PURPOSE Magnetic resonance imaging (MRI) of rodents can be expected to be a growing application, particularly when translatory imaging research "from mouse to man" is envisioned. 7 T high-field human whole-body MR systems provide a powerful platform for high-resolution small animal imaging. For achieving adequate spatial resolution, dedicated radiofrequency coils have to be designed to provide ...

B. Xu, B. K. Li, S. Crozier, F. Liu, Q. Wei School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia INTRODUCTION: High magnetic field (frequency) MRI technology has brought considerable engineering challenges in the form of ancillary hardware, including RF resonators. Studies in high frequency MRI have shown significant interact...

Parallel excitation [1,2] with a multi-element Radio Frequency (RF) transceiver array [3-9] as a contemporary methodology has been advocated for human MR imaging at ultrahigh magnetic fields (7 Tesla and above). In ultrahigh field MRI, the required high operating frequency and thus shortened wavelength of radio frequency waves creates a complex wave behavior and increased phase variation of RF ...

PURPOSE Parallel transmission (PTx) offers spatial control of radiofrequency (RF) fields that can be used to mitigate nonuniformity effects in high-field MRI. In practice, the ability to achieve uniform RF fields by static shimming is limited by the typically small number of channels. Thus, tailored RF pulses that mix gradient with RF encoding have been proposed. A complementary approach termed...

PURPOSE To improve ultrahigh field diffusion-weighted imaging (DWI) in the presence of inhomogeneous transmit B1 field by designing a novel semi-adiabatic single-refocused DWI technique. METHODS A 180° slice-selective, adiabatic radiofrequency (RF) pulse of 4 ms duration was designed using the adiabatic Shinnar-Le Roux algorithm. A matched-phase slice-selective 90° RF pulse of 8 ms duration w...

The de facto standard cost function has been used heretofore to characterize the performance of pulses designed using optimal control theory. The freedom to choose new, creative quality factors designed for specific purposes is demonstrated. While the methodology has more general applicability, its utility is illustrated by comparison to a consistently chosen example--broadband excitation. The ...

We have constructed a small-bore insertable gradient coil with two linear gradient imaging regions and interfaced it with an MRI scanner. We have also constructed an RF system capable of transmitting or receiving in both regions simultaneously.Designs for conductor placement for two-region X-, Y- and Z-gradient coils were optimized by simulated annealing. Wire patterns for each axis were chosen...

Introduction: The increased longitudinal relaxation time of the blood at ultrahigh field (UHF) can improve non-contrast enhanced perfusion imaging using arterial spin labeling (ASL), especially for targeted tissues with long arterial transit times and/or intrinsic low perfusion, such as the prostate. One well-known challenge for UHF imaging is the destructive interference of RF pulses (1), whic...

It is well known that good quality spectra are dependent on the magnetic field homogeneity of the magnet. The field homogeneity, in turn, is dependant on the magnetic field strength, the bore design etc. In the case of the MAGNETOM Verio, a 3T wide and shorter bore scanner, these factors are of concern for the spectroscopy community. The Verio uses an innovative technology known as “TrueForm”. ...