CEST phase mapping using a length and offset varied saturation (LOVARS) scheme.

TitleCEST phase mapping using a length and offset varied saturation (LOVARS) scheme.
Publication TypeJournal Article
Year of Publication2012
AuthorsSong X, Gilad AA, Joel S, Liu G, Bar-Shir A, Liang Y, Gorelik M, Pekar JJ, van Zijl PCM, Bulte JWM, McMahon MT
JournalMagnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine
Volume68
Issue4
Pagination1074-86
Date Published2012 Oct
Abstract

Chemical exchange saturation transfer MRI is a promising new technique for cellular and molecular imaging. This contrast allows the detection of tumors and ischemia without the use of gadolinium as well as the design of microenvironment-sensitive probes that can be discriminated based on their exchange contrast properties and saturation frequency. Current acquisition schemes to detect and analyze this contrast suffer from sensitivity to spatial B0 inhomogeneity and low contrast-to-noise-ratio, which is an obstacle to widespread adoption of the technology. A new method to detect chemical exchange saturation transfer contrast is proposed here, termed "length and offset varied saturation" which acquires a set of images with the saturation parameters varied so as to modulate the exchange contrast. Either fast fourier transform or the general linear model can be employed to decompose the modulation patterns into separate sources of water signal loss. After transformation, a length and offset varied saturation phase map is generated, which is insensitive to B0 inhomogeneity. When collected on live mice bearing 9L gliosarcomas, and compared to the conventional asymmetry in the magnetization transfer ratio map using offset increment correction, the results show that length and offset varied saturation phase mapping obtains about three to four times contrast-to-noise-ratio and exhibits less B0 artifacts.

DOI10.1007/s12975-011-0110-4
Alternate JournalMagn Reson Med