Name
Abstract | ||
|---|---|---|
Chemical exchange between water and labile protons from amino-acids, proteins and other molecules can be exploited to provide tissue contrast with magnetic resonance imaging (MRI) techniques. Using an off-resonance Spin-Locking (SL) scheme for signal preparation is advantageous because the image contrast can be tuned to specific exchange rates by adjusting SL pulse parameters. While the amide–proton transfer (APT) contrast is obtained optimally with steady-state preparation, using a low power and long irradiation pulse, image contrast from the faster amine–water proton exchange (APEX) is optimized in the transient state with a higher power and a shorter SL pulse. Our phantom experiments show that the APEX contrast is sensitive to protein and amino acid concentration, as well as pH. In vivo 9.4-T SL MRI data of rat brains with irradiation parameters optimized to slow exchange rates have a sharp peak at 3.5ppm and also broad peak at −2 to −5ppm, inducing negative contrast in APT-weighted images, while the APEX image has large positive signal resulting from a weighted summation of many different amine-groups. Brain ischemia induced by cardiac arrest decreases pure APT signal from ~1.7% to ~0%, and increases the APEX signal from ~8% to ~16%. In the middle cerebral artery occlusion (MCAO) model, the APEX signal shows different spatial and temporal patterns with large inter-animal variations compared to APT and water diffusion maps. Because of the similarity between the chemical exchange saturation transfer (CEST) and SL techniques, APEX contrast can also be obtained by a CEST approach using similar irradiation parameters. APEX may provide useful information for many diseases involving a change in levels of proteins, peptides, amino-acids, or pH, and may serve as a sensitive neuroimaging biomarker. |
Year | DOI | Venue |
|---|---|---|
2012 | 10.1016/j.neuroimage.2011.08.014 | NeuroImage |
Keywords | Field | DocType |
Amine–water proton exchange,Spin-locking MRI,Amino acids,Proteins,Ischemia,Amide–proton transfer,Chemical exchange saturation transfer | Nuclear medicine,Proton,Saturation (chemistry),Molecule,Apex (geometry),Imaging phantom,Irradiation,Psychology,Cognitive psychology,Pulse (signal processing),Nuclear magnetic resonance,Magnetic resonance imaging | Journal |
Volume | Issue | ISSN |
59 | 2 | 1053-8119 |
Citations | PageRank | References |
4 | 1.01 | 2 |
Authors | ||
4 | ||
Name | Order | Citations | PageRank |
|---|---|---|---|
| Tao Jin | 1 | 4 | 1.01 |
| Ping Wang | 2 | 4 | 1.01 |
| Xiaopeng Zong | 3 | 28 | 3.42 |
| Seong-Gi Kim | 4 | 403 | 55.43 |