Non-invasive evaluation of cerebral perfusion in patients with transient ischemic attack: an fMRI study

Detection of hypoperfused tissue due to the ischemia is considered to be important in understanding the cerebral perfusion status and may be helpful in guiding therapeutic decisions for patients with transient ischemic attack (TIA). We hypothesized that the combination of two non-invasive fMRI techniques: resting-state BOLD-fMRI time-shift analysis (TSA) approach and 3D ASL, could detect the cerebral hemodynamic status in TIA patients noninvasively. From April 2015 to June 2016, 51 TIA patients were recruited in this study. We calculated the time delay between the resting-state BOLD signal at each voxel and the whole-brain signal using TSA approach and compared the results to CBF map derived from ASL. Out of the 51 patients, 24 patients with normal arrival time and CBF were in Stage 0; 14 patients who showed delayed arrival time and normal CBF which indicated elevated CBV were in Stage I; the other 13 patients who had both delayed arrival time and decreased CBF were in Stage II, the group average spatial overlap, i.e., Dice coefficient, of the two measurements was 0.55. Four patients in Stage 0 (17.4%), three patients in Stage I (23.1%) and five patients in Stage II (45.5%) suffered ischemic stroke or TIA symptoms in 1 year after MRI scan. The patients in Stage II was at highest risk of subsequent events when compared to other two stages. The combination of resting-state BOLD-fMRI and ASL hold the potential to noninvasively identify the hemodynamic status in TIA patients and help predict the risk of subsequent events.