MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography

MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography

Článek WoS

Gradient eddy currents, induced in the surrounding conductive structures in a MR magnet, are a major problem in MRI, in localized MR spectroscopy and in many other MR experiments. We present a comparison of three methods of measuring the gradient time characteristics and the time changes of basic magnetic field B0 after the gradient is switched off. The methods are based on a selective excitation of a thin layer of the specimen and on acquiring the MR signal obtained after the and of the gradient pulse and on the computation of the instantaneous frequency of the signal. At this point, the time gradient characteristic is proportional to the instantaneous frequency of the MR signal, which has a small signal to noise (S/N) ratio. We use the characteristics measured to set the pre-emphasis parameters in a 200 MHz/200 mm MR scanner. From the results obtained by measurement it follows that all methods are convenient for simple and quick characterization of gradient magnetic filed in MR tomographic magnets.

Gradient eddy currents, induced in the surrounding conductive structures in a MR magnet, are a major problem in MRI, in localized MR spectroscopy and in many other MR experiments. We present a comparison of three methods of measuring the gradient time characteristics and the time changes of basic magnetic field B0 after the gradient is switched off. The methods are based on a selective excitation of a thin layer of the specimen and on acquiring the MR signal obtained after the and of the gradient pulse and on the computation of the instantaneous frequency of the signal. At this point, the time gradient characteristic is proportional to the instantaneous frequency of the MR signal, which has a small signal to noise (S/N) ratio. We use the characteristics measured to set the pre-emphasis parameters in a 200 MHz/200 mm MR scanner. From the results obtained by measurement it follows that all methods are convenient for simple and quick characterization of gradient magnetic filed in MR tomographic magnets.

MR tomography, gradiernt magnetic field, IF method, IFSE method, IFSES method, spin echo

MR tomography, gradiernt magnetic field, IF method, IFSE method, IFSES method, spin echo

BARTUŠEK, K.; GESCHEIDTOVÁ, E.

01.12.2006

Springer

0937-9347

APPLIED MAGNETIC RESONANCE

29

12

Rakouská republika

675

687

12