Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

PURPOSE: Phosphorus ((31)P) MR spectroscopic imaging (MRSI) is primarily applied with sensitive, surface radiofrequency (RF) coils that provide inhomogeneous excitation RF field (B1(+)) and rough localization due to their B1(+) and sensitivity (B1(-)) profiles. A careful and time-consuming pulse adjustment and an accurate knowledge of flip angle (FA) are mandatory for quantification corrections. MATERIALS AND METHODS: In this study, a simple, fast, and universal (31)P B1(+) mapping method is proposed, which requires fast steady-state MRSI (typically one sixth of normal measurement time) in addition to the typical MRSI acquired within the examination protocol. The FA maps are calculated from the ratio of the signal intensities acquired by these two measurements and were used to correct for the influence of B1(+) on the metabolite maps. RESULTS: In vitro tests were performed on two scanners (3 and 7 Tesla) using a surface and a volume coil. The calculated FA maps were in good agreement with adjusted nominal FAs and the theoretical calculation using the Biot-Savart law. The method was successfully tested in vivo in the calf muscle and the brain of healthy volunteers (n = 4). The corrected metabolite maps show higher homogeneity compared with their noncorrected versions. CONCLUSION: The calculated FA maps helped with B1(+) inhomogeneity corrections of acquired in vivo data, and should also be useful with optimization and testing of pulse performances, or with the construction quality tests of new dual-channel (1)H/(31)P coils.

Original publication

DOI

10.1002/jmri.24401

Type

Journal article

Journal

J Magn Reson Imaging

Publication Date

08/2014

Volume

40

Pages

391 - 397

Keywords

31P, 7 Tesla, B1 mapping, MRSI, flip-angle, steady-state, Adult, Brain, Equipment Design, Equipment Failure Analysis, Feasibility Studies, Female, Humans, Image Enhancement, Image Interpretation, Computer-Assisted, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Male, Molecular Imaging, Phosphorus Compounds, Phosphorus Isotopes, Reproducibility of Results, Sensitivity and Specificity