长回波时间的点解析波谱序列外标准结合线性拟合模型定量检测脑肌酸浓度准确性的实验研究

Experimental investigation of the accuracy for absolute quantification of brain creatine concentration using long time echo point resolved spectroscopy sequence with an external standard and linear combination of model spectra

目的探讨长回波时间（TE）的点解析波谱序列（PRESS）外标准和线性拟合模型（LCModel）定量检测活体脑肌酸（Cr）浓度的准确性。方法10头2周龄猪及1个外标准模型用于本次实验。氢质子MR波谱（^1H—MRS）实验采用GE 1．5TMR扫描仪及标准正交头线圈。感兴趣区大小为2cm×2cm×2cm，分别定位于动物脑和外标准溶液。PRESS序列按TE135ms，TR1500ms，128次扫描，获得感兴趣区Cr的波谱数据，然后用LCModel分析活体脑Cr浓度。每只动物做完MRS检查后即刻处死，用高效液相色谱方法（HPLC）分析离体脑Cr浓度。采用配对样本t检验比较活体和离体检测结果的差别。结果^1H—MRS测定的活体脑Cr浓度为（9．37±0．14）mmol／kg，HPLC测定的离体脑Cr浓度为（8．91±0．13）mmol／kg，两种方法的检测结果差异无统计学意义（t=9．038，P=0．491）。结论长TE的PRESS序列外标准结合LCModel可以准确无创地定量检测活体脑Cr浓度。

Objective To investigate the accuracy for absolute quantification of brain creatine （Cr） concentration using long time echo （TE） point resolved spectroscopy （PRESS） sequence performed with an external standard and postprocessed with the linear combination of model spectra （ LCModel ）. Methods Ten swine （3. 1 ± 0. 6 kg） and an external standard phantom containing detectable compounds of known concentration were investigated in this study by using 1.5 T GE Signa scanner and a standard head coil. The single-voxel proton magnetic resonance spectroscopy （^1H-MRS） data were acquired from the two ROIs （2 cm ×2 cm ×2 cm） placed in swine brain and external standard solution using PRESS sequence with TE 135 ms, TR 1500 ms, and 128 scan averages. The in vivo quantification of Cr was accomplished by LCModel. After ^1H-MRS examination, each animal was sacrificed immediately. In vitro Cr concentration was analyzed by high performance liquid chromatography （ HPLC ）. Results In the ^1H-MRS group, the Cr concentration was （9. 37 ± 0. 14）mmol/kg. In the HPLC group, the Cr concentration was （8.91 ± 0. 13）mmol/kg. Good agreement was obtained between these two methods （t = 9.038, P = 0.491 ）. Conclusion The long echo time PRESS sequence performed with an external standard and processed with LCModel is proven to be an accurate technique to detect the in vivo brain Cr concentration.