title: Two-pulse biexponential-weighted 23Na imaging.
abstract: A new method is proposed for acquiring 3D biexponential-weighted sodium images with two instead of three RF pulses to allow for shorter repetition time at high magnetic fields (B0≥7 T) and reduced SAR. The second pulse converts single- into triple-quantum coherences in regions containing sodium ions which are restricted in mobility. Since only single-quantum coherences can be detected, an image acquired after the second pulse is intrinsically single-quantum-filtered and can be used to generate a biexponential-weighted sodium image by a weighted subtraction with the spin-density-weighted image acquired between the pulses. The proposed sequence generates biexponential-weighted sodium images of in vivo human brain with 140% higher SNR than triple-quantum-filtered sodium images and 4% higher SNR than a biexponential-weighted sequence with three RF pulses at equal acquisition time and with 1/3 lower SAR. As SAR is reduced, accordingly repetition time can be spared to obtain even higher SNR-time efficiency. In comparison to a difference image generated from two images of a double-readout sequence, the proposed two-pulse sequence yields about 14% higher SNR. Our new two-pulse biexponential-weighted sequence allows for acquisition of full 3D data sets of the human brain in vivo with a nominal resolution of (5 mm)(3) in about 10 min.
authors: German Cancer Research Center (DKFZ), Department of Medical Physics in Radiology, Heidelberg, Germany.
authors: Nadia
authors: N
authors: Benkhedah
authors: German Cancer Research Center (DKFZ), Department of Medical Physics in Radiology, Heidelberg, Germany.
authors: Peter
authors: P
authors: Bachert
authors: German Cancer Research Center (DKFZ), Department of Medical Physics in Radiology, Heidelberg, Germany. Electronic address: a.nagel@dkfz.de.
authors: Armin M
authors: AM
authors: Nagel
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology; D004574:Electromagnetic Fields; D006801:Humans; D007089:Image Enhancement; D007090:Image Interpretation, Computer-Assisted; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011522:Protons; D059629:Signal-To-Noise Ratio; D012964:Sodium / Q000737:chemistry*; D012975:Sodium Isotopes; D051598:Whole Body Imaging
chemical_list: D011522:Protons; D012975:Sodium Isotopes; D012964:Sodium
keywords: Multiple-quantum filter; Sodium MRI; Triple-quantum filter