Principles and concepts of gradient echo (GRE) imaging are the basis of many applications on modern MR-systems. The most obvious difference between Spin Echo and GRE imaging is related to the pulse sequence elements that are used to generate an MR signal (see figure 1). While two rf-pulses (90 and 180) are used for spin refocusing and spin echo generation, GRE imaging is based on only a single ...

We have developed radiofrequency coils for high-field head and whole-body imaging which achieve near optimal rf field (Br) homogeneity and signal-to-noise ratio (SNR). The design, based on a lumped element delay line, has a number of advantages. The rf field uniformity is significantly better than that of a saddle coil or slotted tube resonator. The improved Br homogeneity is needed to generate...

Improvements in signal to noise ratio (SNR) and ease of use of magnetic resonance imaging (MRI) rf coils are needed to improve image quality and patient throughput in high-field MRI. The goal of this Phase II project is to continue the development of novel rf coil topologies and rf balancing circuits that have demonstrated substantially improved technical performance, reduced cost, and greatly ...

Background Conventional MRI scanners up to a magnetic field strength of 3T use an integrated birdcage quadrature coil to generate a radio frequency (RF) excitation field (B1+). At 3T, Sung et al. observed a flip angle variation ranging from 31 to 66% over the entire left ventricle (LV) in humans as well as a flip-angle distribution from 34° to 63, for a nominal flip angle of 60°. This not only ...

The purpose of this study was to assess the effects of contraction intensity, gender, and muscle on median frequency of the three superficial portions of the quadriceps femoris muscle. Thirty healthy volunteers were assessed for isometric electromyogram activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles with the knee at 60 degrees flexion. Subjects perf...

The use of detached endcaps for 3 T birdcage coils was investigated both theoretically and experimentally. Finite difference time domain analysis, along with workbench and MRI techniques, were used to map the radiofrequency (RF) B(1) distribution along the coil axis with and without an endcap. Without an endcap the measured B(1) value at the service end of the birdcage was only 45% of the value...

Introduction Simultaneous multi-slice (SMS) imaging with receiver arrays allows for greatly accelerated 2D single-shot acquisitions with BOLD or diffusionweighted EPI (1-4), and spirals (5). The commonly used SMS excitation methods require specially designed multi-band (MB) (1,2) or PINS RF pulses (6) to excite N slices. In this abstract we explore the use of parallel transmission (pTX) for SMS...

It has been proposed that the sequences surrounding nonsense codons determine the efficiency of protein-chain termination. To test this hypothesis, the termination factor, RF-1, was purified to near homogeneity and was used to examine the specificity of in vitro prokaryotic termination as a function of the nature and number of bases adjacent to UAA. Oligomers with different nucleotide sequences...

Introduction Apart from being a non-invasive imaging modality, MR breast imaging can also provide high spatial and temporal resolution images of the breast, which is advantageous for fast and accurate diagnosis of disease. Studies have shown that it is possible to acquire high resolution breast images at ultra high fields with dedicated transceive RF breast coils that can transmit homogenous lo...

Wireless capsule endoscope (WCE) provides a noninvasive method to examine the entire gastrointestinal (GI) tract including small intestine, which other video endoscopic instruments cannot reach. However, since the shape of the small intestine is extremely complex and the length of small intestine varies from 5m to 9m, localization of the capsule inside small intestine is very challenging. Exist...