Investigate The Accuracy For Absolute Quantification Of Brain Creatine Concentration Using Long TE PRESS Sequence With An External Standard And LCModel

Introduction Creatine(Cr) detected by ~1H-MRS, resonating at 3. 03 ppm and 3.94 ppm chemical shift, represents the quantity of phosphocreatine (PCr) and creatine(Cr) involved in neurones and glial cells. As the storage and transmission of phosphate-bound energy, Cr/PCr plays essential role in energy metabolism. It can undergo phosphorylation-dephosphorylation reaction catalyzed by the enzyme creatine kinase:ADP+PCr←→ATP+Cr. If oxidative phosphorylation cannot be maintained to supply ATP, PCr can provide the phosphate group to ADP to form ATP and reduce the extent of non-oxidative glucose consumption, which can reduce neuronal death mostly due to a delayed decrease of ATP under hypoxic stress and protect the normal brain function against the accumulation of Lactate. Non-invasive detection of brain Cr concentration using ~1H-MRS has an important clinical significance for the diagnosis and treatments of brain diseases related to the change of Cr content. In localized brain MR spectroscopy, the measurement results had been expressed as metabolite ratios for a long period. However, dilemma existed because metabolite ratios were not comparable with quantitative results obtained with biopsy samples and in vitro animal studies. Internal standard such as water have been utilized to acquire Cr concentration, however, this method was also reported to have a number of potential errors, so the measurement result was not accurate. For this reason MR external standard method is preferable. Previously, short echo time (TE) STEAM sequence and short TE PRESS sequence have been used to quantify brain Cr concentration. Concerning signal to noise ratio, PRESS sequence is better than STEAM sequence. The use of short TE has a advantage to investigate the short T2 metabolites, such as glutamate + glutamine (Glx) and myo-inositol (Ins). Cr is a...