Objective

To improve sensitivity and uniformity of MR images obtained using a phased array RF coil, an inductively coupled secondary resonator with RF detuning circuits at 300 MHz was designed.

Materials and methods

A secondary resonator having detuning circuits to turn off the resonator during the transmit mode was constructed. The secondary resonator was located at the opposite side of the four-channel phased array to improve sensitivity and uniformity of the acquired MR images. Numerical simulations along with phantom and in vivo experiments were conducted to evaluate the designed secondary resonator.

Results

The numerical simulation results of |B₁⁺| in a transmit mode showed that magnetic field uniformity would be decreased with a secondary resonator having no detuning circuits because of unwanted interferences between the transmit birdcage coil and the secondary resonator. The standard deviation (SD) of |B₁⁺| was decreased 57% with a secondary resonator containing detuning circuits. The sensitivity and uniformity of |B₁⁻| in the receive mode using a four-channel phased array were improved with the secondary resonator. Phantom experiments using a uniform saline phantom had 20% improvement of the mean signal intensity and 50% decrease in the SD with the secondary resonator. Mice with excess adipose tissue were imaged to demonstrate the utility of the secondary resonator.

Conclusion

The designed secondary resonator having detuning circuits improved sensitivity and uniformity of mouse MR images acquired using the four-channel phased array.

中文翻译：

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使用电感耦合和射频失谐电路提高相控阵 MR 图像的灵敏度和均匀性。

客观的

为了提高使用相控阵射频线圈获得的 MR 图像的灵敏度和均匀性，设计了一个带有 300 MHz 射频失谐电路的电感耦合次级谐振器。

材料和方法

构造了具有在发射模式期间关闭谐振器的失谐电路的次级谐振器。次级谐振器位于四通道相控阵的另一侧，以提高所采集 MR 图像的灵敏度和均匀性。进行了数值模拟以及体模和体内实验，以评估设计的次级谐振器。

结果

|B ₁ ⁺ |的数值模拟结果 在发射模式中表明，由于发射鸟笼线圈和次级谐振器之间的干扰，没有失谐电路的次级谐振器会降低磁场均匀性。|B ₁ ⁺ |的标准偏差 (SD) 使用包含失谐电路的次级谐振器降低了 57%。|B ₁的灵敏度和均匀性^-| 在使用四通道相控阵的接收模式中，次级谐振器得到了改进。使用均匀盐水体模的体模实验的平均信号强度提高了 20%，二级谐振器的 SD 降低了 50%。对脂肪组织过多的小鼠进行成像以证明次级谐振器的效用。

结论

设计的具有失谐电路的次级谐振器提高了使用四通道相控阵采集的鼠标 MR 图像的灵敏度和均匀性。