Magnetic shieldless ultra-low-field MRI with an optically pumped magnetometer
Magnetic shieldless ultra-low-field MRI with an optically pumped magnetometer
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DOI：
10.1016/j.jmr.2022.107280
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发表时间：
2022-08-20
影响因子：
2.2
通讯作者：
Kobayashi, Tetsuo
中科院分区：
文献类型：
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作者：
Hori, Sogo;Oida, Takenori;Kobayashi, Tetsuo
在磁共振成像 (MRI) 技术中，超低场 (ULF) MRI 有可能显着降低实施和维护成本以及扫描系统的尺寸。由于 ULR-MRI 产生的信号幅度较小，因此需要极其灵敏的磁传感器。光泵磁力计 (OPM) 已被提议在 ULF-MRI 中用作能够检测非常小信号的超灵敏磁传感器。然而，铁磁磁屏蔽的成本对于许多应用来说通常是负担不起的。通过提高拉莫尔频率，可以减轻低频磁噪声的影响，从而允许 OPM 在不使用磁屏蔽室的情况下运行。这降低了磁屏蔽的成本，并进一步提高了信号强度，从而带来了非预极化等好处。在本研究中，我们提出了一种使用低成本 OPM 实施 ULF-MRI 的方法。将拉莫尔频率调整至 300 kHz，使用 7.05 mT 的静磁场，在不使用磁屏蔽室或预极化线圈的情况下，以 3 x 3 x 3 mm3 的数字分辨率获取体模的三维 (3D) 图像。此外，我们校正了采集图像的频率响应以考虑窄带宽，3D 成像的 SNR 为 18。我们相信，实验结果为不需要昂贵的磁屏蔽的高性能、低成本 ULF-MRI 建立了新的指导原则。(c) 2022 Elsevier Inc. 保留所有权利。
Among magnetic resonance imaging (MRI) techniques, ultra-low field (ULF) MRI has the potential to sig-nificantly lower the cost of implementation and maintenance, as well as the size of the scanning system. Due to the small amplitude of the signals produced by ULR-MRI, extremely sensitive magnetic sensors are required. Optically pumped magnetometers (OPMs) have been proposed for use in ULF-MRI as ultra-sensitive magnetic sensors capable of detecting very small signals. However, the cost of a ferromagnetic magnetic shield is often not affordable for many applications. By increasing the Larmor frequency, the influence of low-frequency magnetic noise can be mitigated, allowing OPM to be operated without the use of a magnetic shield chamber. This lowers the cost of the magnetic shield and further raises the signal strength, resulting in benefits such as non-prepolarization. We present a method for implementing the ULF-MRI using low-cost OPMs in this study. The Larmor frequency was adjusted to 300 kHz, and three-dimensional (3D) images of a phantom were acquired with a digital resolution of 3 x 3 x 3 mm3 using a static magnetic field of 7.05 mT without using a magnetic shield room or a pre-polarization coil. Additionally, we corrected the frequency response to acquired images to consider the narrow bandwidth, and the SNR of 3D imaging was 18. The experimental results, we believe, establish a new guideline for higher-performance, lower-cost ULF-MRI that does not require expensive magnetic shielding.(c) 2022 Elsevier Inc. All rights reserved.