Field-Cycling MRI for Identifying Minor Ischemic Stroke Below 0.2 T

Area of Science:

• Medical Imaging
• Biophysics
• Neurology

Background:

• Field-cycling imaging (FCI) measures T1 relaxation time constants across a range of low magnetic fields (0.2-200 mT).
• FCI offers novel contrast mechanisms potentially useful for stroke detection, beyond conventional MRI capabilities.
• This technology was developed at the University of Aberdeen.

Purpose of the Study:

• To evaluate a prototype whole-body FCI scanner for identifying infarct regions in subacute ischemic stroke patients.
• To assess the feasibility of using FCI as an alternative imaging modality for stroke.

Main Methods:

• Prospective study of adult patients with confirmed ischemic stroke admitted to a stroke unit.
• FCI scans acquired 1-6 days post-ictus at 0.2 mT to 0.2 T with varying evolution times.
• T1 maps generated; infarct regions compared to contralateral unaffected brain using Wilcoxon signed-rank test.

Main Results:

• FCI scans below 0.2 T showed hyperintense T1 regions corresponding to infarcts, with 86% interrater agreement.
• Infarct-to-contralateral tissue contrast increased as magnetic field strength decreased (r = -0.68, P < .001).
• T1 dispersion slopes differed significantly between infarct and unaffected tissues (P = .03).

Conclusions:

• Whole-brain FCI effectively identifies subacute ischemic stroke using T1 relaxation mechanisms.
• FCI can detect stroke at magnetic field strengths as low as 0.2 mT.
• This technique demonstrates potential as a valuable tool in stroke imaging.