Phase‐contrast velocity mapping for highly diffusive fluids: Optimal bipolar gradient pulse parameters for hyperpolarized helium‐3. Issue 4 (11th November 2013)

• Record Type: Journal Article
• Authors: Martin, Lionel; Maître, Xavier; de Rochefort, Ludovic; Sarracanie, Mathieu; Friese, Marlies; Hagot, Pascal; Durand, Emmanuel
• Is Part Of: Magnetic resonance in medicine. Volume 72:Issue 4(2014:Oct.)
• Page Start: 1072
• Page End: 1078
• Publication Date: 2013-11-11
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.25005
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="mrm25005-sec-0001" sec-type="section"> <title>Purpose</title> <p>In MR‐velocity phase‐contrast measurements, increasing the encoding bipolar gradient, i.e., decreasing the field of speed, usually improves measurement precision. However, in gases, fast diffusion during the bipolar gradient pulses may dramatically decrease the signal‐to‐noise ratio, thus degrading measurement precision. These two effects are contradictory. This work aims at determining the optimal sequence parameters to improve the velocity measurement precision.</p> </sec> <sec id="mrm25005-sec-0002" sec-type="section"> <title>Theory and Methods</title> <p>This work presents the theoretical optimization of bipolar gradient parameters (duration and amplitude) to improve velocity measurement precision. An analytical approximation is given as well as a numerical optimization. It is shown that the solution depends on the diffusion coefficient and T<sub>2</sub>*. Experimental validation using hyperpolarized <sup>3</sup>He diluted in various buffer gases (<sup>4</sup>He, N<sub>2</sub>, and SF<sub>6</sub>) is presented at 1.5 Tesla (T) in a straight pipe.</p> </sec> <sec id="mrm25005-sec-0003" sec-type="section"> <title>Results</title> <p>Excellent agreement was found with the theoretical results for prediction of optimal field of speed and good agreement was found for the precision in measured velocity, but for SF<sub>6</sub> buffered gas.</p> </sec> <sec id="mrm25005-sec-0004" sec-type="section"> <title>Conclusion</title> <p>The theoretical predictions were validated, providing a way to optimize velocity mapping in gases. Magn Reson Med 72:1072–1078, 2014. © 2013 Wiley Periodicals, Inc.</p> </sec> </abstract>