INTRODUCTION Recently, an anatomically shaped helmet coil consisting of four curved microstrip transmission-line (MTL) elements was introduced (1). The MTL elements were combined either as a circularly polarized (CP) transmit/receive (Tx/Rx) coil (Type A) or as a CP transmit, four-channel receive array (Type B). Both types provided an almost perfect circular polarization in the central region a...

Both the optimization of B1 field homogeneity in high-field MRI and the implementation of the exciting new theory of transmit SENSE can be accomplished by individual and independent control of the amplitude and phase of current on the elements or rungs of a radio frequency (RF) transmit coil array. One way of achieving this is by using the concept of the active rung, which consists of one rung ...

Signal-to-noise ratio (SNR), RF field (B(1)), and RF power requirement for human head imaging were examined at 7T and 4T magnetic field strengths. The variation in B(1) magnitude was nearly twofold higher at 7T than at 4T ( approximately 42% compared to approximately 23%). The power required for a 90 degrees pulse in the center of the head at 7T was approximately twice that at 4T. The SNR avera...

Introduction: Counteracting the inhomogeneity of the RF excitation is one of the technical challenges in high-field MRI. Dynamic RF shimming techniques in combination with parallel transmission have shown to be quite powerful for mitigating B1 inhomogeneity [1, 2]. So far to our knowledge, these methods have been uniquely based on the spins’ coherent dynamics, and do not account for relaxation ...

In this work, we propose a method to improve electro-optical and structural parameters of light-absorbing kesterite materials. It relies on the application of weak power hydrogen plasma discharges using electromagnetic field of radio frequency range, which improves homogeneity of the samples. The method allows to reduce strain of light absorbers and is suitable for designing solar cells based o...

A surface coil is any radiofrequency (RF) coil placed directly on the surface of the subject. Surface coils represent some of the simplest coil designs used in magnetic resonance, but are commonly used in experiments requiring the highest possible sensitivity. In contrast to volume coils, which are designed to provide homogeneous sensitivity over the whole field-of-view, surface coils sacrifice...

The PSIF (gradient-reversed FISP, SSFP, CE-FAST) sequence is demonstrated to produce high-quality, T,-weighted images in human brain at magnetic field strengths of 4 Tesla and above In contrast to spin-echo or multiple-echo imaging techniques commonly used in clinical practice at lower fields, the importance of Bi homogeneity in PSIF imaging is minimal and the average RF power deposition is low...

shimming. Right: 10gm average RF absorption or SAR for H(1)-(4) for the same B1+ shimming, and mean B1+ of 2.5uT in the brain. Table 1 shows the stats on B1+ and sample SAR variation across subjects for the same B1+ shimming amplitudes and phases. The homogeneity, SAR ave and peak changes were <10 % across the 4 head models H(1)-(4). Figure 1 The Tx array tuning (Smith Chart) on 3 volunteers (d...

Introduction Correction of B1 inhomogeneities and management of SAR are among the most difficult challenges faced by in-vivo ultra high field MR applications. The use of multiple independently driven transmit elements, which enables fine control over the distribution of electromagnetic fields, has been explored as a possible solution and various approaches have been developed. In parallel trans...