title: B0 dependence of the on-resonance longitudinal relaxation time in the rotating frame (T1rho) in protein phantoms and rat brain in vivo.
abstract: On-resonance longitudinal relaxation time in the rotating frame (T1rho) has been shown to provide unique information during the early minutes of acute stroke. In the present study, the contributions of the different relaxation mechanisms to on-resonance T1rho relaxation were assessed by determining relaxation rates (R1rho) in both protein phantoms and in rat brain at 2.35, 4.7, and 9.4 T. Similar to transverse relaxation rate (R2), R1rho increased substantially with increasing magnetic field strength (B0). The B0 dependence was more pronounced at weak spin-lock fields. In contrast to R1rho, longitudinal relaxation rate (R1) decreased as a function of increasing B0 field. The present data argue that dipole-dipole interaction forms only one pathway for T1rho relaxation and the contributions from other physicochemical factors need to be considered.
authors.affiliation: Department of Biomedical NMR and National Bio-NMR Facility, AI Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland.
authors.forename: Heidi I
authors.initials: HI
authors.lastname: Mäkelä
authors.forename: Enrico
authors.initials: E
authors.lastname: De Vita
authors.forename: Olli H J
authors.initials: OH
authors.lastname: Gröhn
authors.forename: Mikko I
authors.initials: MI
authors.lastname: Kettunen
authors.forename: Martin
authors.initials: M
authors.lastname: Kavec
authors.forename: Mark
authors.initials: M
authors.lastname: Lythgoe
authors.forename: Michael
authors.initials: M
authors.lastname: Garwood
authors.forename: Roger
authors.initials: R
authors.lastname: Ordidge
authors.forename: Risto A
authors.initials: RA
authors.lastname: Kauppinen
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D003432:Cross-Linking Reagents; D005976:Glutaral; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D019047:Phantoms, Imaging; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D012710:Serum Albumin, Bovine / Q000737:chemistry
chemical_list: D003432:Cross-Linking Reagents; D011506:Proteins; D012710:Serum Albumin, Bovine; D005976:Glutaral