School of Dynamic Systems, Mechanical Engineering, University of Cincinnati, Cincinnati, Ohio, USA.
J Magn Reson Imaging. 2011 Sep;34(3):662-9. doi: 10.1002/jmri.22694. Epub 2011 Jul 12.
To evaluate the effectiveness of the proposed active noise control (ANC) system for the reduction of the acoustic noise emission generated by a 4 T MRI scanner during operation and to assess the feasibility of developing an ANC device that can be deployed in situ.
Three typical scanning sequences, EPI (echo planar imaging), GEMS (gradient echo multislice), and MDEFT (modified driven equilibrium Fourier transform), were used for evaluating the performance of the ANC system, which was composed of a magnetic compatible headset and a multiple reference feedforward filtered-x least mean square controller.
The greatest reduction, about 55 dB, was achieved at the harmonic at a frequency of 1.3 kHz in the GEMS case. Approximately 21 dB and 30 dBA overall reduction was achieved for GEMS noise across the entire audible frequency range. For the MDEFT sequence, the control system achieved 14 dB and 14 dBA overall reduction in the audible frequency range, while 13 dB and 14 dBA reduction was obtained for the EPI case.
The result is highly encouraging because it shows great potential for treating magnetic resonance imaging noise with an ANC application during real-time scanning.
评估所提出的有源噪声控制（ANC）系统在降低运行中 4T MRI 扫描仪产生的声学噪声排放方面的有效性，并评估开发可现场部署的 ANC 设备的可行性。
使用三种典型的扫描序列，EPI（回波平面成像）、GEMS（梯度回波多层）和 MDEFT（改良驱动平衡傅里叶变换），评估 ANC 系统的性能，该系统由磁兼容耳机和多个参考前馈滤波-x 最小均方控制器组成。
在 GEMS 情况下，在频率为 1.3kHz 的谐波处获得了最大的约 55dB 的降低。在整个可听频率范围内，GEMS 噪声的总降低约为 21dB 和 30dBA。对于 MDEFT 序列，控制系统在可听频率范围内实现了 14dB 和 14dBA 的总降低，而对于 EPI 情况，则获得了 13dB 和 14dBA 的降低。
结果令人鼓舞，因为它显示出在实时扫描期间使用 ANC 应用治疗磁共振成像噪声的巨大潜力。
