Susceptibility effects in hyperpolarized (3)He lung MRI at 1.5T and 3T.
OBJECTIVE
To compare susceptibility effects in hyperpolarized (3)He lung MRI at the clinically relevant field strengths of 1.5T and 3T.


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 T2. 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 T2 from a voxel (20 x 4 x 4) mm(3) was determined as T2 = 27.8 msec +/- 1.2 msec at 1.5T compared to T2 = 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).


CONCLUSIONS
Image homogeneity and T2 are 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.
Deppe
Martin H
MH
Academic Radiology, University of Sheffield, Royal Hallamshire Hospital, Sheffield, UK.
Parra-Robles
Juan
J
Ajraoui
Salma
S
Parnell
Steven R
SR
Clemence
Matthew
M
Schulte
Rolf F
RF
Wild
Jim M
JM
D000328:Adult; D003287:Contrast Media; D006371:Helium; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male
D003287:Contrast Media; D006371:Helium