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Multi‐angle ratiometric approach to measure chemical exchange in amide proton transfer imaging
Author(s) -
Zu Zhongliang,
Janve Vaibhav A.,
Li Ke,
Does Mark D.,
Gore John C.,
Gochberg Daniel F.
Publication year - 2012
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.23276
Subject(s) - magnetization transfer , chemistry , saturation (graph theory) , amide , nuclear magnetic resonance , proton , analytical chemistry (journal) , rotation (mathematics) , chemical reaction , chemical physics , magnetic resonance imaging , chromatography , organic chemistry , geometry , medicine , physics , mathematics , combinatorics , quantum mechanics , radiology
Amide proton transfer imaging, a specific form of chemical exchange saturation transfer imaging, has previously been applied to studies of acute ischemic acidosis, stroke, and cancer. However, interpreting the resulting contrast is complicated by its dependence on the exchange rate between amides and water, the amide concentration, amide and water relaxation, and macromolecular magnetization transfer. Hence, conventional chemical exchange saturation transfer contrast is not specific to changes such as reductions in pH due to tissue acidosis. In this article, a multi‐angle ratiometric approach based on several pulsed‐chemical exchange saturation transfer scans at different irradiation flip angles is proposed to specifically reflect exchange rates only. This separation of exchange effects in pulsed‐chemical exchange saturation transfer experiments is based on isolating rotation vs. saturation contributions, and such methods form a new subclass of chemical exchange rotation transfer (CERT) experiments. Simulations and measurements of creatine/agar phantoms indicate that a newly proposed imaging metric isolates the effects of exchange rate changes, independent of other sample parameters. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.