Whole body 3T MRI system with eight parallel RF transmit/receive channels and dual operation modes

I. Graesslin; P. Vernickel; J. Schmidt; C. Findeklee; P. Röschmann; C. Leussler; P. Haaker; H. Laudan; K. M. Luedeke; J. Scholz; S. Buller; J. Keupp; P. Börnert; H. Dingemans; G. Mens; G. Vissers; K. Blom; Jvd Heijden; N. Swennen; L. Mollevanger; P. Harvey; U. Katscher

doi:10.1055/s-2007-972138

RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, Inhaltsverzeichnis

Whole body 3T MRI system with eight parallel RF transmit/receive channels and dual operation modes

I Graesslin ¹, P Vernickel ², J Schmidt ¹, C Findeklee ¹, P Röschmann ¹, C Leussler ¹, P Haaker ¹, H Laudan ¹, KM Luedeke ¹, J Scholz ¹, S Buller ¹, J Keupp ¹, P Börnert ¹, H Dingemans ³, G Mens ³, G Vissers ³, K Blom ³, J vd Heijden ³, N Swennen ³, L Mollevanger ³, P Harvey ³, U Katscher ¹

¹Philips Research Europe, Hamburg, Germany
²TuTech Innovation, Hamburg, Germany
³Philips Medical Systems, Best, The Netherlands

Abstract

Whole body imaging at 3T and above may be disturbed by B1 field inhomogeneity caused by wave propagation effects. Simulations [1] have shown that RF shimming techniques can compensate such inhomogeneities. Furthermore, the acceleration of 2/3D spatially selective excitations enables new and/or improved technical features like zoom imaging, navigators or arterial spin labeling and other advanced parallel transmission techniques [2–4].

This paper describes the first fully integrated MRI prototype system based on a standard commercial 3T Philips MRI scanner, which features a fully integrated multi-element body coil (MBC) as well as an integrated control and data acquisition system (CDAS).

A single- and multi-channel RF transmit mode was implemented. In the multi-transmit mode, the individual RF signals of the eight independent transmitters (Tx1-Tx8, Fig.1, blue) are amplified by individual solid-state RF amplifiers. For patient safety reasons, a shutdown unit (SDU) prevents RF transmission if any of the eight transmit channels fails. The RF signals are routed via individual circulators and transmit/receive switches to the Tx/Rx TEM resonators of a MBC. In the single-channel mode, a circularly polarized B1-field is generated by using transmitter board Tx, a single RF-amplifier, a RF power splitter, and phase shifters (Fig.1, orange).

Parallel phantom and in-vivo experiments were carried out using parallel transmission (TxSENSE with reduction factors R=1...8) as well as reception (RxSENSE factors up to 4).

References:

1. Ibrahim TS et al. [2000] MRI 18:733–742.

2. Katscher U et al. [2003] MRM 49:144–150.

3. Zhu Y [2004] MRM 51:775–784.

4. Grissom W et al. [2005] ISMRM 13:19

Fig.1: Block diagram of an eight-channel Tx/Rx MR system architecture with two operation modes.