Behavioral and functional assessment of mice inner ear after chronic exposure to an ultrahigh B0 field of 11.7 T or 17.2 T

Abstract

Purpose: Assess short-term and long-term effects of chronic exposure to an ultrahigh static magnetic (B₀ ) field on mice inner ear in the context of MR safety of human scanning at 11.7 T.

Methods: Mice were chronically exposed to a B₀ field of 11.7 T or 17.2 T during ten 2-h exposure sessions evenly distributed over a period of 5 weeks, resulting in a total of 20 h of exposure per mouse. During exposure sessions, mice were anesthetized and positioned either parallel or antiparallel to B₀ . Before, during, and 2 weeks after the magnetic-field exposure period, mice performed behavioral tests (balance beam, rotarod, and swim tests) to evaluate their short-term and long-term motor coordination and balance. An auditory brainstem response (ABR) test was finally performed to assess the functional integrity of mice cochlea, 2 weeks after the last exposure.

Results: After awaking from anesthesia following B₀ exposures at 11.7 Tor 17.2 T, mice displayed a transient (<5 min) rotating behavior. The behavioral tests did not show any difference between the exposed and the control mice at any time point. Determination of ABR thresholds did not reveal an impairment of cochlea hair cells resulting from chronic B₀ exposure.

Conclusion: Despite the transient disturbance of mice vestibular system observed immediately after B₀ exposure, no short-term nor long-term alteration was detected with behavioral and ABR tests.

Keywords: auditory brainstem response; behavioral tests; ultrahigh field; vestibular system.