Diffusion tensor imaging and fiber tractography of the median nerve at 1.5T: optimization of b value.
OBJECTIVE
The objective of this study was to systematically assess the optimal b value for diffusion tensor imaging and fiber tractography of the median nerve at 1.5 T.


METHODS
This is a prospective study which was carried out with institutional review board approval and written informed consent from the study subjects. Fifteen healthy volunteers (seven men, eight women; mean age, 31.2 years) underwent diffusion tensor imaging of the wrist. A single-shot spin-echo-based echo-planar imaging sequence (TR/TE, 7000/103 ms) was performed in each subject at eight different b values ranging from 325 to 1,550 s/mm(2). Number and length of reconstructed fiber tracts, fiber density index (FDi), fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were calculated for the median nerve. Signal-to-noise ratio (SNR) was also calculated for each acquisition. The overall image quality was assessed by two readers in consensus by ranking representative fiber tract images for each subject using a scale range from 1 to 8 (1 = best to 8 = worst image quality).


RESULTS
Longest fibers were observed for b values between 675 and 1,025 s/mm(2). Maximum FDi was found at b values of 1,025 s/mm(2). FA was between 0.5 and 0.6 for all b values. ADC gradually decreased from 1.44 x 10(-3) to 0.92 x 10(-3) mm(2)/s with increasing b values. Maximum SNR +/- standard deviation (175.4 +/- 72.6) was observed at the lowest b value and decreased with increasing b values. SNR at b values of 1,025 s/mm(2) was 48.5% of the maximum SNR. Optimal fiber tract image quality was found for b values of 1,025 s/mm(2).


CONCLUSIONS
The optimal b value for diffusion tensor imaging and fiber tractography of the median nerve at 1.5 T was 1,025 s/mm(2).
Andreisek
Gustav
G
Division of Musculoskeletal Imaging, Department of Medical Imaging, Mount Sinai Hospital and the University Health Network, University of Toronto, 600 University Ave, Toronto, Ontario, Canada, M5G 1X5. gustav@andreisek.de
White
Lawrence M
LM
Kassner
Andrea
A
Tomlinson
George
G
Sussman
Marshall S
MS
D000328:Adult; D016880:Anisotropy; D003430:Cross-Sectional Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008475:Median Nerve / Q000033:anatomy & histology*; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D009434:Neural Pathways / Q000033:anatomy & histology*; D011446:Prospective Studies
Anat Rec. 1999 Jun 15;257(3):102-9
10397783
Magn Reson Imaging. 2007 Apr;25(3):406-11
17371732
Magn Reson Med. 2001 Mar;45(3):448-53
11241703
Radiology. 2003 Sep;228(3):603-8
12881587
Magn Reson Med. 2004 Feb;51(2):230-6
14755645
Neuroimage. 2008 Jan 1;39(1):119-26
17931889
Magn Reson Med. 2002 Jul;48(1):97-104
12111936
Eur J Radiol. 2003 Apr;46(1):53-66
12648802
NMR Biomed. 2002 Nov-Dec;15(7-8):468-80
12489096
Eur Radiol. 2007 Dec;17(12):3079-85
17639406
Exp Neurol. 2006 Apr;198(2):479-82
16455078
Magn Reson Imaging. 2004 Jun;22(5):743-5
15172070
IEEE Trans Med Imaging. 2007 Nov;26(11):1428-36
18041258
Magn Reson Med. 2004 Sep;52(3):559-65
15334575
Magn Reson Med. 2005 Aug;54(2):393-401
16032670
J Magn Reson Imaging. 2007 Sep;26(3):756-67
17729339
Clin Neurophysiol. 2005 Oct;116(10):2315-23
16125460
J Appl Physiol (1985). 2007 Aug;103(2):673-81
17446411
Eur J Radiol. 2003 Mar;45(3):223-34
12595107
J Magn Reson Imaging. 2006 Aug;24(2):402-8
16823776
J Magn Reson Imaging. 2006 Nov;24(5):1005-10
17031835
Rofo. 2007 Mar;179(3):219-24
17325991
Magn Reson Imaging. 1998 Sep;16(7):773-85
9811143
Med Phys. 1985 Mar-Apr;12(2):232-3
4000083
AJNR Am J Neuroradiol. 2005 Oct;26(9):2183-6
16219820
Radiology. 2007 Nov;245(2):367-84
17940300
Acta Radiol. 2006 Jul;47(6):599-602
16875339
Comput Methods Programs Biomed. 2006 Feb;81(2):106-16
16413083
Proc Natl Acad Sci U S A. 1996 Nov 12;93(23):13429-34
8917608
AJR Am J Roentgenol. 2007 Oct;189(4):923-7
17885066
Neuron. 2006 Sep 7;51(5):527-39
16950152
Radiographics. 2005 Jan-Feb;25(1):53-65; discussion 66-8
15653586
Neuroimage. 2007 Jul 15;36(4):1123-38
17532649