title: Long-lived spin states as a source of contrast in magnetic resonance spectroscopy and imaging.
abstract: A method is proposed to create Long-Lived spin States (LLSs) from longitudinal spin magnetization, which is based on adiabatic switching of a Radio-Frequency (RF) field with proper frequency. The technique is simple to implement with standard Nuclear Magnetic Resonance (NMR) equipment, providing an excellent conversion of population from the triplet T+ (or T-) state to the singlet state of a pair of spins and back. The method has been tested for the amino acid tyrosine and its partially deuterated isotopomer; for the deuterated compound, we have achieved a LLS lifetime, which exceeds the longitudinal relaxation time by a factor of 21. Furthermore, by slightly modifying the method, an enhanced contrast with respect to LLSs in NMR spectra is achieved; contrast enhancements of more than 1200 are feasible. This enables efficient suppression of longitudinal spin magnetization in NMR allowing one to look selectively at LLSs. Using this method we have demonstrated that not only spectral but also spatial contrast can be achieved: we have obtained spatial NMR images with strongly improved contrast originating from the difference of LLS lifetimes at different positions in the sample.
authors.affiliation: International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
authors.forename: Alexey S
authors.initials: AS
authors.lastname: Kiryutin
authors.affiliation: Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, Heidelberg 69120, Germany.
authors.forename: Herbert
authors.initials: H
authors.lastname: Zimmermann
authors.affiliation: International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Yurkovskaya
authors.affiliation: International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany.
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Vieth
authors.affiliation: International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia. Electronic address: ivanov@tomo.nsc.ru.
authors.forename: Konstantin L
authors.initials: KL
authors.lastname: Ivanov
keywords: Contrast; Long-lived spin states; MRI; NMR relaxation