The authors investigated early human focal ischemia with phosphorus-31 nuclear magnetic resonance spectroscopy at 1.89 T to characterize the temporal evolution and relationship of brain pH and phosphate energy metabolism. Data from 65 symptomatic patients were prospectively studied; none of the patients had had ischemic stroke in the internal carotid artery territory before. Twenty-eight neurologically normal individuals served as control subjects. Serial ischemic brain pH levels indicated a progression from early acidosis to subacute alkalosis. When acidosis was present there was a significant elevation in the relative signal intensity of inorganic phosphate (Pi) and significant reductions in signal intensities of alpha-adenosine triphosphate (ATP) and gamma-ATP compared with those of control subjects. Ischemic brain pH values directly correlated with the relative signal intensity of phosphocreatine (PCr) and the PCr index and inversely correlated with the signal intensity of Pi. There was a general lack of correlation between either ischemic brain pH or phosphate energy metabolism and the initial clinical stroke severity. The data suggest a link between high-energy phosphate metabolism and brain pH, especially during the period of ischemic brain acidosis, and the authors propose that effective acute stroke therapy should be instituted during this period.
-8 of living systems were reported in the literature. Since that time the clinical application of NMR has experienced exponential growth. Because of this rapid pace of development and the concurrent increase in hospitalbased NMR facilities, it is timely to review the application of NMR to the diagnosis and investigation of cerebrovascular disease.Nuclear Magnetic Resonance Detailed physics of the NMR experiment are beyond the scope of this review. However, the parameters used to determine contrast in magnetic resonance imaging and the basics of NMR spectroscopy are briefly described. Magnetic Resonance Imaging (MRI)There are three parameters that determine contrast in NMR imaging: nuclear density, p, and two intrinsic NMR parameters called T, and T 2 . T, and T 2 are relaxation time constants that can have characteristic values for various tissues. By exploiting certain timing aspects of the pulse sequence (a collection of radio frequency [RF] pulses delivered in a specifically timed sequence) used in obtaining an image, one can enhance the relative contribution of p, T l5 and T 2 contrast. The time delays in the RF pulse sequence, which are adjusted to produce variable contrast, are called TR (time-to-repetition) and TE (time-to-echo). TR is related to the speed with which the entire pulse sequence is delivered, usually on the order of seconds, and TE is related to the time between the individual RF pulses within the RF pulse sequence, usually on the order of
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.