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This study investigates the effect of the tuning conditions and losses of a radiofrequency birdcage coil on the incident field generated in a phantom. Several numerical implementations of a birdcage body coil model with variable coil losses were studied. The results showed that magnetic field at the coil isocenter (||H||iso), normalized to the square root of the whole body specific absorption rate,...
This study investigates how the tuning conditions of a 64 MHz / 1.5 T radio frequency (RF) birdcage coil modeled with an RF circuit and 3D electromagnetic co-simulation affect the electric and magnetic near-field distribution. Four models were implemented with different tuning conditions and difference between numerical results and measurements was evaluated. The results show that the simulated near-field...
Radio frequency (RF) induced power deposition near straight insulated leads excited by different incident electrical field profiles was investigated. 3-D electromagnetic (EM) simulations were used to obtain implant models as well as RF-induced power depositions calculated as the integral of power loss density. For the investigated setups up to 400% discrepancy between the implant model predictions...
We investigated effects of the geometry and size of the cerebrospinal fluid (CSF) on transmit and safety efficiencies in magnetic resonance imaging at 300 MHz. For the human model investigated here and a head position at the top of the RF coil, an increase of CSF space resulted in essential degradation of the safety excitation efficiency without an easily recognizable influence on the magnetic field...
We provide recommendations for simulation-driven design and work-flow for magnetic resonance imaging RF transmit-coil arrays. To enable final decisions on array construction, accurate knowledge is needed of how the array transmit and safety measures depend on the array geometry, RF component losses, and the tuning and excitation conditions. If strong evidence is provided that array safety excitation...
We numerically investigated several magnetic resonance imaging radiofrequency transmit coil arrays, with and without a local shield, and with a range of scanner bore configurations. The latter had a significant influence on safety excitation efficiency. It is therefore important to include the scanner magnet room in the simulation domain, when the scanner bore is not isolated from the rest of the...
We present a numerical investigation of the RF fields generated inside a human head by single and dual-row loop arrays. For a uniform circular polarization (CP) mode excitation, a dual-row array has no advantage for human brain excitation. Significant improvement of B1+ homogeneity with a simultaneous increase of coverage in the axial direction can be obtained by using a dual-row array together with...
We present numerical investigation for a set of loop array geometry/load configurations obtained by RF circuit and frequency domain 3-D EM co-simulation. This is a very powerful and fast method for array coil investigation, since one multi-port 3-D EM simulation, which can be calculated in a reasonable time, is sufficient for obtaining the array transmit properties with several tuning/feeding/decoupling...
We present a numerical investigation of the near radiofrequency fields generated by a set of multi-row multichannel MRI loop array at 300 and 400 MHz using RF circuit and frequency domain 3-D EM co-simulation. Significant improvement of B1+ homogeneity with a simultaneous increase of coverage in the axial direction can be obtained by using a multi-row array together with a static volume RF shim. At...
We present a numerical investigation of the RF fields generated by a parameterized set of loop array configurations using RF circuit and frequency domain 3-D EM co-simulation. When circular polarization mode excitation of the entire human brain is used, single row arrays with the closest possible element spacing, whether of 4, 8 or 12 elements, deliver the largest fraction of the available transmit...
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