Dr. Dong-Hoon Lee, Research Fellow / MRI Physicist, Faculty of Health Sciences and Brain & Mind Centre, The University of Sydney, Australia

Speech Title: Creatine Chemical Exchange Saturation Transfer Imaging in the Epileptic Seizure Rat Models

Abstract: Creatine (Cr) plays a major role in the storage and transmission of phosphate-bound energy. Therefore, evaluating of creatine level changes are important studies in the clinic to estimate the brain energy metabolism. The purpose of this study to demonstrate the feasibility of quantitative and qualitative mapping of creatine using chemical exchange saturation transfer (CrCEST) technique in the epileptic seizure rats. All experimental investigations were performed as a function of time, before and after epilepsy, and the signal correlation analysis between CrCEST and PCr and total Cr (tCr; PCr+Cr) concentration using 1H magnetic resonance spectroscopy (1H MRS) was also investigated. The epileptic seizure was induced in five male Wistar rats by intraperitoneal injection of kainic acid (KA). CEST and 1H MRS data were obtained using a 7.0 T Bruker scanner at different time points (pre KA injection, 3h and 5h after KA injection). CrCEST signals in the hippocampal regions were quantitatively evaluated using the magnetization transfer ratio (MTR) asymmetry with B0, and B1 corrected CEST data. 1H MRS spectra were analysed with a fully blind spectral process using Linear Combination Model software (LCModel) with a simulated basis set. For the correlation analysis between the CrCEST signals and PCr and tCr concentrations from 1H MRS, Spearman’s rank correlation coefficient (r) and p values were calculated. Measured CrCEST signals were exhibited significant differences between before and after KA injection. The CrCEST signals showed significant correlations with PCr values at each time points (all |r| > 0.59; p < 0.05; no significant correlations found from the results between CrCEST signals and tCr values (all |r| < 0.22; p > 0.05). The application of CrCEST imaging to epilepsy showed the significant image contrasts as a function of time of onset of epilepsy. The overall results of the temporal evolution of the signal changes from CrCEST were clearly indicated, which implies that CrCEST imaging can be a useful technique to estimate the diagnosis of epilepsy and further prognosis assessment.

Keywords: creatine, chemical exchange saturation transfer (CEST), epilepsy, magnetic resonance spectroscopy (MRS)