UCEPR: Ultrafast localized CEST-spectroscopy with PRESS in phantoms and in vivo

• Published in: Magnetic resonance in medicine 2016-05, Vol.75 (5), p.1875-1885
• Main Authors: Liu, Zheng, Dimitrov, Ivan E., Lenkinski, Robert E., Hajibeigi, Asghar, Vinogradov, Elena
• Format: Article
• Language: English
• Subjects: APT; Brain - diagnostic imaging; Brain - physiology; broadband saturation; Contrast Media - chemistry; Healthy Volunteers; Humans; Hydrogen-Ion Concentration; Image Processing, Computer-Assisted - methods; iopamidol; Iopamidol - chemistry; Magnetic Resonance Imaging; Methods; Phantoms, Imaging; PRESS; Protons; Radio Waves; Spectrophotometry - methods; Spectrum analysis; ultrafast localized CEST; Water - chemistry
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.25780

Purpose Chemical exchange saturation transfer (CEST) is a contrast mechanism enhancing low‐concentration molecules through saturation transfer from their exchangeable protons to bulk water. Often many scans are acquired to form a Z‐spectrum, making the CEST method time‐consuming. Here, an ultrafast localized CEST‐spectroscopy with PRESS (UCEPR) is proposed to obtain the entire Z‐spectrum of a voxel using only two scans, significantly accelerating CEST. Theory and Methods The approach combines ultrafast nonlocalized CEST spectroscopy with localization using PRESS. A field gradient is applied concurrently with the saturation pulse producing simultaneous saturation of all Z‐spectrum frequencies that are also spatially encoded. A readout gradient during data acquisition resolves the spatial dependence of the CEST responses into frequency. UCEPR was tested on a 3T scanner both in phantoms and in vivo. Results In phantoms, a fast Z‐spectroscopy acquisition of multiple pH‐variant iopamidol samples was achieved with four‐ to seven‐fold acceleration as compared to the conventional CEST methods. In vivo, amide proton transfer (APT) in white matter of healthy human brain was measured rapidly in 48 s and with high frequency resolution (≤ 0.2 ppm). Conclusion Compared with conventional CEST methods, UCEPR has the advantage of rapidly acquiring high‐resolution Z‐spectra. Potential in vivo applications include ultrafast localized Z‐spectroscopy, quantitative, or dynamic CEST studies. Magn Reson Med 75:1875–1885, 2016. © 2015 Wiley Periodicals, Inc.