Flip angle–optimized fast dynamic T1 mapping with a 3D gradient echo sequence. Issue 3 (17th March 2014)

• Record Type: Journal Article
• Authors: Dietrich, Olaf; Freiermuth, Maximilian; Willerding, Linus; Reiser, Maximilian F.; Peller, Michael
• Is Part Of: Magnetic resonance in medicine. Volume 73:Issue 3(2015:Mar.)
• Page Start: 1158
• Page End: 1163
• Publication Date: 2014-03-17
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.25199
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="mrm25199-sec-0001" sec-type="section"> <title>Purpose</title> <p>To analyze the flip angle dependence and to optimize the statistical precision of a fast three‐dimensional (3D) <italic>T</italic><sub>1</sub> mapping technique based on the variable flip angle (VFA) method. The proposed single flip angle (1FA) approach acquires only a single 3D spoiled gradient echo data set for each time point of the dynamical series in combination with a longer baseline measurement.</p> </sec> <sec id="mrm25199-sec-0002" sec-type="section"> <title>Theory and Methods</title> <p>The optimal flip angle for the dynamic series can be calculated as <italic>α</italic><sub>dyn, opt</sub> = arccos[(2<italic>E</italic><sub>1</sub> − 1)/(2 − <italic>E</italic><sub>1</sub>)] (with <italic>E</italic><sub>1</sub> = exp(−<italic>T</italic><sub>R</sub>/<italic>T</italic><sub>1</sub>)) by minimizing the statistical error of <italic>T</italic><sub>1</sub>. <italic>T</italic><sub>1</sub> maps of a liquid phantom with step‐wise increasing concentrations of contrast agent were measured using a saturation recovery (SR) and a VFA/1FA technique with 11 flip angles. The standard deviation of the parameter maps was defined as statistical error of the 1FA measurement.</p> </sec> <sec id="mrm25199-sec-0003" sec-type="section"> <title>Results</title> <p>The measured statistical error of the 1FA technique as a function of <italic>α</italic><sub>dyn</sub> agrees with the derived theoretical curve. The optimal flip angle increases from about 5° for <italic>T</italic><sub>1</sub> = 2629 ms to 30° for <italic>T</italic><sub>1</sub> = 137 ms. The relative deviation between 1FA and SR measurements varies between −2.9 % and +10.3 %. Measurements in vivo confirm the expression for the optimal flip angle.</p> </sec> <sec id="mrm25199-sec-0004" sec-type="section"> <title>Conclusion</title> <p>The proposed flip angle–optimized 1FA technique optimizes the precision of <italic>T</italic><sub>1</sub> values in dynamic phantom measurements. <bold>Magn Reson Med 73:1158–1163, 2015. © 2014 Wiley Periodicals, Inc.</bold></p> </sec> </abstract>