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The conductivity and permittivity of biological tissue are critical to estimating local radiofrequency (RF) power deposition (also known as specific absorption rate SAR) for Ultra High Field Magnetic Resonance Imaging (UH-MRI). These electrical properties may also have diagnostic value as malignant tissue types have been shown to have higher permittivity and conductivity than surrounding healthy tissue...
With the reduced radio frequency wavelength at Ultrahigh field magnetic resonance imaging (MRI) scanner, traditional volume-type RF hardware suffers from the standing wave effect and leads to RF artefacts, e.g. inhomogeneity in the magnetic field, and signal losses of MR images. Travelling wave excitation is proposed recently to utilize the waveguide effect of the magnet bore to achieve a homogeneous...
The electromagnetic (EM) simulation guided design and operation of a receive-only liquid nitrogen (LN2) cooled coil suitable for medical imaging on a 3-T whole body MR scanner is presented. This process is easier and more cost-effective than building a range of coils. The performance of the designed probe was evaluated by comparison of signal-to-noise ratio (SNR) with the same radio-frequency (RF)...
With the recent development of high field MRI scanners, the risk for healthcare staff being exposed to large static magnetic fields (3T to 7T) and rapidly time-varying magnetic field gradients is greatly increased. A better understanding of the interaction mechanisms and the bio-effects associated with MRI environment would allow sensible and workable exposure limits to be set for staff, patients...
This paper compares three different modelling techniques applied to the problem of field propagation through time-varying media. Each method is representative of a particular class of methods, namely analytical, semi-analytical and numerical methods. The accuracy, stability, strengths and limitations of each method will be discussed on time-varying one-dimensional and two dimensional problems
Recently, second harmonic (SH) generation and its enhancement in one-dimensional (1D) photonic bandgap (PBG) structures has received growing interest. The 1D PBG grating has been proposed as a mean to achieve enhanced SH conversion efficiency by using the combined effects of the increased mode density at the transmission band edge, strong field localization, and the phase matching condition
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