Premium
Correlation chemical shift imaging with low‐power adiabatic pulses and constant‐density spiral trajectories
Author(s) -
Andronesi Ovidiu C.,
Gagoski Borjan A.,
Adalsteinsson Elfar,
Sorensen A. Gregory
Publication year - 2012
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.1730
Subject(s) - adiabatic process , nuclear magnetic resonance , spectroscopy , physics , flip angle , spiral (railway) , anisotropy , chemistry , optics , mathematics , mathematical analysis , magnetic resonance imaging , medicine , quantum mechanics , radiology , thermodynamics
In this work we introduce the concept of correlation chemical shift imaging (CCSI). Novel CCSI pulse sequences are demonstrated on clinical scanners for two‐dimensional Correlation Spectroscopy (COSY) and Total Correlation Spectroscopy (TOCSY) imaging experiments. To date there has been limited progress reported towards a feasible and robust multivoxel 2D COSY. Localized 2D TOCSY imaging is shown for the first time in this work. Excitation with adiabatic GOIA‐W(16,4) pulses (Gradient Offset Independent Adiabaticity Wurst modulation) provides minimal chemical shift displacement error, reduced lipid contamination from subcutaneous fat, uniform optimal flip angles, and efficient mixing for coupled spins, while enabling short repetition times due to low power requirements. Constant‐density spiral readout trajectories are used to acquire simultaneously two spatial dimensions and f 2 frequency dimension in ( k x , k y , t 2 ) space in order to speed up data collection, while f 1 frequency dimension is encoded by consecutive time increments of t 1 in ( k x , k y , t 1 , t 2 ) space. The efficient spiral sampling of the k ‐space enables the acquisition of a single‐slice 2D COSY dataset with an 8 × 8 matrix in 8:32 min on 3 T clinical scanners, which makes it feasible for in vivo studies on human subjects. Here we present the first results obtained on phantoms, human volunteers and patients with brain tumors. The patient data obtained by us represent the first clinical demonstration of a feasible and robust multivoxel 2D COSY. Compared to the 2D J‐resolved method, 2D COSY and TOCSY provide increased spectral dispersion which scales up with increasing main magnetic field strength and may have improved ability to unambiguously identify overlapping metabolites. It is expected that the new developments presented in this work will facilitate in vivo application of 2D chemical shift correlation MRS in basic science and clinical studies. Copyright © 2011 John Wiley & Sons, Ltd.