title: Phase-aligned multiple spin-echo averaging: a simple way to improve signal-to-noise ratio of in vivo mouse spinal cord diffusion tensor image.
abstract: OBJECTIVE
  To improve signal-noise-ratio of in vivo mouse spinal cord diffusion tensor imaging using-phase aligned multiple spin-echo technique.
  
  
  METHODS
  In vivo mouse spinal cord diffusion tensor imaging maps generated by multiple spin-echo and conventional spin-echo diffusion weighting were examined to demonstrate the efficacy of multiple spin-echo diffusion sequence to improve image quality and throughput. Effects of signal averaging using complex, magnitude and phased images from multiple spin-echo diffusion weighting were also assessed. Bayesian probability theory was used to generate phased images by moving the coherent signals to the real channel to eliminate the effect of phase variation between echoes while preserving the Gaussian noise distribution. Signal averaging of phased multiple spin-echo images potentially solves both the phase incoherence problem and the bias of the elevated Rician noise distribution in magnitude image. The proposed signal averaging with Bayesian phase-aligned multiple spin-echo images approach was compared to the conventional spin-echo data acquired with doubling the scan time. The diffusion tensor imaging parameters were compared in the mouse contusion spinal cord injury. Significance level (p-value) and effect size (Cohen's d) were reported between the control and contused spinal cord to inspect the sensitivity of each approach in detecting white matter pathology.
  
  
  RESULTS
  Compared to the spin-echo image, the signal-noise-ratio increased to 1.84-fold using the phased image averaging and to 1.30-fold using magnitude image averaging in the spinal cord white matter. Multiple spin-echo phased image averaging showed improved image quality of the mouse spinal cord among the tested methods. Diffusion tensor imaging metrics obtained from multiple spin-echo phased images using three echoes and two averages closely agreed with those derived by spin-echo magnitude data with four averages (two times more in acquisition time). The phased image averaging correctly reflected pathological features in contusion spinal cord injury.
  
  
  CONCLUSIONS
  Our in vivo imaging results indicate that averaging the phased multiple spin-echo images yields an 84% signal-noise-ratio increase over the spin-echo images and a 41% gain over the magnitude averaged multiple spin-echo images with equal acquisition time. Current results from the animal model of spinal cord injury suggest that the phased multiple spin-echo images could be used to improve signal-noise-ratio.
authors.affiliation: Radiology & Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Tsang-Wei
authors.initials: TW
authors.lastname: Tu
authors.affiliation: Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Budde
authors.affiliation: Department of Pathology and Immunology, Washington University, St. Louis, MO, USA.
authors.forename: Mingqiang
authors.initials: M
authors.lastname: Xie
authors.affiliation: Department of Chemistry, Washington University, St. Louis, MO, USA.
authors.forename: Ying-Jr
authors.initials: YJ
authors.lastname: Chen
authors.affiliation: Department of Radiology, Washington University, St. Louis, MO, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Pathology and Immunology, Washington University, St. Louis, MO, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Quirk
authors.affiliation: Department of Radiology, Washington University, St. Louis, MO, USA. Electronic address: ssong@wustl.edu.
authors.forename: Sheng-Kwei
authors.initials: SK
authors.lastname: Song
mesh_terms: D000818:Animals; D016477:Artifacts; D001499:Bayes Theorem; D056324:Diffusion Tensor Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D007091:Image Processing, Computer-Assisted / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D016011:Normal Distribution; D011336:Probability; D059629:Signal-To-Noise Ratio; D013116:Spinal Cord / Q000473:pathology*; D013119:Spinal Cord Injuries / Q000473:pathology
keywords: Bayesian phasing analysis; DTI; Multiple spin-echo; Spinal cord
references.citation: J Neurotrauma. 2000 Apr;17(4):299-319
references.pmid: 10776914
references.citation: Magn Reson Imaging. 1998 Oct;16(8):877-86
references.pmid: 9814769
references.citation: J Magn Reson. 2008 Apr;191(2):184-92
references.pmid: 18191597
references.citation: Med Phys. 1985 Mar-Apr;12(2):232-3
references.pmid: 4000083
references.citation: Magn Reson Med. 1995 Dec;34(6):910-4
references.pmid: 8598820
references.citation: J Magn Reson Imaging. 2005 Aug;22(2):307-10
references.pmid: 16028249
references.citation: J Magn Reson. 2007 Aug;187(2):293-305
references.pmid: 17572124
references.citation: Magn Reson Med. 1986 Jun;3(3):397-417
references.pmid: 3724419
references.citation: Neuroimage. 2013 Jan 15;65:209-15
references.pmid: 23085108
references.citation: Magn Reson Med. 1986 Aug;3(4):562-74
references.pmid: 3747818
references.citation: Neurobiol Dis. 2006 Mar;21(3):626-32
references.pmid: 16298135
references.citation: Magn Reson Med. 1993 Aug;30(2):201-6
references.pmid: 8366801
references.citation: Magn Reson Med. 1999 Aug;42(2):300-6
references.pmid: 10440955
references.citation: Radiology. 1990 Nov;177(2):407-14
references.pmid: 2217777
references.citation: J Magn Reson. 2002 Apr;155(2):278-92
references.pmid: 12036339
references.citation: J Magn Reson. 2008 Apr;191(2):193-201
references.pmid: 18187351
references.citation: AJNR Am J Neuroradiol. 2011 Aug;32(7):1188-94
references.pmid: 21700789
references.citation: Magn Reson Med. 2002 Jul;48(1):6-14
references.pmid: 12111926
references.citation: J Neurotrauma. 2009 Aug;26(8):1395-404
references.pmid: 19257804
references.citation: NMR Biomed. 2014 Apr;27(4):390-8
references.pmid: 24436112
references.citation: J Magn Reson. 2005 Dec;177(2):329-35
references.pmid: 16185903
references.citation: Neuroimage. 2003 Nov;20(3):1714-22
references.pmid: 14642481
references.citation: Neuroimage. 2013 Nov 15;82:574-85
references.pmid: 23770410
references.citation: Magn Reson Med. 2008 Dec;60(6):1512-7
references.pmid: 19025894
references.citation: Magn Reson Med. 2010 Apr;63(4):1125-34
references.pmid: 20373416
references.citation: Invest Ophthalmol Vis Sci. 2012 Jan 17;53(1):136-42
references.pmid: 22159023
references.citation: Magn Reson Med. 1995 Jul;34(1):65-73
references.pmid: 7674900
references.citation: J Magn Reson. 2009 May;198(1):49-56
references.pmid: 19181549
references.citation: Neurobiol Dis. 2004 Apr;15(3):640-7
references.pmid: 15056472
references.citation: Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:2715-8
references.pmid: 19964039
references.citation: Magn Reson Med. 1997 Mar;37(3):336-40
references.pmid: 9055221
references.citation: IEEE Trans Med Imaging. 1991;10(1):53-65
references.pmid: 18222800
references.citation: Magn Reson Med. 1992 Sep;27(1):142-64
references.pmid: 1435200
references.citation: Magn Reson Med. 1997 Dec;38(6):868-73
references.pmid: 9402185
references.citation: Magn Reson Med. 1986 Dec;3(6):823-33
references.pmid: 3821461
references.citation: Magn Reson Med. 2007 Apr;57(4):688-95
references.pmid: 17390365
references.citation: Nat Protoc. 2013 Feb;8(2):409-17
references.pmid: 23424749
references.citation: Magn Reson Med. 1997 Nov;38(5):852-7
references.pmid: 9358462
references.citation: Magn Reson Med. 1996 Aug;36(2):287-93
references.pmid: 8843383
references.citation: NMR Biomed. 2008 Oct;21(8):868-77
references.pmid: 18574855
references.citation: J Neurosci. 2007 Oct 31;27(44):11869-76
references.pmid: 17978027
references.citation: Magn Reson Med. 1986 Oct;3(5):707-21
references.pmid: 3784888
references.citation: J Neurosci Res. 2006 Apr;83(5):801-10
references.pmid: 16456864
references.citation: NMR Biomed. 2013 Nov;26(11):1484-95
references.pmid: 23775778
references.citation: Phys Med Biol. 1999 Dec;44(12):N261-4
references.pmid: 10616158
references.citation: Magn Reson Med. 2003 Aug;50(2):343-53
references.pmid: 12876711
references.citation: Med Image Comput Comput Assist Interv. 2006;9(Pt 1):117-25
references.pmid: 17354881
references.citation: J Neurosci. 2009 Mar 4;29(9):2805-13
references.pmid: 19261876
references.citation: Psychol Bull. 1992 Jul;112(1):155-9
references.pmid: 19565683
references.citation: J Neurotrauma. 2010 Jan;27(1):253-62
references.pmid: 19715399
references.citation: Magn Reson Med. 2002 Jan;47(1):42-52
references.pmid: 11754441