当前位置： SCI文献检索 > NMR IN BIOMEDICINE期刊下所有文献 > Concurrent recording of RF pulses and gradient fields - comprehensive field monitoring for MRI.

Concurrent recording of RF pulses and gradient fields - comprehensive field monitoring for MRI.

Abstract：

:Reconstruction of MRI data is based on exact knowledge of all magnetic field dynamics, since the interplay of RF and gradient pulses generates the signal, defines the contrast and forms the basis of resolution in spatial and spectral dimensions. Deviations caused by various sources, such as system imperfections, delays, eddy currents, drifts or externally induced fields, can therefore critically limit the accuracy of MRI examinations. This is true especially at ultra-high fields, because many error terms scale with the main field strength, and higher available SNR renders even smaller errors relevant. Higher baseline field also often requires higher acquisition bandwidths and faster signal encoding, increasing hardware demands and the severity of many types of hardware imperfection. To address field imperfections comprehensively, in this work we propose to expand the concept of magnetic field monitoring to also encompass the recording of RF fields. In this way, all dynamic magnetic fields relevant for spin evolution are covered, including low- to audio-frequency magnetic fields as produced by main magnets, gradients and shim systems, as well as RF pulses generated with single- and multiple-channel transmission systems. The proposed approach permits field measurements concurrently with actual MRI procedures on a strict common time base. The combined measurement is achieved with an array of miniaturized field probes that measure low- to audio-frequency fields via (19) F NMR and simultaneously pick up RF pulses in the MRI system's (1) H transmit band. Field recordings can form the basis of system calibration, retrospective correction of imaging data or closed-loop feedback correction, all of which hold potential to render MRI more robust and relax hardware requirements. The proposed approach is demonstrated for a range of imaging methods performed on a 7 T human MRI system, including accelerated multiple-channel RF pulses. Copyright © 2015 John Wiley & Sons, Ltd.

journal_name

NMR Biomed

journal_title

NMR in biomedicine

authors

Brunner DO,Dietrich BE,Çavuşoğlu M,Wilm BJ,Schmid T,Gross S,Barmet C,Pruessmann KP

doi

10.1002/nbm.3359

subject

Has Abstract

pub_date

2016-09-01 00:00:00

pages

1162-72

issue

eissn

0952-3480

issn

1099-1492

journal_volume

pub_type

杂志文章

在线工具

Concurrent recording of RF pulses and gradient fields - comprehensive field monitoring for MRI.