title: Adiabatic localized correlation spectroscopy (AL-COSY): application in muscle and brain.
abstract: OBJECTIVE
  To describe an enhanced version of a localized correlation spectroscopy (L-COSY) by introducing adiabatic radiofrequency (RF) pulses for localization in two dimensions. Adiabatic pulses will improve slice selection profile and reduce chemical shift artifacts. Optimized Mao and adiabatic hyperbolic secant pulses are tested in vivo.
  
  
  METHODS
  Region of interest is localized by a 90° nonselective adiabatic RF pulse followed by two pairs of adiabatic RF pulses and a terminal 90° RF sinc pulse. Slice profiles for both refocusing pulses and chemical shift artifacts are measured in a water-oil phantom for L-COSY and AL-COSY. In vivo results of both COSY sequences are shown from muscle and brain on a 3 Tesla (T) scanner.
  
  
  RESULTS
  Chemical shift artifacts were reduced with AL-COSY compared with L-COSY. Slice profiles of adiabatic pulses were found to be sharper and more symmetrical than those of traditional Mao pulses. One-dimensional (1D) phantom studies showed longer T2 values using AL-COSY sequence. Comparison of 2D spectra obtained revealed spectroscopic peak volume improvements in AL-COSY and less residual water. In vivo 1D comparison showed more inphase and sharper peaks in AL-COSY spectrum.
  
  
  CONCLUSIONS
  The AL-COSY sequence is an improved sequence due to sharper slice selection profiles, reduction of chemical shift artifacts, peak volume improvements in 2D techniques, and less J-modulation.
authors: Center for Clinical Spectroscopy, Department of Radiology, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. saad.ramadan@gmail.com
authors: Saadallah
authors: S
authors: Ramadan
authors: Carolyn E
authors: CE
authors: Mountford