中国物理B ›› 2018, Vol. 27 ›› Issue (2): 20701-020701.doi: 10.1088/1674-1056/27/2/020701

• GENERAL • 上一篇    下一篇

Performance study of aluminum shielded room for ultra-low-field magnetic resonance imaging based on SQUID: Simulations and experiments

Bo Li(李波), Hui Dong(董慧), Xiao-Lei Huang(黄小磊), Yang Qiu(邱阳), Quan Tao(陶泉), Jian-Ming Zhu(朱建明)   

  1. 1. China Jiliang University, Hangzhou 310018, China;
    2. State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology(SIMIT), Chinese Academy of Sciences(CAS), Shanghai 200050, China;
    3. CAS Center for ExcelleNce in Superconducting Electronics(CENSE), Shanghai 200050, China;
    4. University of Chinese Academy of Sciences, Beijing 100049, China
  • 收稿日期:2017-05-03 修回日期:2017-11-20 出版日期:2018-02-05 发布日期:2018-02-05
  • 通讯作者: Jian-Ming Zhu E-mail:drzhulab@gmail.com
  • 基金资助:
    Project supported in part by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB04020200) and in part by the National Natural Science Foundation of China (Grant No. 11204339).

Performance study of aluminum shielded room for ultra-low-field magnetic resonance imaging based on SQUID: Simulations and experiments

Bo Li(李波)1,2,3, Hui Dong(董慧)2,3, Xiao-Lei Huang(黄小磊)2,3,4, Yang Qiu(邱阳)1,2,3, Quan Tao(陶泉)2,3, Jian-Ming Zhu(朱建明)1   

  1. 1. China Jiliang University, Hangzhou 310018, China;
    2. State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology(SIMIT), Chinese Academy of Sciences(CAS), Shanghai 200050, China;
    3. CAS Center for ExcelleNce in Superconducting Electronics(CENSE), Shanghai 200050, China;
    4. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-05-03 Revised:2017-11-20 Online:2018-02-05 Published:2018-02-05
  • Contact: Jian-Ming Zhu E-mail:drzhulab@gmail.com
  • About author:07.55.Nk; 85.25.Dq; 87.61.-c
  • Supported by:
    Project supported in part by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB04020200) and in part by the National Natural Science Foundation of China (Grant No. 11204339).

摘要: The aluminum shielded room has been an important part of ultra-low-field magnetic resonance imaging (ULF MRI) based on the superconducting quantum interference device (SQUID). The shielded room is effective to attenuate the external radio-frequency field and keep the extremely sensitive detector, SQUID, working properly. A high-performance shielded room can increase the signal-to-noise ratio (SNR) and improve image quality. In this study, a circular coil with a diameter of 50 cm and a square coil with a side length of 2.0 m was used to simulate the magnetic fields from the nearby electric apparatuses and the distant environmental noise sources. The shielding effectivenesses (SE) of the shielded room with different thicknesses of aluminum sheets were calculated and simulated. A room using 6-mm-thick aluminum plates with a dimension of 1.5 m×1.5 m×2.0 m was then constructed. The SE was experimentally measured by using three-axis SQUID magnetometers, with tranisent magnetic field induced in the aluminum plates by the strong pre-polarization pulses. The results of the measured SE agreed with that from the simulation. In addition, the introduction of a 0.5-mm gap caused the obvious reduction of SE indicating the importance of door design. The nuclear magnetic resonance (NMR) signals of water at 5.9 kHz were measured in free space and in a shielded room, and the SNR was improved from 3 to 15. The simulation and experimental results will help us design an aluminum shielded room which satisfies the requirements for future ULF human brain imaging. Finally, the cancellation technique of the transient eddy current was tried, the simulation of the cancellation technique will lead us to finding an appropriate way to suppress the eddy current fields.

关键词: shielding effectiveness, aluminum shielded room, eddy current cancellation technique, superconducting quantum interference device, ultra-low-field magnetic resonance imaging

Abstract: The aluminum shielded room has been an important part of ultra-low-field magnetic resonance imaging (ULF MRI) based on the superconducting quantum interference device (SQUID). The shielded room is effective to attenuate the external radio-frequency field and keep the extremely sensitive detector, SQUID, working properly. A high-performance shielded room can increase the signal-to-noise ratio (SNR) and improve image quality. In this study, a circular coil with a diameter of 50 cm and a square coil with a side length of 2.0 m was used to simulate the magnetic fields from the nearby electric apparatuses and the distant environmental noise sources. The shielding effectivenesses (SE) of the shielded room with different thicknesses of aluminum sheets were calculated and simulated. A room using 6-mm-thick aluminum plates with a dimension of 1.5 m×1.5 m×2.0 m was then constructed. The SE was experimentally measured by using three-axis SQUID magnetometers, with tranisent magnetic field induced in the aluminum plates by the strong pre-polarization pulses. The results of the measured SE agreed with that from the simulation. In addition, the introduction of a 0.5-mm gap caused the obvious reduction of SE indicating the importance of door design. The nuclear magnetic resonance (NMR) signals of water at 5.9 kHz were measured in free space and in a shielded room, and the SNR was improved from 3 to 15. The simulation and experimental results will help us design an aluminum shielded room which satisfies the requirements for future ULF human brain imaging. Finally, the cancellation technique of the transient eddy current was tried, the simulation of the cancellation technique will lead us to finding an appropriate way to suppress the eddy current fields.

Key words: shielding effectiveness, aluminum shielded room, eddy current cancellation technique, superconducting quantum interference device, ultra-low-field magnetic resonance imaging

中图分类号:  (Magnetic shielding in instruments)

  • 07.55.Nk
85.25.Dq (Superconducting quantum interference devices (SQUIDs)) 87.61.-c (Magnetic resonance imaging)