Static magnetic fields dampen focused ultrasound- mediated blood-brain barrier opening

Yaoheng Yang, Christopher Pham Pacia, Dezhuang Ye, Yimei Yue, Chih Yen Chien, Hong Chen

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Background: Focused ultrasound combined with microbubbles has been used in clinical studies for blood-brain barrier (BBB) opening in conjunction with MRI. However, the impact of the static magnetic field generated by an MRI scanner on the BBB opening outcome has not been evaluated. Purpose: To determine the relationship of the static magnetic field of an MRI scanner on focused ultrasound combined with microbubble- induced BBB opening. Materials and Methods: Thirty wild-type mice were divided into four groups. Mice from different groups were sonicated with focused ultrasound in different static magnetic fields (approximately 0, 1.5, 3.0, and 4.7 T), with all other experimental parameters kept the same. Focused ultrasound sonication was performed after intravenous injection of microbubbles. Microbubble cavitation activity, the fundamental physical mechanism underlying focused ultrasound BBB opening, was monitored with passive cavitation detection. After sonication, contrast-enhanced T1-weighted MRI was performed to assess BBB opening outcome. Intravenously injected Evans blue was used as a model agent to evaluate trans-BBB delivery efficiency. Results: The microbubble cavitation dose decreased by an average of 2.1 dB at 1.5 T (P = .05), 2.9 dB at 3.0 T (P = .01), and 3.0 dB at 4.7 T (P = .01) compared with that outside the magnetic field (approximately 0 T). The static magnetic field of an MRI scanner decreased BBB opening volume in mice by 3.2-fold at 1.5 T (P <001), 4.5-fold at 3.0 T (P <.001), and 11.6-fold at 4.7 T (P <.001) compared with mice treated outside the magnetic field. It also decreased Evans blue trans-BBB delivery 1.4-fold at 1.5 T (P = .009), 1.6-fold at 3.0 T (P <.001), and 1.9-fold at 4.7 T (P <.001). Conclusion: Static magnetic fields dampened microbubble cavitation activity and decreased trans-blood-brain barrier (BBB) delivery by focused ultrasound combined with microbubble-induced BBB opening.

Original languageEnglish
Pages (from-to)681
Number of pages1
Issue number3
StatePublished - Sep 2021


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