| Magnetic Resonance Imaging(MRI)is a non-invasive imaging technology that produces three-dimensional images.It is often used for diagnosis,and treatment monitoring.In 2020,nearly 40 million MRI scans were performed in the United States,and this number has risen significantly in recent years,reaching around 95 million the whole world.According to the Chinese Medical Doctors Association(CMDA),there were 41,182 computed tomography scans(CT)and 20,538 MRI scanners in secondary and tertiary hospitals in China in 2021.The higher imaging resolution provided by MRI scans is crucial for the early diagnosis of various diseases,such as small internal lesions,tumors,and cancer.The strength of the static magnetic field(SMF)is an important factor in achieving higher tissue resolution,imaging capability,and faster acquisition in MRI scans.Over the past few decades,the SMF strength has been increased in clinical MRI scanners,from 0.5 Tesla(T)to 3 T.Recently,7 T MRI has been approved for clinical use,and humans have been tested with 9.4 T and up to 11 T MRIs.21.1 T MRI has been used on rodents,producing superior images compared to lower field strength.This has encouraged the development of ultra-high field MRIs above 20 T,although the safety of high-field MRIs above 10 T still needs to be validated.First of all,high-strength magnetic fields need to be tested in animals for their various biological effects,including safety,neurology,immunology et al.At present,there is a limitation on animal testing for SMF exposure equal to or greater than 20 T due to limited resources.The study aimed to investigate the impact of SMF exposure on the neurophysiological functions of rodents using a water-cooled magnet(WM2),which generates SMFs ranging from 3.5 T to 23.0 T.Therefore,a series of behavioral tests were conducted to assess the effect of SMF exposure on the rodents.We systematically examined 112 mice and evaluated their short-term and long-term behavioral responses to a 2-hour SMF exposure.Five behavioral tests,including the balance beam,open field,elevated plus maze,three-chamber social recognition,and Morris water maze test,were used to measure locomotor activity and cognitive functions.The acute effect of SMFs on mice was investigated through immediate behavioral tests,including the balance beam test and open field test,performed exactly 30 minutes before and after the SMF exposure.In order to assess the prolonged impact of ultra-high static magnetic fields on rodents,three behavioral studies including an elevated plus maze,three-chamber,and Morris water maze tests were conducted from twenty days after the SMF exposure.Additionally,investigations on expression levels of key molecules in hippocampus was conducted to further reveal the mechanisms that contribute to the behavior changes observed after static magnetic fields exposure.Our study findings indicated that the 3.5-23.0 T SMF did not have any significant long-term detrimental effect on the anxiety levels,social behavior,or memory of the mice.However,it did cause temporary impairment of the sense of balance and locomotor activity,which eventually subsided.Interestingly,the study revealed anxiolytic effects and favorable effects on social and spatial memory due to exposure to SMF which was consistent with a significant increase in CaMKII level in the hippocampal area of SMF-treated mice.In conclusion,our research demonstrated that healthy mice were not adversely affected by brief exposure to high-field SMF up to 23.0 T,and it is possible that the mood and memory of mice improved due to SMF exposure.These findings contribute to the preclinical tests and evaluations of the safety of ultra-high field SMFs in MRIs. |
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