Abstract
Cerebral ischemia alters the molecular dynamics and content of water in brain tissue, which is reflected in NMR relaxation, diffusion and magnetization transfer (MT) parameters. In this study, the behavior of two new MRI contrasts, Relaxation Along a Fictitious Field (RAFF) and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI), were quantified together with conventional relaxation parameters (T1, T2 and T1ρ) and MT ratios in acute cerebral ischemia in rat. The right middle cerebral artery was permanently occluded and quantitative MRI data was acquired sequentially for the above parameters for up to 6 hours. The following conclusions were drawn: 1) Time-dependent changes in RAFF and T1ρ relaxation are not coupled to those in MT. 2) RAFF relaxation evolves more like transverse, rather than longitudinal relaxation. 3) MT measured with ZAPI is less sensitive to ischemia than conventional MT. 4) ZAPI data suggest alterations in the T2 distribution of macromolecules in acute cerebral ischemia. It was shown that both RAFF and ZAPI provide complementary MRI information from acute ischemic brain tissue. The presented multiparametric MRI data may aid in the assessment of brain tissue status early in ischemic stroke.
Highlights
Transverse relaxation time (T2), diffusion and perfusion MRI are established imaging techniques used in the acute phase of ischemic stroke for both diagnosis and disease prognosis [1]
It is evident that the temporal evolutions of the relaxation parameters studied are unrelated to MT-driven processes as detected by CWMT MRI
TRAFF in brain parenchyma can be described by Bloch–McConnell equations and the changes caused by ischemia in TRAFF are predicted accurately by these equations using a two pool model [8]
Summary
Transverse relaxation time (T2), diffusion and perfusion MRI are established imaging techniques used in the acute phase of ischemic stroke for both diagnosis and disease prognosis [1]. The increase in T1r in the ischemic striatum and cortex of rat has been shown to be linear over the 6 first hour of stroke, revealing the potential to provide information about the duration of ischemia from a single time point MR scan [4]. These observations merit further exploration of rotating frame relaxations for evaluation of acute stroke, despite the fact that the exact mechanisms behind the T1r contrast in acute stroke are still much debated [5], [6], [7]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
