TY - JOUR
T1 - Optimization of rapid acquisition with relaxation enhancement (RARE) pulse sequence parameters for 19F-MRI studies
AU - Mastropietro, Alfonso
AU - De Bernardi, Elisabetta
AU - Breschi, Gian Luca
AU - Zucca, Ileana
AU - Cametti, Massimo
AU - Soffientini, Chiara Dolores
AU - De Curtis, Marco
AU - Terraneo, Giancarlo
AU - Metrangolo, Pierangelo
AU - Spreafico, Roberto
AU - Resnati, Giuseppe
AU - Baselli, Giuseppe
PY - 2014
Y1 - 2014
N2 - Purpose To optimize signal-to-noise ratio (SNR) in fast spin echo (rapid acquisition with relaxation enhancement [RARE]) sequences and to improve sensitivity in 19F magnetic resonance imaging (MRI) on a 7T preclinical MRI system, based on a previous experimental evaluation of T 1 and T2 actual relaxation times. Materials and Methods Relative SNR changes were theoretically calculated at given relaxation times (T1, T2) and mapped in RARE parameter space (TR, number of echoes, flip back pulse), at fixed acquisition times. T1 and T 2 of KPF6 phantom samples (solution, agar mixtures, ex vivo perfused brain) were measured and experimental SNR values were compared with simulations, at optimal and suboptimal RARE parameter values. Results The optimized setting largely depended on T1, T2 times and the use of flip back pulse improved SNR up to 30% in case of low T 1/T2 ratios. Relaxation times in different conditions showed negligible changes in T1 (below 14%) and more evident changes in T2 (-95% from water solution to ex vivo brain). Experimental data confirmed theoretical forecasts, within an error margin always below 4.1% at SNR losses of ∼20% and below 8.8% at SNR losses of ∼40%. The optimized settings permitted a detection threshold at a concentration of 0.5 mM, corresponding to 6.22 × 1016 fluorine atoms per voxel. Conclusion Optimal settings according to measured relaxation times can significantly improve the sensitivity threshold in 19F MRI studies. They were provided in a wide range of (T1, T2) values and experimentally validated showing good agreement.
AB - Purpose To optimize signal-to-noise ratio (SNR) in fast spin echo (rapid acquisition with relaxation enhancement [RARE]) sequences and to improve sensitivity in 19F magnetic resonance imaging (MRI) on a 7T preclinical MRI system, based on a previous experimental evaluation of T 1 and T2 actual relaxation times. Materials and Methods Relative SNR changes were theoretically calculated at given relaxation times (T1, T2) and mapped in RARE parameter space (TR, number of echoes, flip back pulse), at fixed acquisition times. T1 and T 2 of KPF6 phantom samples (solution, agar mixtures, ex vivo perfused brain) were measured and experimental SNR values were compared with simulations, at optimal and suboptimal RARE parameter values. Results The optimized setting largely depended on T1, T2 times and the use of flip back pulse improved SNR up to 30% in case of low T 1/T2 ratios. Relaxation times in different conditions showed negligible changes in T1 (below 14%) and more evident changes in T2 (-95% from water solution to ex vivo brain). Experimental data confirmed theoretical forecasts, within an error margin always below 4.1% at SNR losses of ∼20% and below 8.8% at SNR losses of ∼40%. The optimized settings permitted a detection threshold at a concentration of 0.5 mM, corresponding to 6.22 × 1016 fluorine atoms per voxel. Conclusion Optimal settings according to measured relaxation times can significantly improve the sensitivity threshold in 19F MRI studies. They were provided in a wide range of (T1, T2) values and experimentally validated showing good agreement.
KW - fast spin echo
KW - molecular imaging
KW - pulse sequence optimization
KW - RARE
KW - sensitivity threshold
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U2 - 10.1002/jmri.24347
DO - 10.1002/jmri.24347
M3 - Article
C2 - 25050436
AN - SCOPUS:84902374270
SN - 1053-1807
VL - 40
SP - 162
EP - 170
JO - Journal of Magnetic Resonance Imaging
JF - Journal of Magnetic Resonance Imaging
IS - 1
ER -