"675-686" . . . "MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography" . "26220" . . "Z(AV0Z20650511), Z(MSM0021630513), Z(MSM0021630516)" . "MR m\u011B\u0159ic\u00ED techniky rychle p\u0159ep\u00EDnan\u00FDch gradientn\u00EDch magnetick\u00FDch pol\u00ED v MR tomografii"@cs . . "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."@en . "MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography" . "487175" . "12" . "MR m\u011B\u0159ic\u00ED techniky rychle p\u0159ep\u00EDnan\u00FDch gradientn\u00EDch magnetick\u00FDch pol\u00ED v MR tomografii"@cs . "2"^^ . . . . "MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography"@en . "AT - Rakousk\u00E1 republika" . . "2"^^ . . "0937-9347" . "MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography"@en . "Gescheidtov\u00E1, Eva" . . "V\u00ED\u0159iv\u00E9 proudy indukovan\u00E9 v bl\u00EDzkosti vodiv\u00FDch \u010D\u00E1st\u00ED MR magnetu p\u0159edstavuj\u00ED hlavn\u00ED probl\u00E9m v MR zobrazov\u00E1n\u00ED, MR spektroskopii a mnoha dal\u0161\u00EDch experimentech. V \u010Dl\u00E1nku je prezentov\u00E1no srovn\u00E1n\u00ED t\u0159\u00ED metod m\u011B\u0159en\u00ED \u010Dasov\u00FDch charakteristik gradientn\u00EDch magnenticn\u00FDch pol\u00ED a \u010Dasov\u00E9 z\u00E1vislosti magnetick\u00E9ho pole B0 po vypnut\u00ED gradient\u016F. Metody jsou zalo\u017Eeny na selektivn\u00ED excitaci tenk\u00E9 vrstvy vzorku a sn\u00EDm\u00E1n\u00ED MR sign\u00E1lu na konci gradientn\u00E9h impulzu, d\u00E1le na v\u00FDpo\u010Dtu okam\u017Eit\u00E9ho kmito\u010Dtu sign\u00E1lu a n\u00EDzk\u00FDch pom\u011Brem S/N. Zm\u011B\u0159en\u00E9 charakteristiky jsou pou\u017Eity k nastaven\u00ED peeemf\u00E1fov\u00FDch filtr\u016F 200 MHz/200 mm MR p\u0159\u00EDstroje. Ze z\u00EDskan\u00FDch v\u00FDsledk\u016F plyne, \u017Ee v\u0161echny t\u0159i metoyd jsou vhodn\u00E9 k jednoduch\u00E9mu a rychl\u00E9mu m\u011B\u0159en\u00ED charakteristoik gradientn\u00EDch pol\u00ED v magnetech MR tomograf\u016F."@cs . "RIV/00216305:26220/06:PU54874!RIV07-MSM-26220___" . . . "[ADB5C4471618]" . . "12"^^ . "MR tomography, gradiernt magnetic field, IF method, IFSE method, IFSES method, spin echo"@en . . "Applied Magnetic Resonance (IF 0,665)" . . . "Bartu\u0161ek, Karel" . . . "RIV/00216305:26220/06:PU54874" . . . . "29" . "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." .