title: Accelerated fractional ventilation imaging with hyperpolarized Gas MRI.
abstract: OBJECTIVE
  To investigate the utility of accelerated imaging to enhance multibreath fractional ventilation (r) measurement accuracy using hyperpolarized gas MRI. Undersampling shortens the breath-hold time, thereby reducing the O2 -induced signal decay and allows subjects to maintain a more physiologically relevant breathing pattern. Additionally, it may improve r estimation accuracy by reducing radiofrequency destruction of hyperpolarized gas.
  
  
  METHODS
  Image acceleration was achieved using an eight-channel phased array coil. Undersampled image acquisition was simulated in a series of ventilation images and data was reconstructed for various matrix sizes (48-128) using generalized auto-calibrating partially parallel acquisition. Parallel accelerated r imaging was also performed on five mechanically ventilated pigs.
  
  
  RESULTS
  Optimal acceleration factor was fairly invariable (2.0-2.2×) over the range of simulated resolutions. Estimation accuracy progressively improved with higher resolutions (39-51% error reduction). In vivo r values were not significantly different between the two methods: 0.27 ± 0.09, 0.35 ± 0.06, 0.40 ± 0.04 (standard) versus 0.23 ± 0.05, 0.34 ± 0.03, 0.37 ± 0.02 (accelerated); for anterior, medial, and posterior slices, respectively, whereas the corresponding vertical r gradients were significant (P < 0.001): 0.021 ± 0.007 (standard) versus 0.019 ± 0.005 (accelerated) (cm(-1) ).
  
  
  CONCLUSIONS
  Quadruple phased array coil simulations resulted in an optimal acceleration factor of ∼2× independent of imaging resolution. Results advocate undersampled image acceleration to improve accuracy of fractional ventilation measurement with hyperpolarized gas MRI.
authors: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors: Kiarash
authors: K
authors: Emami
authors: Yinan
authors: Y
authors: Xu
authors: Hooman
authors: H
authors: Hamedani
authors: Harrilla
authors: H
authors: Profka
authors: Stephen
authors: S
authors: Kadlecek
authors: Yi
authors: Y
authors: Xin
authors: Masaru
authors: M
authors: Ishii
authors: Rahim R
authors: RR
authors: Rizi
mesh_terms: D000465:Algorithms; D000818:Animals; D006371:Helium; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D012123:Pulmonary Ventilation / Q000502:physiology*; D011868:Radioisotopes; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine
chemical_list: D011868:Radioisotopes; D006371:Helium
keywords: accelerated ventilation imaging; fractional ventilation; generalized auto-calibrating partially parallel acquisition; hyperpolarized gas MRI; mechanical ventilation; parallel MRI; pulmonary ventilation; quantitative lung imaging
references: Chest. 1985 Mar;87(3):359-62
references: 3971762
references: J Appl Physiol. 1974 Jul;37(1):8-17
references: 4836560
references: Med Image Anal. 2008 Dec;12(6):752-63
references: 18501665
references: J Appl Physiol (1985). 2002 Nov;93(5):1841-51
references: 12381773
references: Acad Radiol. 2004 Jul;11(7):729-34
references: 15217589
references: Magn Reson Med. 2010 Jan;63(1):137-50
references: 19877277
references: Magn Reson Med. 2002 Jun;47(6):1202-10
references: 12111967
references: Acad Radiol. 2005 Nov;12(11):1414-22
references: 16253853
references: NMR Biomed. 2012 Sep;25(9):1015-25
references: 22290603
references: J Appl Physiol. 1960 May;15:405-10
references: 13844133
references: Phys Rev A. 1995 Jul;52(1):862-865
references: 9912313
references: J Appl Physiol (1985). 1995 Feb;78(2):597-607
references: 7759429
references: J Appl Physiol (1985). 2001 Feb;90(2):421-30
references: 11160037
references: Radiology. 2011 Oct;261(1):283-92
references: 21813741
references: Magn Reson Med. 1995 Dec;34(6):910-4
references: 8598820
references: J Appl Physiol Respir Environ Exerc Physiol. 1978 Mar;44(3):416-23
references: 632182
references: Radiology. 2010 Sep;256(3):985-97
references: 20651060
references: Magn Reson Med. 2005 May;53(5):1055-64
references: 15844148
references: J Appl Physiol (1985). 2007 Jan;102(1):468-76
references: 16990505
references: J Nucl Med. 1996 May;37(5):807-14
references: 8965150
references: J Appl Physiol. 1966 May;21(3):749-59
references: 5912744
references: Magn Reson Med. 2006 May;55(5):1132-41
references: 16586457
references: J Appl Physiol (1985). 2010 Dec;109(6):1950-9
references: 20930129
references: Magn Reson Med. 2002 Aug;48(2):223-32
references: 12210930
references: Acad Radiol. 2009 Jun;16(6):718-25
references: 19268611
references: J Clin Invest. 1962 Mar;41:519-31
references: 13864417
references: J Appl Physiol. 1966 May;21(3):767-77
references: 5912746
references: Magn Reson Med. 2003 Oct;50(4):777-83
references: 14523964
references: J Appl Physiol. 1964 May;19:395-402
references: 14173534