Figure 8. Example patient highlighting the multiple difficulties of performing APT imaging in human acute stroke patients.

(a) The acute FLuid Attenuated Inversion Recovery (FLAIR) image denotes clear motion artifacts, which were observed in the majority of patients, as well as a right-sided prior infarct (purple arrow). (b) The segmentation results showing a large ischemic penumbra. In this patient, the region of diffusion weighted imaging (DWI) contrast largely co-localized with the final infarct volume (green). (c) The APT map shows less asymmetry than apparent in the patient presented in Fig. 4, which is partly consistent with more limited tissue acidosis. However, high APT values are observed in the sulcus on the right, which partial volumes with CSF. Additionally, regions of the right frontal lobe exhibit apparent reduced APT effects, yet these regions do not progress to infarct and in some instances appear to partial volume with the chronic infarct. Improved approaches for correcting motion and partial volume effects are likely required before more widespread testing of APT is pursued in acute stroke patients.