title: Maximizing MR signal for 2D UTE slice selection in the presence of rapid transverse relaxation.
abstract: Ultrashort TE (UTE) sequences allow direct visualization of tissues with very short T2 relaxation times, such as tendons, ligaments, menisci, and cortical bone. In this work, theoretical calculations, simulations, and phantom studies, as well as in vivo imaging were performed to maximize signal-to-noise ratio (SNR) for slice selective RF excitation for 2D UTE sequences. The theoretical calculations and simulations were based on the Bloch equations, which lead to analytic expressions for the optimal RF pulse duration and amplitude to maximize magnetic resonance signal in the presence of rapid transverse relaxation. In steady state, it was found that the maximum signal amplitude was not obtained at the classical Ernst angle, but at an either lower or higher flip angle, depending on whether the RF pulse duration or amplitude was varied, respectively.
authors.affiliation: GE Healthcare, University of California, San Francisco. Electronic address: Michael.carl@ge.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Carl
authors.affiliation: Radiology Department, University of California, San Francisco.
authors.forename: Jing-Tzyh Alan
authors.initials: JT
authors.lastname: Chiang
authors.affiliation: Radiology Department, University of California, San Diego.
authors.forename: Jiang
authors.initials: J
authors.lastname: Du
mesh_terms: D001842:Bone and Bones / Q000473:pathology*; D003198:Computer Simulation; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007717:Knee / Q000473:pathology*; D008022:Ligaments / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008670:Metals / Q000737:chemistry; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D019047:Phantoms, Imaging; D019736:Prostheses and Implants; D059629:Signal-To-Noise Ratio; D013710:Tendons / Q000473:pathology*; D013977:Tibia / Q000473:pathology
chemical_list: D008670:Metals
keywords: 2D UTE; Ernst Angle; RF Optimization; Short T(2)