Improved shimming for fMRI specifically optimizing the local BOLD sensitivity.
In functional MRI, magnetic field inhomogeneities due to air-tissue susceptibility differences may lead to severe signal dropouts and geometric distortions in echo-planar images. Therefore, the inhomogeneities in the field are routinely minimized by shimming prior to imaging. However in fMRI, the Blood Oxygen Level Dependent (BOLD) effect is the measure of interest, so the BOLD sensitivity (BS) should be optimized rather than the magnetic field homogeneity. The analytical expression for an estimate of the BOLD sensitivity has been recently developed, allowing for the computation of BOLD sensitivity maps from echo-planar images and field maps. This report describes a novel shimming procedure that optimizes the local BOLD sensitivity over a region of interest. The method is applied in vivo and compared to a standard global shimming procedure. A breath-holding experiment was carried out and demonstrated that the BS-based shimming significantly improved the detection of activation in a target region of interest, the medial orbitofrontal cortex.
Balteau
Evelyne
E
Cyclotron Research Centre, Liège University, Liège, Belgium. e.balteau@ulg.ac.be
Hutton
Chloe
C
Weiskopf
Nikolaus
N
D000465:Algorithms; D003198:Computer Simulation; D004574:Electromagnetic Fields; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000706:statistics & numerical data; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D010100:Oxygen / Q000097:blood*; D015656:Respiratory Mechanics / Q000502:physiology; D012984:Software
D010100:Oxygen
Magn Reson Med. 2002 Oct;48(4):715-22
12353290
J Neurosci. 2009 Feb 11;29(6):1648-56
19211872
Magn Reson Med. 2003 Mar;49(3):409-16
12594742
MAGMA. 2008 Mar;21(1-2):31-40
18180969
Magn Reson Med. 1999 Aug;42(2):290-9
10440954
PLoS One. 2009;4(3):e5091
19333398
Hum Brain Mapp. 2002 Nov;17(3):143-55
12391568
Neuroimage. 2001 May;13(5):903-19
11304086
Neuroimage. 2005 Mar;25(1):112-21
15734348
MAGMA. 2007 Feb;20(1):39-49
17268781
J Magn Reson. 2000 Aug;145(2):184-91
10910686
Stroke. 1998 Dec;29(12):2641-5
9836778
Neuroimage. 2006 Nov 1;33(2):493-504
16959495
Magn Reson Med. 1997 Mar;37(3):331-5
9055220
Neuroimage. 2005 May 15;26(1):243-50
15862224
Neuroimage. 2002 Jan;15(1):120-35
11771980
Magn Reson Med. 2008 Jan;59(1):221-7
18050341
Magn Reson Med. 1999 Jul;42(1):110-7
10398956
Magn Reson Med. 1991 Jul;20(1):113-22
1943653
Magn Reson Med. 1991 Apr;18(2):335-47
2046515
Magn Reson Med. 2005 May;53(5):1046-54
15844094
Magn Reson Med. 2001 Apr;45(4):595-604
11283987
Magn Reson Med. 1996 Jul;36(1):159-65
8795035
Magn Reson Med. 1993 Jun;29(6):804-11
8350724
Neuroimage. 1995 Sep;2(3):173-81
9343600
J Magn Reson Imaging. 1999 Apr;9(4):531-8
10232510
Neuroimage. 2002 May;16(1):217-40
11969330
Neuroimage. 2002 Oct;17(2):967-76
12377170
Magn Reson Med. 2001 Oct;46(4):631-7
11590638
Neuroimage. 2003 Jun;19(2 Pt 1):430-41
12814592
Magn Reson Imaging. 2001 Jan;19(1):13-20
11295341
Magn Reson Med. 2005 Aug;54(2):373-85
16032676
Neuroimage. 2004 Feb;21(2):757-67
14980579
Magn Reson Med. 1996 Mar;35(3):346-55
8699946