On-coil multiple channel transmit system based on class-D amplification and pre-amplification with current amplitude feedback.

A complete high-efficiency transmit amplifier unit designed to be implemented in on-coil transmit arrays is presented. High power capability, low power dissipation, scalability, and cost minimization were some of the requirements imposed to the design. The system is composed of a current mode class-D amplifier output stage and a voltage mode class-D preamplification stage.

MRI pulse sequence design with first-order gradient moment nulling in arbitrary directions by solving a polynomial program.

We suggest a polynomial program for the calculation of optimized gradient waveforms for magnetic resonance tomography pulse sequences. Such non-linear mathematical programs can describe gradient system capabilities, meet k-space trajectory specifications, and capture sequence timing conditions. Moreover they allow the incorporation of gradient moment nulling constraints in one or several arbitrary spatial directions, which can reduce flow motion artifacts in the images.

Induction of electric fields due to gradient switching: a numerical approach.

Since the first observations of peripheral nerve stimulation in MRI, it has been clear that the underlying mechanism is the activation of the nervous system by induced electric fields. However, compared to experimental investigations little work has been done on calculating these electric fields with adequate accuracy. In this article a numerical analysis of the electric fields induced by a complete whole body gradient system is presented.

Fast contrast-enhanced MR whole-brain venography.

Our aim was to assess the value of a new fast contrast-enhanced MR venography (CE-MRV) sequence in the investigation of normal and diseased cerebral veins. Conventional time-of-flight (TOF) MRV is time consuming, with imaging for a single sequence taking many minutes. MRI was performed with a clinical 1.