introduction: one of the major causes of image non-uniformity in mri is due to the existence of  non-homogeneity in rf receive and transmit. this can be the most effective source of error in  quantitative  studies  in  mri  imaging.  part  of  this  non-homogeneity  demonstrates  the  characteristics of rf coil and part of it is due to the interaction of rf field with the material being  imaged...

Introduction: One of the major causes of image non-uniformity in MRI is due to the existence of  non-homogeneity in RF receive and transmit. This can be the most effective source of error in  quantitative  studies  in  MRI  imaging.  Part  of  this  non-homogeneity  demonstrates  the  characteristics of RF coil and part of it is due to the interaction of RF field with the material being  imaged...

BACKGROUND Radiofrequency (RF) shading artifacts degrade image quality while performing cardiovascular magnetic resonance (CMR) at higher field strengths. In this article, we sought to evaluate the effect of local RF (B1 field) shimming by using a dual-source-transmit RF system for cardiac cine imaging and to systematically evaluate the effect of subject body type on the B1 field with and witho...

The design and performance of an inductively fed low-pass birdcage radiofrequency (RF) coil for applications at 9.4 T are described where tuning is accomplished by mechanically moving a concentric RF shield about the longitudinal axis of an RF coil. Moving the shield about the RF coil effectively changes the mutual inductance of the system, providing a mechanism for adjusting the resonant frequ...

Dielectric resonance effects and radio-frequency (RF) power deposition have become challenging issues for magnetic resonance imaging at ultrahigh-field (UHF) strengths. The use of transmit (Tx) coil arrays with independently-driven RF sources using a parallel transmission system is a promising method for alleviating the resulting RF inhomogeneities. In this study, the effect on homogeneity and ...

BACKGROUND Dual-channel transmit technology improves the image quality in cardiovascular magnetic resonance (CMR) at 3 T by reducing the degree of radiofrequency (RF) shading over the heart by using RF shimming. Further improvements in image quality have been shown on a dual-transmit system using high permittivity pads. The aim of this study is to investigate the transmit field (B 1 (+)) homoge...

OBJECTIVES To prospectively evaluate the impact of 3.0 T Cardiac MR imaging using dual-source parallel radiofrequency (RF) transmission with patient-adaptive B1 shimming compared with single-source RF transmission in the RF homogeneity, image contrast and image quality. METHODS The study was approved by the local institutional review board, and all subjects provided written informed consent. ...

A number of methods to improve excitation homogeneity in high-field MRI have been proposed, and some of these methods rely on separate control of radiofrequency (RF) coils in a transmit array. In this work we combine accurate RF field calculations and the Bloch equation to demonstrate that by using a sequence of pulses with individually optimized current distributions (i.e., an array-optimized ...

Introduction: Parallel RF excitation is a novel technology that can significantly accelerate multidimensional selective excitation, improve RF homogeneity and reduce SAR. High-fidelity excitation requires accurate knowledge of the transmit array B1 sensitivity profiles and a linear RF transmit system. We present an approach using vector decoupling [1] to facilitate measurement of the B1 sensiti...

Target audience: Researchers and engineers who have interest in RF transmit technology in high field MRI. Purpose: The B1 inhomogeneity is one of the problems for breast imaging at 3 T. Various methods using multiple channel RF transmit coil or using some additional dielectric absorptive material are investigated to overcome this problem [1, 2]. These studies showed the number of channels of RF...