signals directly, and needs only one fiber for each channel. It has a power gain of ¨C18dB, noise figure of 29dB and dynamic range of 110dBHz. The noise figure can be reduced to below 1dB by a low noise preamp. Compared with an external modulated optical link, a direct modulated link has simpler link structure, lower cost and more compact size, so it is more advantageous for large coil array interconnect.published_or_final_versio

Optimal Driving Configuration and Coil Array Geometry for Parallel Imaging

In order to address concerns about optimal driving configuration and coil array geometry for parallel imaging, SNR and g-factor are evaluated at 200MHz for different coil array configurations. Electromagnetic simulation results show that the regularly accordant ports position and three dimensional layouts of coil elements will gain much higher SNR and better parallel imaging performance.published_or_final_versio

Use of Bi-2223 HTS tapes as RF coils 1.5T MRI

High temperature superconducting (HTS) tapes are potential materials for RF coils in MRI due to their advantages of much lower cost and easier fabrication over HTS films. Resistance of HTS tape coils in the magnetic field was evaluated. A HTS tape coil with 50mm in diameter was designed and built for 1.5T high field MRI. This HTS tape coil demonstrated a 1.11-fold and a 1.36-fold SNR improvement over the same size copper coil at 77K and 300K respectively.published_or_final_versio