Introduction: Parallel transmission has proven to provide good results for spatially selective excitation with reasonable RF-pulse durations [1]. For best spatial definition, exact matching of RF-pulses with a simultaneously played out gradient waveform, which defines a k-space position for every point in time, is crucial. However off-resonance effects and gradient imperfections may lead to dis...

A non-scaling fixed field alternating gradient (nsFFAG) accelerator is being designed for helium ion therapy. This facility will consist of 2 nested rings, treating with helium ions (He) and image with hydrogen ions (H + 2 ). Compared to protons, ions deliver a more conformal dose with a significant reduction in range straggling and beam broadening. Carbon ions are currently used and there are ...

Muon cooling schemes typically involve placing RF cavities in intense magnetic fields. Ongoing work has shown that this may reduce the maximum RF gradient by a significant factor. A linear cooling channel scheme is presented whereby RF cavities sit in much smaller fields. In addition, a scheme is studied for recirculating muons through this linear cooling channel in order to re-use hardware.

Purpose: Patients with many types of common implants, including pacemakers and neurostimulators, are ineligible for MR scans due to the potential for tissue heating arising from RF coupling between the excitation field and their device. The severity of this coupling can be detected by reversing the RF polarization in the birdcage RF receiver. Ideally, this results in MR signal only around coupl...

An MRI sequence is an ordered combination of RF and gradient pulses designed to acquire the data to form the image. In this chapter I will describe the basic gradient echo, spin echo and inversion recovery sequences used in MRI. The data to create an MR image is obtained in a series of steps. First the tissue magnetisation is excited using an RF pulse in the presence of a slice select gradient....

An important aim of nondestructive evaluation is to quantify flaws in components using sensor measurements. In pursuit of this aim, a method has been developed for finding the size and shape of planar cracks in electrical conductors from single-frequency eddy-current probe impedance measurements. In the direct problem, the change in the impedance of an eddycurrent probe due to a crack in a cond...

The accommodation microfluctuations are thought to be used by the accommodation controller to obtain information about the direction and magnitude of the required response by monitoring changes in the contrast gradient of this image. The contrast gradient can be altered by presenting different spatial frequency (SF) targets to the eye. Twelve myopes (MYOs) and 12 emmetropes (EMMs) viewed sine a...

Abstract In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentration gradient is modelled through Fick’s law, and a new constitutive relation for the mass flu...

We experimentally investigate the properties of radio-frequency-dressed potentials for Bose-Einstein condensates on atom chips. The three-dimensional potential forms a connected pair of parallel waveguides. We show that rf-dressed potentials are robust against the effect of small magnetic-field variations on the trap potential. Long-lived dipole oscillations of condensates induced in the rf-dre...

Introduction Parallel excitation employs multiple transmit channels and coils, each driven by independent waveforms, to afford the pulse designer an additional spatial encoding mechanism, i.e., transmit sensitivity encoding, that complements gradient encoding. However, in contrast to parallel reception, parallel excitation requires individual high-power amplifiers for each transmit channel, whi...