Phillip Zhe Sun1, Enfeng Wang1, Jerry S. Cheung1
1Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States
Amide proton transfer (APT) MRI is capable of imaging tissue acidosis during acute stroke. However, magnetization transfer asymmetry (MTRasym) is often calculated for pH-weighted APT contrast, which is subject to a baseline shift (MTRasym) attributable to the slightly asymmetric magnetization transfer (MT) effect. In this study, we modeled MTRasym as a superposition of pH-dependent APT contrast and a baseline shift MTRasym (i.e., MTRasym=APTR(pH) + MTRasym). We found schemic lesion pH was 6.44 0.24, significantly reduced from that of the normal tissue (7.03 0.05), which correlated with tissue perfusion and diffusion rates.