兔肝VX2瘤活体二维多体素~1H-MRS的成像技术

Technology of in vivo twodimension multi-voxel 1~H magnetic resonance spectroscopy for rabbit liver VX2 tumor

目的:探讨兔肝VX2瘤活体二维多体素~1H-MRS(2D^1H-MRS)最佳成像技术.方法:经腹腔瘤块种植法行肝内VX2瘤种植成功的新西兰大白兔8只,2-4 wk内采用1.5 T磁共振仪行常规MRI平扫及活体2D^1H-MRS检查.采用膝关节线圈,在其他参数不变的条件下分别用不同的TR、TE和NEX进行活体2D^1H-MRS扫描,观察2D^1H-MRS谱图,以波谱图基线情况和信噪比为指标进行统计学分析.结果:在成功获得的可析性2D^1H-MRS谱图上最多可看到6个主要的代谢物波峰:脂质的甲基峰(Lipl)、脂质的亚甲基峰(Lip2)、含双碳键的脂质亚甲基峰(Lip3),谷氨酰胺和谷氨酸复合物(Glx),胆碱化合物(Cho),糖原和葡萄糖复合物(Glyu).TR逐渐延长(1000 ms、2000 ms、3000 ms)基线情况和信噪比无显著性差异.TE=30 ms与TE=144 ms的基线情况未见明显差异,除了Glx的信噪比在TE=30 ms时稍高(1.95±0.36 vs 1.24±0.26,P<0.05)以外,其他几种代谢物的信噪比在不同TE无显著性差异.激励次数(number of exciration,NEX)增大(4次、8次、16次),谱图基线差别较大(x^2 =10.000,P<0.01),主要代谢物信噪比均随着NEX的增大而增大.NEX=16次时基线最平稳,信噪比最高.结论:利用1.5 T磁共振仪进行兔肝VX2瘤活体2D^1H-MRS检查可行,为肝脏2D^1H-MRS的临床应用提供了基础.通过加强制动、预扫描使匀场和抑水效果达到水峰FWHM≤10Hz,WS≥98%、使用膝关节线圈、选择TR =1000 ms、TE=30 ms和较大的NEX(16次)等有利于成功获得较高质量的可析性波谱图.

AIM：To investigate the best techniques of in vivo two-dimension multi-voxel 1H magnetic resonance spectroscopy（2D 1^H-MRS）for rabbit liver VX2 tumor. METHODS：The liver of 8 New Zealand white rabbits was implanted directly and respectively with VX2 tumor lump after abdominal cavity was opened.2D 1^H-MRS acquisition in vivo and unenhanced MRI was performed respectively from the 2nd week to 4th week after VX2 tumor was implanted.With knee coil,in vivo 2D 1^H- MRS acquisitions were performed respectively with different TR,different TE and different NEX at 1.5 T MR scanner when other parameters were the same.The distinction between groups was analyzed by SPSS11.0 with baseline and signal-noise ratio（SNR）. RESULTS：From the qualified MRS spectrum, there were up to 6 peaks which could be identified：methyl lipids（Lip1）,methylene lipids （Lip2）,methylene lipids with double carbon bond（Lip3）,glutamine and glutamate complex （Glx）,Choline（Cho）,and glycogen and glucose complex Glyu）.Baseline and SNR had no significant differences between TR=1000 ms,2000 ms and 3000ms.Baseline had no significant difference between TE=30 ms and 144 ms.Except that SNR of Glx with 30 ms in TE was higher than that with 144ms in TE（1.95±0.36 vs 1.24±0.26,P〈0.05）,SNR of other metabolites were similar.With NEX increasing,the distinctions of baseline between NEX=4,8 and 16 were significant（Х^2=10.000,P〈0.01）.SNR of all metabolites increased when NEX was increased gradually.Both of baseline and SNR were the best when NEX was 16. CONCLUSION：It＇s practical of in vivo two- dimension multi-voxel 1^H-MRS on the rabbit liver VX2 tumor by a 1.5 T MR scanner.Immobilization,pre-scan（reaching FWHM≤10 Hz and WS≥98%）,knee coil,TR=1000 ms,TE=30 ms and NEX=16 may be the best to acquire highly qualified spectra.