Comparison of Cerebral Occiptal Gray and Parietal White Matter Metabolite Differences Using PRESS and STEAM at Different Echo Times

　　　　　背景：以不同參數與脈衝波序研究人類腦部不同部位新陳代謝化學物質之文獻不 多。本研究目的是以不同脈衝波序度研究國人腦部灰質與白質新陳代謝化學物質之比值。 方法：利用GE Signa 1.5T的磁振掃描儀和Single Voxel定位磁振光譜以不同脈衝波序 PRESS和STEAM來探測正常國人大腦頂葉白質與枕葉灰質生化代謝物之比值。 結果：各類代謝物N-acetyl aspartate Creatine（Cr）、Choline/Cr和Myo-inositol/Cr之比 值在大腦灰質與白質之差異在統計學有意義。在同一個部位，使用不同的回音取訊號時間（TE 或echo time），其比值之差異在統計學上也有意義。 結論：新陳代謝物之比值差異，會因探測腦部部位不同有差異，所用TE不同也有所差 異。故爾後對氫質子磁振光譜之代謝物比值要小心判讀，並注意取訊號之各項參數。吾輩尤 其要注意的是所探測的是各類代謝物的比值而非各代謝物的絕對濃度。
　　　　　Background: Reports regarding the differences in metabolite ratios with different echo times (TEs) at various brain regions are rare. The purpose of this study is to investigate in Chinese the cerebral metabolite ratios in gray matter (GM) and white matter (WM) using both STEAM and PRESS techniques at TEs of 30 ms and 136 ms, respectively. Materials and Methods: Using GE Signa 1.5 T Scanner with STEAM and PRESS sequences, automated single voxel localized proton magnetic resonance spectroscopy (□□H-MRS) were applied to identify the metabolite ratio differences in cerebral parietal white and occipital gray matter of healthy volunteers. Results: Metabolite ratios between GM and WM were significantly different in N-acetyl aspartate/creatine(Cr), choline/Cr and myo-inositol/Cr. There were also significant differences in metabolite ratios when different echo times were applied. Conclusion: Reliable metabolite ratios at different brain regions can be obtained using automated data acquisition and spectral processing in single voxel localized 1H-MRS. This technique may remove user-dependent bias and provide more efficient and consistent ways to analyze the spectral data. However, one must be careful in interpreting spectroscopic data based on different regions and acquisition parameters.