Figure 2.

(a) R₁ maps for a single patient at three time points: pre-ultrasmall superparamagnetic particles of iron oxide (USPIO) (scan 1_pre), immediately post-USPIO (scan 1_post), and at 24–30 h post-USPIO (scan 2). The corresponding relative flip angle (i.e., k: the actual flip angle divided by the nominal value) map measured at baseline is shown on the right, illustrating both variation due to B₁ inhomogeneity and the (axial) slab excitation profile; (b) R₂* maps in the same patient, obtained at the same time points and at 1 month post-USPIO (scan 3); (c) Parametric maps in another patient (79 year old male, first visit 31 days post-infarct in the left basal ganglia). R₁ is seen to increase visibly in the stroke lesion following USPIO administration. The corresponding change to R₂* is more subtle in the stroke lesion, but a visible increase is seen in the neighbouring background tissue.