In high-field magnetic resonance imaging, the radio frequency wavelength within the human body is comparable to anatomical dimensions, resulting in B1 inhomogeneity and nonuniform sensitivity patterns. Thus, this relatively short wavelength presents engineering challenges for RF coil design. In this study, a bilateral breast coil for 1H imaging at 7 T was designed and constructed using forced-current excitation. By forcing equal current through the coil elements, we reduce the effects of coupling between the elements to simplify tuning and to ensure a uniform field across both breasts. To combine the benefits of the higher power efficiency of a unilateral coil with the bilateral coverage of a bilateral coil, a switching circuit was implemented to allow the coil to be reconfigured for imaging the left, right, or both breasts.

This paper reports our results in developing a simple MRI system for teaching the basics of MR Engineering at the undergraduate or graduate level. LabVIEW data acquisition cards were used for generating and digitizing the RF signals and controlling gradients and transmit/receive and blanking switches. A very inexpensive and simple magnet reported previously by Sahakian was used to enable simple, projection reconstruction imaging. Students constructed the gradients, RF coils and did system level assembly and programming of the data acquisition system. At the end of the course students were tasked with identifying unknown imaging "phantoms" in their magnet, and then improving the image based on their knowledge.

MRI of flow remains a challenging problem despite significant improvements in imaging speeds. For periodic flow the acquisition can be gated, synchronizing data acquisition with the flow. However, this method fails to work if the flow is sufficiently fast that turbulence occurs, or when it is sufficiently fast that blurring occurs during the excitation of the spins or the acquisition of the signal. This paper describes recent progress in employing a very fast MR imaging technique, Single Echo Acquisition Imaging (SEA-MRI) and spin-tagging to visualize very rapid and turbulent flow patterns. Demonstrations are done on a separating channel phantom with input flow rates ranging from zero to over 100 cm/sec. Spin-tagging enables a "texture" to be placed on the spins, enabling clear visualization of the complex flow patterns, and in some cases measurement of the flow velocity.

In magnetic resonance imaging with array coils with many elements, as the radiofrequency (RF) coil dimensions approach the voxel dimensions, the phase gradient due to the magnetic field pattern of the coil causes signal cancellation within each voxel. In single echo acquisition (SEA) imaging with coil arrays, a gradient pulse can be applied to compensate for this effect. However, because RF coil phase varies with distance from the array and reverses on opposite sides of a dual-sided array, this method of phase compensation can be optimized for only a single slice at a time. In this study, a nonlinear gradient coil was implemented to provide spatially varying phase compensation to offset the coil phase with slice position for dual-sided arrays of narrow coils. This nonlinear gradient coil allows the use of one phase compensation pulse for imaging multiple slices through a slab, and, importantly, is shown to enable simultaneous SEA imaging from opposite sides of a sample using a dual-sided receive array.