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Physiological effects of human body imaging with 300 mT/m gradients
Molendowska, Malwina Fasano, Fabrizio Rudrapatna, Umesh Kimmlingen, Ralph Jones, Derek K. Kusmia, Slawomir Tax, Chantal M. W. Evans, C. John
Molendowska, Malwina
Fasano, Fabrizio
Rudrapatna, Umesh
Kimmlingen, Ralph
Jones, Derek K.
Kusmia, Slawomir
Tax, Chantal M. W.
Evans, C. John
Abstract
Purpose
The use of high-performance gradient systems (i.e., high gradient strength and/or high slew rate) for human MRI is limited by physiological effects (including the elicitation of magnetophosphenes and peripheral nerve stimulation (PNS)). These effects, in turn, depend on the interaction between time-varying magnetic fields and the body, and thus on the participant’s position with respect to the scanner’s isocenter. This study investigated the occurrence of magnetophosphenes and PNS when scanning participants on a high-gradient (300 mT/m) system, for different gradient amplitudes, ramp times, and participant positions.
Methods
Using a whole-body 300 mT/m gradient MRI system, a cohort of participants was scanned with the head, heart, and prostate at magnet isocenter and a train of trapezoidal bipolar gradient pulses, with ramp times from 0.88 to 4.20 ms and gradient amplitudes from 60 to 300 mT/m. Reports of magnetophosphenes and incidental reports of PNS were obtained. A questionnaire was used to record any additional subjective effects.
Results
Magnetophosphenes were strongly dependent on participant position in the scanner. 87% of participants reported the effect with the heart at isocenter, 33% with the head at isocenter, and only 7% with the prostate at isocenter. PNS was most widely reported by participants for the vertical gradient axis (67% of participants), and was the dominant physiological effect for ramp times below 2 ms.
Conclusion
This study evaluates the probability of eliciting magnetophosphenes during whole-body imaging using an ultra-strong gradient MRI system. It provides empirical guidance on the use of high-performance gradient systems for whole-body human MRI.
Keywords
gradient switching fields, magnetic fields, magnetophosphenes, peripheral nerve stimulation, ultra-strong gradient system
Date
2022
Type
Journal article
Journal
Magnetic Resonance in Medicine
Book
Volume
87
Issue
5
Page Range
2512-2520
Article Number
ACU Department
Collections
Relation URI
Source URL
Event URL
Open Access Status
Published as ‘gold’ (paid) open access
License
CC BY 4.0
File Access
Open