Alice Rousseau, our MRI test engineer, tells you a little bit more about the magnetically induced Force testing.
” Healtis carries out the assessment of the MRI static magnetic field induced displacement force on a medical device, according to ASTM F2052; the latest version of which was published in 2021.
We conduct this test using a clinical 3 Tesla MRI scanner. The tested device is suspended from a string and moved closer to the MR bore entrance until the maximum angle from the vertical is induced on the string. This deflection angle is directly proportional to the force of attraction. The ambient conditions of the magnetic field are also measured, where this maximum angle is read, in order to associate the force of attraction with an exposure seen by the device. The data then allows for the extrapolation of the measurement for any exposure, in particular, it is possible to determine the maximum exposure to meet a given acceptance criterion.
A conservative acceptance criterion, suggested by the standard, is the weight of the device, considering that a force of attraction lower than the weight to which the device is subjected every day is largely acceptable.
However, less conservative criteria can be used, considering in particular the resistance of the tissues in contact with the device, or the mode of implantation of the device, if sutured for example.
A group of experts is currently working on an extension of the standard which aims to present a test method for large devices, which cannot be suspended from a string.
However, pending a normative method, this type of device can already be evaluated according to a specifically defined method, adapting if necessary.”
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