The choice of TE for BOLD fMRI also depends on other factors, such as
signal dropout in brain areas affected by large susceptibility gradients.
Ideally TE should be equal to T2* to give maximum BOLD contrast, as was
realized back in 1992 by the earliest BOLD researchers, but long TE's can
give unacceptable 'holes' in the image, paricularly in lower axial
sections. We use a TE of 40 ms (at 2T), which represents a reasonable
compromise.
Bob Turner
>That's correct about increasing TE.
>At 1.5T, you should actually use a TE of ~60ms to maximize your % signal
>change.
>This decreases to ~30ms at 4T.
>An M.Sc student at our lab showed this in his thesis, and I believe the
>work is actually published now.
>Sincerely,
>CHris Thomas
>Date: Thu, 1 Oct 1998 08:26:21 -0400
>Encoding: 54 TEXT
>Subject: RE: realignment problem
>From: Luis Hernandez <[log in to unmask]>
>To: "[log in to unmask]" <[log in to unmask]>
>X-Unsub: To leave, send text 'leave spm' to [log in to unmask]
>Reply-To: Luis Hernandez <[log in to unmask]>
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>Precedence: list
>
>This is unrelated to your question, but you might find useful that, if you
>increase your TE from 20 ms to 40 - 50 ms on your next experiments, your
>BOLD contrast signal will increase significantly (I'm assuming it's a 1.5
>T magnet). There are several studies, showing this TE dependence (I don't
>recall the references, but if you are interested I can dig them up), and it
>made a big difference for us. I hope this is helpful.
>
>Luis,
>------------------
>Luis Hernandez, Ph.D.
>Research Fellow
>Dept. of Neurosurgery
>Wake Forest University School of Medicine
>Medical Center Blvd.
>Winston Salem, NC 27157
>Phone: (336) 713 8068
>Fax: (336) 713 8588
>
Professor Robert Turner
Wellcome Principal Research Fellow
Wellcome Department of Cognitive Neurology
Institute of Neurology
Queen Square
London WC1N 3BG
Tel: +44 (171) 833-7452
Fax: +44 (171) 813-1445
www: http://www.fil.ion.ucl.ac.uk
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