title: Basic considerations on the impact of the coil array on the performance of Transmit SENSE.
abstract: "Transmit SENSE" adapts the idea of parallel imaging to RF transmission. Using multiple independent transmit coils, the duration of a spatially selective RF pulse can be reduced. It is known from parallel imaging that a suboptimal coil-array geometry might lead to an ill-conditioned sensitivity matrix and, thus, to a non-homogenous noise amplification in the resulting image. The current paper investigates the consequences of suboptimal coil arrays for Transmit SENSE. Two possible consequences of a suboptimal coil array are studied in the framework of numerical simulations: the incorrect excitation of the desired spatial pattern and the increase of the specific energy absorption rate (SAR), i.e. the RF power required to excite the desired pattern. Incorrect pattern excitation occurs only in pathologic coil-array scenarios. The increase of the SAR is very moderate for a large range of coil-array geometries. Using spiral excitation k-space trajectories leads to superior results compared to Cartesian trajectories. The problem of an ill-conditioned matrix inversion does not seem to play a major role in Transmit SENSE. Consequently, the freedom in designing coil arrays seems to be much larger in Transmit SENSE than in SENSE in the receive mode.
authors.affiliation: Philips Research Laboratories, Sector Technical Systems, Roentgenstrasse 24-26, D-22335, Hamburg, Germany. Ulrich.Katscher@philips.com
authors.forename: U
authors.initials: U
authors.lastname: Katscher
authors.forename: J
authors.initials: J
authors.lastname: Röhrs
authors.forename: P
authors.initials: P
authors.lastname: Börnert
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D008280:Magnetics / Q000295:instrumentation; D008954:Models, Biological; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014159:Transducers