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| Description
| - 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. (en)
- Vířivé proudy indukované v blízkosti vodivých částí MR magnetu představují hlavní problém v MR zobrazování, MR spektroskopii a mnoha dalších experimentech. V článku je prezentováno srovnání tří metod měření časových charakteristik gradientních magnenticných polí a časové závislosti magnetického pole B0 po vypnutí gradientů. Metody jsou založeny na selektivní excitaci tenké vrstvy vzorku a snímání MR signálu na konci gradientnéh impulzu, dále na výpočtu okamžitého kmitočtu signálu a nízkých poměrem S/N. Změřené charakteristiky jsou použity k nastavení peeemfáfových filtrů 200 MHz/200 mm MR přístroje. Ze získaných výsledků plyne, že všechny tři metoyd jsou vhodné k jednoduchému a rychlému měření charakteristoik gradientních polí v magnetech MR tomografů. (cs)
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| Title
| - MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography
- MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography (en)
- MR měřicí techniky rychle přepínaných gradientních magnetických polí v MR tomografii (cs)
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| skos:prefLabel
| - MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography
- MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography (en)
- MR měřicí techniky rychle přepínaných gradientních magnetických polí v MR tomografii (cs)
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| skos:notation
| - RIV/00216305:26220/06:PU54874!RIV07-MSM-26220___
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| http://linked.open.../vavai/riv/strany
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| http://linked.open...avai/riv/aktivita
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| http://linked.open...avai/riv/aktivity
| - Z(AV0Z20650511), Z(MSM0021630513), Z(MSM0021630516)
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| http://linked.open...iv/cisloPeriodika
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| http://linked.open...vai/riv/dodaniDat
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| http://linked.open...aciTvurceVysledku
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| http://linked.open.../riv/druhVysledku
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| http://linked.open...iv/duvernostUdaju
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| http://linked.open...titaPredkladatele
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| http://linked.open...dnocenehoVysledku
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| http://linked.open...ai/riv/idVysledku
| - RIV/00216305:26220/06:PU54874
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| http://linked.open...riv/jazykVysledku
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| http://linked.open.../riv/klicovaSlova
| - MR tomography, gradiernt magnetic field, IF method, IFSE method, IFSES method, spin echo (en)
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| http://linked.open.../riv/klicoveSlovo
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| http://linked.open...odStatuVydavatele
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| http://linked.open...ontrolniKodProRIV
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| http://linked.open...i/riv/nazevZdroje
| - Applied Magnetic Resonance (IF 0,665)
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| http://linked.open...in/vavai/riv/obor
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| http://linked.open...ichTvurcuVysledku
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| http://linked.open...cetTvurcuVysledku
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| http://linked.open...UplatneniVysledku
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| http://linked.open...v/svazekPeriodika
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| http://linked.open...iv/tvurceVysledku
| - Bartušek, Karel
- Gescheidtová, Eva
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| http://linked.open...n/vavai/riv/zamer
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| issn
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| number of pages
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| http://localhost/t...ganizacniJednotka
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| is http://linked.open...avai/riv/vysledek
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