Adiabatic RF pulse design for Bloch‐Siegert B+ mapping. Issue 3 (5th October 2012)

• Record Type: Journal Article
• Authors: Khalighi, Mohammad Mehdi; Rutt, Brian K.; Kerr, Adam B.
• Is Part Of: Magnetic resonance in medicine. Volume 70:Issue 3(2013:Sep.)
• Page Start: 829
• Page End: 835
• Publication Date: 2012-10-05
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.24507
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The Bloch–Siegert (B–S) <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg2xbk9c2t" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:07403194:media:mrm24507:mrm24507-math-0003" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>B</mml:mi><mml:mn>1</mml:mn><mml:mi>+</mml:mi></mml:msubsup></mml:math></alternatives> mapping method has been shown to be fast and accurate, yet it suffers from high Specific Absorption Rate (SAR) and moderately long echo time. An adiabatic RF pulse design is introduced here for optimizing the off‐resonant B–S RF pulse to achieve more B–S <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg2xbk9c18" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:07403194:media:mrm24507:mrm24507-math-0004" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>B</mml:mi><mml:mn>1</mml:mn><mml:mi>+</mml:mi></mml:msubsup></mml:math></alternatives> measurement sensitivity for a given pulse width. The extra sensitivity can be used for higher angle‐to‐noise ratio <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg2xbk9c0q" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:07403194:media:mrm24507:mrm24507-math-0005" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>B</mml:mi><mml:mn>1</mml:mn><mml:mi>+</mml:mi></mml:msubsup></mml:math></alternatives> maps or traded off for faster scans. Using numerical simulations and phantom experiments, it is shown that a numerically optimized 2‐ms adiabatic B‐S pulse is 2.5 times more efficient than a conventional 6‐ms Fermi‐shaped B–S pulse. The adiabatic B–S pulse performance is validated in a phantom, and in vivo brain <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg2xbk9bx3" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:07403194:media:mrm24507:mrm24507-math-0006" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>B</mml:mi><mml:mn>1</mml:mn><mml:mi>+</mml:mi></mml:msubsup></mml:math></alternatives> mapping at 3T and 7T are shown. Magn Reson Med 70:829–835, 2013. © 2012 Wiley Periodicals, Inc.</p> </abstract>