Metabolic Changes on Occipital Cortex during Visual Stimulation with Functional MR Imaging and 1H Spectroscopy

ABSTRACT

PURPOSE: The purpose of this study was aimed to evaluate BOLD(blood oxygen level dependent) contrast fMRI(function MR imaging) in the occipital lobe and to compare with the metabolic changes based on 1H MRS(MR spectroscopy) and MRSI(MR spectroscopic imaging) before and after visual stimulation MATERIALS AND METHODS: Healthy human volunteers(eight males and two females with 24-30 year age) participated in this study. All of the BOLD fMRI were acquired on a 1.5T MR with EPI during supervised visual stimulation in the occipital lobe. The red flicker with 8Hz was used for visual stimulation. After imaging acquisition, the MR images were transferred into unix workstation and processed with home made analysis software based on the correlation coefficient method. Proton MRS data sets were acquired from the same location based on the activation map. MRSI(magnetic resonance spectroscopic imaging) was also acquired to analyze the lactate changes before and after stimulation. RESULTS: The activation maps were successfully produced by BOLD effect due to visual stimulation. NAA(N-acetyle aspartate)/Cr(creatine) ratio varied only from 1.790.28 to 1.880.20 in activation area before and after stimulation. However, the signal intensity of lactate was elevated 9.484.38times higher than before activation. Lactate metabolite images were consistent with the activation maps. CONCLUSION: The BOLD contrast fMRI is enough sensitive to detect the activated area in human brain during the visual stimulation. Lactate metabolite map presents the evidence of lactate elevation on the same area of activation.