Citrate Level Measurement
Proton MRS were acquired using a single-voxel point-resolved
spectroscopy (PRESS) with a short echo time (TE) of 35 milliseconds, a
repetition time (TR) of 1.5 seconds, and 128 signal averages were used
for all acquisitions(14). The total acquisition time, which included
scanner adjustments, was less than five minutes per spectrum. All
spectra were processed with fully automated LCModel (Stephen Provencher
Inc., Oakville, Ontario, Canada, LCModel Version 6.3-1L) software and
citrate was quantified as previously described(4, 15). MRS data was
acquired prior to contrast injections using a 1.5T MR System (Sign LX;
EG Healthcare). Patients aged less than 5 years were imaged under
general anesthesia. Single voxel short TE was used to obtain signals
with minimal signal loss due to T2 signal decay of metabolites.
T2-weighed fast spin-echo, fluid-attenuated inversion recovery (FLAIR),
and T1-weighed FLAIR magnetic resonance (MR) images were acquired in all
cases and reviewed to determine the extent of the lesion prior to
selecting the region of interest. This region was documented in three
MRIs and reviewed to ensure that no partial volume for normal appearing
tissue was enclosed. Sizes and shaped of this region were adjusted to
the lesion sizes and typically varied from 5-10cm3(Figure 1).