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Titolo:
Modeling geometric deformations in EPI time series
Autore:
Andersson, JLR; Hutton, C; Ashburner, J; Turner, R; Friston, K;
Indirizzi:
Wellcome Dept Cognit Neurol, London, England Wellcome Dept Cognit Neurol London England gnit Neurol, London, England
Titolo Testata:
NEUROIMAGE
fascicolo: 5, volume: 13, anno: 2001,
pagine: 903 - 919
SICI:
1053-8119(200105)13:5<903:MGDIET>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
IMAGE REGISTRATION; FUNCTIONAL MRI; MOTION CORRECTION; INTERPOLATION; DISTORTION; FMRI; NORMALIZATION; ARTIFACTS; BRAIN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
23
Recensione:
Indirizzi per estratti:
Indirizzo: Andersson, JLR Karolinska Hosp N8, Karolinska MR Res Ctr, S-17176 Stockholm, Sweden Karolinska Hosp N8 Stockholm Sweden S-17176 kholm, Sweden
Citazione:
J.L.R. Andersson et al., "Modeling geometric deformations in EPI time series", NEUROIMAGE, 13(5), 2001, pp. 903-919

Abstract

Even after realignment there is residual movement-related variance presentin fMRI time-series, causing loss of sensitivity and, potentially, also specificity. One cause is the differential deformation of the sampling matrix, by field inhomogeneities, at different object positions, i.e., a movement-by-inhomogeneity interaction. This has been addressed previously by using empirical field measurements. In the present paper we suggest a forward model of how data is affected by an inhomogeneous field at different object positions. From this model we derive a method to solve the inverse problem ofestimating the field inhomogeneities and their derivatives with respect toobject position, directly from the EPI data and estimated realignment parameters. The field is modeled as a linear combination of cosine basis fields, which facilitates a fast way of implementing the necessary matrix operations. Simulations suggest that the solution is tractable and that the fieldsare estimable given the deformed images and knowledge of the relative positions at which they have been acquired. An experiment on a subject performing voluntary movements in the scanner yielded plausible estimates of the deformation fields and their application to "unwarp" the time series significantly reduced movement-related variance. (C) 2001 Academic Press.

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Documento generato il 19/01/20 alle ore 20:38:44