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Optimization of steady‐state free precession MRI for lung ventilation imaging with 19 F C 3 F 8 at 1.5T and 3T
Author(s) -
Maunder Adam,
Rao Madhwesha,
Robb Fraser,
Wild Jim M.
Publication year - 2019
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27479
Subject(s) - steady state free precession imaging , in vivo , imaging phantom , nuclear magnetic resonance , nuclear medicine , magnetic resonance imaging , gradient echo , ventilation (architecture) , steady state (chemistry) , relaxation (psychology) , biomedical engineering , materials science , physics , chemistry , medicine , radiology , biology , microbiology and biotechnology , thermodynamics
Purpose: To optimize 19 F imaging pulse sequences for perfluoropropane (C 3 F 8 ) gas human lung ventilation MRI considering intrinsic in vivo relaxation parameters at both 1.5T and 3T. Methods: Optimization of the imaging parameters for both 3D spoiled gradient (SPGR) and steady‐state free precession (SSFP) 19 F imaging sequences with inhaled 79% C 3 F 8% and 21% oxygen was performed. Phantom measurements were used to validate simulations of SNR. In vivo parameter mapping and sequence optimization and comparison was performed by imaging the lungs of a healthy adult volunteer. T 1 and T 2 * mapping was performed in vivo to optimize sequence parameters for in vivo lung MRI. The performance of SSFP and SPGR was then evaluated in vivo at 1.5T and 3T. Results: The in vivo T 2 * of C 3 F 8 was shown to be dependent upon lung inflation level (2.04 ms ± 36% for residual volume and 3.14 ms ± 28% for total lung capacity measured at 3T), with lower T 2 * observed near the susceptibility interfaces of the diaphragm and around pulmonary blood vessels. Simulation and phantom measurements indicate that a factor of ~2‐3 higher SNR can be achieved with SSFP when compared with optimized SPGR. In vivo lung imaging showed a 1.7 factor of improvement in SNR achieved at 1.5T, while the theoretical improvement at 3T was not attained due to experimental SAR constraints, shorter in vivo T 1 , and B 0 inhomogeneity. Conclusion: SSFP imaging provides increased SNR in lung ventilation imaging of C 3 F 8 demonstrated at 1.5T with optimized SSFP similar to the SNR that can be obtained at 3T with optimized SPGR.