Reducing inhomogeneity artifacts in functional MRI of human brain activation-thin sections vs gradient compensation.
J Magn Reson
; 145(2): 184-91, 2000 Aug.
Article
en En
| MEDLINE
| ID: mdl-10910686
We evaluated two methods for correcting inhomogeneity-induced signal losses in magnetic resonance gradient-echo imaging that either use gradient compensation or simply acquire thin sections. The strategies were tested in the human brain in terms of achievable quality of T2*-weighted images at the level of the hippocampus and of functional activation maps of the visual cortex. Experiments were performed at 2.0 T and based on single-shot echo-planar imaging at 2. 0 x 2.0 mm(2) resolution, 4 mm section thickness, and 2.0 s temporal resolution. Gradient compensation involved a sequential 16-step variation of the refocusing lobe of the slice-selection gradient (TR/TE = 125/53 ms, flip angle 15 degrees ), whereas thin sections divided the 4-mm target plane into either four 1-mm or eight 0.5-mm interleaved multislice acquisitions (TR/TE = 2000/54 ms, flip angle 70 degrees ). Both approaches were capable of alleviating the inhomogeneity problem for structures in the base of the brain. When compared to standard 4-mm EPI, functional mapping in the visual cortex was partially compromised because of a lower signal-to-noise ratio of inhomogeneity-corrected images by either method. Relative to each other, consistently better results were obtained with the use of contiguous thin sections, in particular for a thickness of 1 mm. Multislice acquisitions of thin sections require minimal technical adjustments.
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01-internacional
Base de datos:
MEDLINE
Asunto principal:
Encéfalo
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Imagen por Resonancia Magnética
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Artefactos
Límite:
Adult
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Humans
Idioma:
En
Revista:
J Magn Reson
Asunto de la revista:
DIAGNOSTICO POR IMAGEM
Año:
2000
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Estados Unidos