Optimization of rapid acquisition with relaxation enhancement (RARE) pulse sequence parameters for 19F‐MRI studies. Issue 1 (13th November 2013)

• Record Type: Journal Article
• Authors: Mastropietro, Alfonso; De Bernardi, Elisabetta; Breschi, Gian Luca; Zucca, Ileana; Cametti, Massimo; Soffientini, Chiara Dolores; de Curtis, Marco; Terraneo, Giancarlo; Metrangolo, Pierangelo; Spreafico, Roberto; Resnati, Giuseppe; Baselli, Giuseppe
• Is Part Of: Journal of magnetic resonance imaging. Volume 40:Issue 1(2014)
• Page Start: 162
• Page End: 170
• Publication Date: 2013-11-13
• Subjects: Magnetic resonance imaging -- Periodicals; 616
• DOI: 10.1002/jmri.24347
• Languages: English
• ISSNs: 1053-1807

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="jmri24347-sec-0001" sec-type="section"> <title>Purpose</title> <p>To optimize signal‐to‐noise ratio (SNR) in fast spin echo (rapid acquisition with relaxation enhancement [RARE]) sequences and to improve sensitivity in <sup>19</sup>F magnetic resonance imaging (MRI) on a 7T preclinical MRI system, based on a previous experimental evaluation of T<sub>1</sub> and T<sub>2</sub> actual relaxation times.</p> </sec> <sec id="jmri24347-sec-0002" sec-type="section"> <title>Materials and Methods</title> <p>Relative SNR changes were theoretically calculated at given relaxation times (T<sub>1</sub>, T<sub>2</sub>) and mapped in RARE parameter space (TR, number of echoes, flip back pulse), at fixed acquisition times. T<sub>1</sub> and T<sub>2</sub> of KPF<sub>6</sub> 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.</p> </sec> <sec id="jmri24347-sec-0003" sec-type="section"> <title>Results</title> <p>The optimized setting largely depended on T<sub>1</sub>, T<sub>2</sub> times and the use of flip back pulse improved SNR up to 30% in case of low T<sub>1</sub>/T<sub>2</sub> ratios. Relaxation times in different conditions showed negligible changes in T<sub>1</sub> (below 14%) and more evident changes in T<sub>2</sub> (−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 × 10<sup>16</sup> fluorine atoms per voxel.</p> </sec> <sec id="jmri24347-sec-0004" sec-type="section"> <title>Conclusion</title> <p>Optimal settings according to measured relaxation times can significantly improve the sensitivity threshold in <sup>19</sup>F MRI studies. They were provided in a wide range of (T<sub>1</sub>, T<sub>2</sub>) values and experimentally validated showing good agreement. <bold>J. Magn. Reson. Imaging 2014;40:162–170</bold>. © <bold>2013 Wiley Periodicals, Inc</bold>.</p> </sec> </abstract>