Patients undergoing an MRI occasionally report seeing fiashes of light. Some practitioners assume that this results from electric stimulation of the eye by the emt induced by the rapidly changing fieids of an MRI solenoid. We can do a quick. calculation to see if this is a reasonable assumption. The human eyeball has a diameter of approximately [tex]25 \mathrm{~mm}[/tex]. Rapid changes in current in an MFI solenoid can produce rapid changes in fieid, with [tex]\Delta \mathrm{B} / \Delta \mathrm{t}[/tex] as large as [tex]50 \mathrm{~T} / \mathrm{s}[/tex]. What emt would this induce in a loop circling the eyeball? How does this compare to the [tex]15 \mathrm{mV}[/tex] necessary to trigger an action potential?
