Developments of rapid scans and new contrasts in ultra-low field MRI

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K20104
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Biomedical engineering and related fields
• Research Institution: Hamamatsu Photonics K.K. (2019); Kyoto University (2017-2018)
• Principal Investigator: Oida Takenori 浜松ホトニクス株式会社, 中央研究所, 専任部員 (70447910)
• Project Period (FY): 2017-06-30 – 2020-03-31
• Keywords: 超低磁場MRI / 高速撮像 / 圧縮センシング / 超解像法 / T1コントラスト改善 / 磁束密度計測 / スピンロック撮像法

Outline of Final Research Achievements

In this research, rapid imaging and pulse sequences for measuring magnetic flux densities were developed to realize the in-vivo measurements of ultra-low field MRI.
For the rapid imaging, compressed sensing and super-resolution with deep-learning techniques were applied to reduce the number of samples in the MR signal acquisition. In addition, the pulse sequences of steady state free precession and sweep imaging with Fourier transformation were assessed as rapid scan in ULF-MRI.
In the stimulus-induced rotary saturation and spin-locked Mz (SL-Mz) sequences, on the other hand, the movements of the magnetizations were analyzed with Bloch equations to confirm the effectiveness as the flux density measurements. As a result, the amplitudes and phases of measuring magnetic field were able to be obtained by the SL-Mz sequence.

Free Research Field

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Academic Significance and Societal Importance of the Research Achievements

本本研究課題で開発を進めてきた超低磁場MRIの高速撮像法や磁束密度計測法は，生体の機能計測の分野において大きなインパクトを持つ可能性があり，生体由来の微弱磁場の計測を発展させる可能性を秘めている．特に，磁束密度計測法は，微小な磁場の分布を計測できる手法であるため，生体計測のみならず，遠くの天体から飛来する宇宙磁場や地磁気変動などの天文学・地球科学の発展にも寄与する可能性があり，多くの波及効果を期待できる計測法になりうることが期待される．