B0 dependence of the on-resonance longitudinal relaxation time in the rotating frame (T1ρ) in protein phantoms and rat brain in vivo

✍ Scribed by Heidi I. Mäkelä; Enrico De Vita; Olli H.J. Gröhn; Mikko I. Kettunen; Martin Kavec; Mark Lythgoe; Michael Garwood; Roger Ordidge; Risto A. Kauppinen

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 102 KB
• Volume: 51
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.10669

✦ Synopsis

Abstract

On‐resonance longitudinal relaxation time in the rotating frame (T~1ρ~) 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 T~1ρ~ relaxation were assessed by determining relaxation rates (R~1ρ~) in both protein phantoms and in rat brain at 2.35, 4.7, and 9.4 T. Similar to transverse relaxation rate (R~2~), R~1ρ~ increased substantially with increasing magnetic field strength (B~0~). The B~0~ dependence was more pronounced at weak spin‐lock fields. In contrast to R~1ρ~, longitudinal relaxation rate (R~1~) decreased as a function of increasing B~0~ field. The present data argue that dipole–dipole interaction forms only one pathway for T~1ρ~ relaxation and the contributions from other physicochemical factors need to be considered. Magn Reson Med 51:4–8, 2004. © 2003 Wiley‐Liss, Inc.