Parallel transmission has gained considerable interest during the last few years [1,2]. The use of multiple individual RF transmit coils have been introduced to overcome B1 homogeneity limitations and to improve multi-dimensional RF pulses by shortening their duration. Of special concern in all these transmit applications is the specific absorption rate (SAR), which has to be kept below certain...

Chemical exchange saturation transfer magnetic resonance imaging (CEST-MRI) is capable of both microenvironment and molecular imaging. The optimization of scanning parameters is important since the CEST effect is sensitive to factors such as saturation power and field homogeneity. The aim of this study was to determine if the CEST effect would be altered by changing the length of readout RF pul...

Introduction In RF shimming [1,2], a single RF current waveform is modulated in amplitude and phase at each coil of a transmit array, in order to control the distribution of electromagnetic (EM) fields and compensate for B1 inhomogeneities. An algorithm to minimize the specific absorption rate (SAR) for a given target profile using RF shimming has been recently proposed and evaluated in simulat...

A spectroscopic imaging technique with high spatial resolution was used for the measurement of the static magnetic field homogeneity of RF coils. Measured magnetic fields of optimised and not optimised saddle-shaped coils were compared with the theoretical calculations. Results are in good qualitative agreement between calculated and measured magnetic field distributions. Quantitative disagreem...

Integration of high-resolution nuclear magnetic resonance (NMR) spectroscopy with microfluidic lab-on-a-chip devices is challenging due to limited sensitivity and line broadening caused by magnetic susceptibility inhomogeneities. We present a novel double-stripline NMR probe head that accommodates planar microfluidic devices, and obtains the NMR spectrum from a rectangular sample chamber on the...

The paper is concerned with a comparison of the properties of RF coils of three configurations for MRI measurements on small animals. In comparison with the classical saddle coil the proposed modification of slotted-tube coil exhibits identical homogeneity of B1 field in a larger space. The parallel-plate coil has a satisfactory homogeneity of B1 field over the whole internal space. The signal-...

A spatially resolved extended phase graph (SR-EPG) framework is proposed for prediction of echo amplitudes in the presence of spatially variable radio frequency (RF) fields. The method may be used to examine any regularly repeating pulse sequence and provides a design framework for parallel transmission (PTx) systems; in this work signal homogeneity in static pseudo-steady state (SPSS) turbo sp...

Introduction Electromagnetic wave propagation in tissue is known to cause dielectric resonance effects if the wavelength reaches the object dimension. At 3.0T, dielectric resonance effects are visible in body MR imaging predominantly in heavier patients and in patients with intraabdominal fluid collections (i.e. ascites). The use of multiple transmit channels can provide better control of the r...

A method for calculating B1 field strength and homogeneity In order to construct an optimal RF system, it is important as functions of radiofrequency shield geometry is presented. The to consider how shield geometry will affect the performance method requires use of three-dimensional finite-element analysis, of the RF system. It is possible to measure B1 field strength birdcage-coil theory, and...