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CEST phase mapping using a length and offset varied saturation (LOVARS) scheme
Author(s) -
Song Xiaolei,
Gilad Assaf A.,
Joel Suresh,
Liu Guanshu,
BarShir Am,
Liang Yajie,
Gorelik Michael,
Pekar James J.,
van Zijl Peter C. M.,
Bulte Jeff W. M.,
McMahon Michael T.
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.23312
Subject(s) - offset (computer science) , saturation (graph theory) , magnetization transfer , contrast (vision) , phase contrast microscopy , nuclear magnetic resonance , chemistry , materials science , analytical chemistry (journal) , physics , optics , computer science , magnetic resonance imaging , mathematics , radiology , medicine , chromatography , combinatorics , programming language
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 B 0 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 B 0 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 B 0 artifacts. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.