title: An eight-channel T/R head coil for parallel transmit MRI at 3T using ultra-low output impedance amplifiers.
abstract: Parallel transmit is an emerging technology to address the technical challenges associated with MR imaging at high field strengths. When developing arrays for parallel transmit systems, one of the primary factors to be considered is the mechanism to manage coupling and create independently operating channels. Recent work has demonstrated the use of amplifiers to provide some or all of the channel-to-channel isolation, reducing the need for on-coil decoupling networks in a manner analogous to the use of isolation preamplifiers with receive coils. This paper discusses an eight-channel transmit/receive head array for use with an ultra-low output impedance (ULOI) parallel transmit system. The ULOI amplifiers eliminated the need for a complex lumped element network to decouple the eight-rung array. The design and construction details of the array are discussed in addition to the measurement considerations required for appropriately characterizing an array when using ULOI amplifiers. B1 maps and coupling matrices are used to verify the performance of the system.
authors: Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA.
authors: Katherine Lynn
authors: KL
authors: Moody
authors: Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA.
authors: Neal A
authors: NA
authors: Hollingsworth
authors: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors: Feng
authors: F
authors: Zhao
authors: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors: Jon-Fredrik
authors: JF
authors: Nielsen
authors: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors: Douglas C
authors: DC
authors: Noll
authors: Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA; Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA; Department of Radiology, Texas A&M Health Science Center, College Station, Texas, USA.
authors: Steven M
authors: SM
authors: Wright
authors: Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA; Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA. Electronic address: mpmcdougall@tamu.edu.
authors: Mary Preston
authors: MP
authors: McDougall
mesh_terms: D000669:Amplifiers, Electronic; D004553:Electric Conductivity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014159:Transducers
keywords: Amplifier decoupling; Array coils; Coupling measurements; Isolation measurements; Parallel transmit; RF coils; Ultra-low output impedance amplifiers