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3.0 T MRI를 위한 Parallel-Transmission RF 코일 구조의 비교와 최적화
오창현(Chang-Hyun Oh),이흥규(Heung K. Lee),류연철(Yeun-Chul Ryu),현정호(Jung-Ho Hyun),최혁진(Hyuk-Jin Choi) 대한전기학회 2007 대한전기학회 학술대회 논문집 Vol.2007 No.4
In high field (> 3 T) MR imaging, the magnetic field inhomogeneity in the target object increases due to the nonuniform electro-magnetic characteristics and relatively high Larmor frequency. Especially in the body imaging, the effect causes more serious problems resulting in locally high SAR(Specific Absorption Ratio). In this paper, we propose an optimized parallel-transmission RF coil element structure and show the utility of the coil by FDTD simulations to overcome the unwanted effects. Three types of TX coil elements are tested to maximize the efficiency and their driving patterns(amplitude and phase) optimized to have adequate field homogeneity, proper SAR level, and sufficient field strength. For the proposed coil element of 25 ㎝ × 8 ㎝ loop structure with 12 channels for a 3.0 T body coil, the 73% field non-uniformity without optimization was reduced to about 26% after optimization of driving patterns. The experimental as well as simulation results show the utility of the proposed parallel driving scheme is clinically useful for (ultra) high field MRI.
류연철(Yeun-chul Ryu),현정호(Jung-ho Hyun),이흥규(Heung K. Lee),오창현(Chang-Hyun Oh) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10
In this paper, the previous 2-D gradient coil design method using loop current clements is extended [0 3-D or multi-layer structures which is useful for various MRI applications including MIl microscopic imaging where relatively large space may be available for the implementation of the gradient coils. Either the power consumption or the stored energy (thus, inductance). or the combination of the two can be minimized with a set of chosen target field constraints. Complete 3-D design equations for the optimization as well us inductance or resistance calculation are derived. An effective coil shape correction method for a curved current pattern is also developed. The design method can also be easily extended to the active shielding structure.