title: On the suppression of background signals originating from NMR hardware components. Application to zero echo time imaging and relaxation time analysis.
abstract: Modern NMR imaging systems used for biomedical research are equipped with B0 gradient systems with strong maximum gradient strength and short switching time enabling (1)H NMR measurements of samples with very short transverse relaxation times. However, background signal originating from non-optimized RF coils may hamper experiments with ultrashort delays between RF excitation and signal reception. We demonstrate that two simple means, outer volume suppression and the use of shaped B0 fields produced by higher-order shim coils, allow a considerable suppression of disturbing background signals. Thus, the quality of NMR images acquired at ultrashort or zero echo time is improved and systematic errors in quantitative data evaluation are avoided. Fields of application comprise MRI with ultrashort echo time or relaxation time analysis, for both biomedical research and characterizing porous media filled with liquids or gases.
authors.affiliation: University of Bremen, Department Chemistry, in-vivo-MR group, Bremen, Germany. Electronic address: wdreher@uni-bremen.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dreher
authors.affiliation: University of Bremen, Department Chemistry, Institute of Applied and Physical Chemistry, Bremen, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Bardenhagen
authors.affiliation: University of Bremen, Department Chemistry, in-vivo-MR group, Bremen, Germany.
authors.forename: Li
authors.initials: L
authors.lastname: Huang
authors.affiliation: University of Bremen, Department Chemistry, Institute of Applied and Physical Chemistry, Bremen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Bäumer
mesh_terms: D002244:Carbon / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004867:Equipment Design; D005740:Gases; D005782:Gels; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D010363:Pattern Recognition, Automated; D016062:Porosity; D012815:Signal Processing, Computer-Assisted; D014867:Water / Q000737:chemistry
chemical_list: D005740:Gases; D005782:Gels; D014867:Water; D002244:Carbon; D004121:Dimethyl Sulfoxide
keywords: Higher-order shim coils; Outer volume suppression (OVS); Porous media; Relaxation time analysis; T(1) relaxation; Zero echo time (ZTE)