T1 discrimination contributions to proton magnetization transfer in heterogeneous biological systems

✍ Scribed by Hua Yang; Thomas Schleich

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 816 KB
• Volume: 32
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910320104

✦ Synopsis

Abstract

Water proton spin‐lattice relaxation times are commonly used as a guide in establishing the off‐resonance irradiation time as well as the repetition time of the magnetization transfer experiment. T~1~ discrimination effects occur if the motionally restricted spin bath longitudinal magnetization does not reach thermal equilibrium. In this study we developed the formalism necessary for the evaluation of T~1~ discrimination contributions to proton magnetization transfer arising from the use of a short repetition time relative to the spin‐lattice relaxation time of the motionally restricted spin bath. The results of computer simulation indicate that T~1~, discrimination contributions occur when the repetition time is small relative to the spin‐lattice relaxation time of the motionally restricted spin bath, and when the off‐resonance irradiation is weak and far off‐resonance. For somewhat longer repetition times, T~1~ discrimination contributions become important only when the cross relaxation rate is small, and the fractional amount of motionally restricted component large. The occurrence of T~1~ discrimination effects results in distortion of water proton intensity ratio dispersion curves thereby resulting in the estimation of erroneous magnetization transfer parameters, whereas in magnetization transfer contrast enhanced imaging, such contributions are manifested by a decrease in image contrast.