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Susceptibility effects in hyperpolarized 3 He lung MRI at 1.5T and 3T
Author(s) -
Deppe Martin H.,
ParraRobles Juan,
Ajraoui Salma,
Parnell Steven R.,
Clemence Matthew,
Schulte Rolf F.,
Wild Jim M.
Publication year - 2009
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21852
Subject(s) - nuclear magnetic resonance , voxel , nuclear medicine , attenuation , subpixel rendering , quantitative susceptibility mapping , magnetic resonance imaging , materials science , chemistry , medicine , physics , radiology , optics , pixel
Purpose To compare susceptibility effects in hyperpolarized 3 He lung MRI at the clinically relevant field strengths of 1.5T and 3T. Materials and Methods Susceptibility‐related B 0 inhomogeneity was evaluated on a macroscopic scale by B 0 field mapping via phase difference. Subpixel susceptibility effects were quantified by mapping T * 2 . Comparison was made between ventilation images obtained from the same volunteers at both field strengths. Results The B 0 maps at 3T show enhanced off‐resonance effects close to the diaphragm and the ribs due to susceptibility differences. The average T * 2from a voxel (20 × 4 × 4) mm 3 was determined as T * 2= 27.8 msec ± 1.2 msec at 1.5T compared to T * 2= 14.4 msec ± 2.6 msec at 3T. In ventilation images the most prominent effect is increased signal attenuation close to the intrapulmonary blood vessels at higher B 0 . Conclusion Image homogeneity and T * 2are lower at 3T due to increased B 0 inhomogeneity as a consequence of susceptibility differences. These findings indicate that 3 He imaging at 3T has no obvious benefit over imaging at 1.5T, as signal‐to‐noise ratio (SNR) was comparable for both fields in this work. J. Magn. Reson. Imaging 2009;30:418–423. © 2009 Wiley‐Liss, Inc.