Premium
Multi‐echo Length and Offset VARied Saturation (MeLOVARS) method for improved CEST imaging
Author(s) -
Song Xiaolei,
Xu Jiadi,
Xia Shuli,
Yadav Nirbhay N.,
Lal Bachchu,
Laterra John,
Bulte Jeff W.M.,
van Zijl Peter C.M.,
McMahon Michael T.
Publication year - 2015
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.25567
Subject(s) - saturation (graph theory) , nuclear magnetic resonance , offset (computer science) , flip angle , echo time , physics , nuclear medicine , chemistry , magnetic resonance imaging , mathematics , computer science , medicine , combinatorics , radiology , programming language
Purpose The aim of this study was to develop a technique for rapid collection of chemical exchange saturation transfer images with the saturation varied to modulate signal loss transfer and enhance contrast. Methods Multi‐echo Length and Offset VARied Saturation (MeLOVARS) divides the saturation pulse of length T sat into N = 3–8 submodules, each consisting of a saturation pulse with length of T sat /N (∼0.3–1 s), one or more low flip‐angle gradient‐echo readout(s) and a flip back pulse. This results in N readouts with increasing saturation time from T sat /N to T sat without extra scan time. Results For phantoms, eight images with T sat incremented every 0.5 s from 0.5–4 s were collected simultaneously using MeLOVARS, which allows rapid determination of exchange rates for agent protons. For live mice bearing glioblastomas, the Z‐spectra for five different T sat values from 0.5 to 2.5 s were acquired in a time normally used for one T sat . With the additional T sat ‐dependence information, LOVARS phase maps were produced with a more clearly defined tumor boundary and an estimated 4.3‐fold enhanced contrast‐to‐noise ratio (CNR). We also show that enhancing CNR is achievable by simply averaging the collected images or transforming them using the principal component analysis. Conclusions MeLOVARS enables collection of multiple saturation‐time‐weighted images without extra time, producing a LOVARS phase map with increased CNR. Magn Reson Med 73:488–496, 2015. © 2014 Wiley Periodicals, Inc.