Application of volumetric MR spectroscopic imaging for localization of neocortical epilepsy

Abstract

Purpose The aim of this study was to evaluate volumetric proton magnetic resonance spectroscopic imaging (MRSI) for localization of epileptogenic foci in neocortical epilepsy. Methods Twenty-five subjects reporting seizures considered to be of neocortical origin were recruited to take part in a 3-Tesla MR study that included high-resolution structural MRI and a whole-brain MRSI acquisition. Using a fully-automated MRSI processing protocol, maps for signal-intensity normalized N-Acetylaspartate (NAA), creatine, and choline were created, together with the relative volume fraction of grey-matter, white-matter, and CSF within each MRSI voxel. Analyses were performed using visual observation of the metabolite and metabolite ratio maps; voxel-based calculation of differences in these metabolite maps relative to normal controls; comparison of average grey- and white-matter metabolite values over each lobar volume; and examination of relative left-right asymmetry factors by brain region. Results Data from fourteen subjects were suitable for inclusion in the analysis. Eight subjects had MRI-visible pathologies that were associated with decreases in NAA/Creatine, which extended beyond the volume indicated by the MRI. Five subjects demonstrated no significant metabolic alterations using any of the analysis methods, and one subject had no findings on MRI or MRSI. Conclusions This proof of principle study supports previous evidence that alterations of MR-detected brain metabolites can be detected in tissue areas affected by neocortical seizure activity, while additionally demonstrating advantages of the volumetric MRSI approach.

Effects of tissue susceptibility on brain temperature mapping

“…These studies were carried out under five research protocols, each of which was approved by the institutional human subjects research review committee and with informed consent obtained from all participants. Results using these normal control data have been previously published (Govind et al, 2010; Govind et al, 2012; Maudsley et al, 2009; Maudsley et al, 2010a; Sabati et al, 2015). Subjects were screened to exclude any history of brain disease or injury, substance abuse, or psychiatric condition.…”

Clinical Proton MR Spectroscopy in Central Nervous System Disorders

“…Abnormalities in tNAA concentration and the tNAA/tCr ratio have been useful for detecting injured brain in the seizure onset focus (145)(146)(147)(148)(149). MR spectroscopic imaging measures have also been extended to neurotransmitters, for example, to assess g-aminobutyric patients (142,143).…”

Denoising of MR spectroscopic imaging data using statistical selection of principal components

“…These data were acquired using a spin-echo acquisition with two-dimensional phase encoding, echo-planar readout in the k y -time dimensions, frequency-selective water suppression and TR/TE = 1551/17.6. Sequence details have been provided elsewhere [25-27]. The acquisition included a water-reference dataset obtained in an interleaved manner with identical spatial parameters as the metabolite MRSI.…”

“…The acquisition included a water-reference dataset obtained in an interleaved manner with identical spatial parameters as the metabolite MRSI. MRSI acquisition was preceded by an inversion-recovery preparation, with TI = 198 ms, to suppress signal from subcutaneous lipids [25, 27]. A T1-weighted image (MPRAGE, Magnetization Prepared Rapid Gradient Echo) at 1-mm resolution (TR/TE/TI = 2300/2.4/930 ms) was also acquired for each study.…”