In vivo NMR imaging of tissue sodium in the intact cat before and after acute cerebral stroke.

The first in vivo nuclear magnetic resonance (NMR) images of tissue sodium in the intact animal are presented. The distribution of sodium in the normal cat's head is described. An experimental stroke was surgically induced. Sodium NMR imaging showed a pronounced focal increase in cerebral sodium concentration 9 hr after ligation of the middle cerebral artery. The method appears to be very sensitive for early detection of infarction. The measured increase in the regional sodium NMR signal probably reflects both a true increase in concentration of brain sodium and an increased NMR visibility of the sodium nucleus in the region of the infarction.