模型模拟修改部分扫描参数加速MR扫描的方法可行性探讨

Feasibility of accelerating MR scan by modifying part of scanning parameters：a phantom simulation study

目的：探讨修改部分扫描参数加速MR扫描的方法。方法先以仪器制造商提供的颈部软组织横轴位（Tra）自旋回波（SE）平扫T1加权、 T2加权序列扫描Philips Achieva 1．5T MRI系统的质量控制模型；然后在数据采集界面的“Geometry、 Contrast”等选项中修改视野（FOV）/矩阵（Matrix）/体素（Voxel）、并行采集（SENSE）、最小重复时间（Min．TR）、回波时间（TE）、快速自旋回波因子（TSE factor）等参数，并分别对模型相同区域进行扫描；比较参数修改前、后相应序列的总扫描时间（TSD）、图像视觉效果，并以Tra图像ROI内信噪比（SNR）、非均匀性（NU）和X轴方向profile曲线评价图像质量；采用SPSS17．0软件对相应序列定量数据进行配对t检验分析。结果参数修改后T1加权、 T2加权序列的TSD比修改前分别减少了38．5s（25．56%）和40．0s（22．22%）。目测相应序列均匀区、线性区Tra图像和profile曲线在扫描参数修改前、后没有差异。参数修改前T1加权、 T2加权的SNR均值分别为77．89、79．58，修改后为83．17、81．79，较修改前均有上升，但差异无统计学意义（t=-1．891， P=0．199； t=-1．474， P=0．278）；参数修改前T1加权、 T2加权的NU均值分别为6．99、6．99，修改后为6．03、6．89，较修改前均有下降，但差异无统计学意义（t=0．802， P=0．507； t=0．168， P=0．882）。结论模型模拟研究显示，合理修改扫描参数可以在确保图像质量的同时加速MR扫描。

Objective To investigate the feasibility of accelerating MR scan by modifying the scanning parameters. Methods First, the spine cho（SE） T1-weighted and T2-weighted sequences of neck soft tissue were used to scan the transverse （ Tra ） slices of the special quality control phantom of the Philips Achieva 1.5T system. The FOV/Matrix/Voxel, SENSE, Min.TR, TE, and TSE factor were modified in the “Geometry, Contrast” mode of the data acquisition interface to accelerate the scanning speed. The phantom was scanned at the same time the scanning parameters were modified. Finally, the total scan duration （ TSD ） of the corresponding sequences was compared . The signal-to-noise ratio （ SNR ） , non-uniformity（NU） in the ROI, and profile curve in the X-direction of the Tra images were used to evaluate image quality before and after the scanning parameters were modified. Paired t-test was used to analyze the quantitative data. Results Approximately 38.5 s（25.56%） and 40.0 s（22.22%）were saved corresponded to the T1-weighted and T2-weighted sequences, respectively, after the scanning parameters were modified. Visual differences in the images and profile curves of the corresponding sequences were not found between before and after the modification of scanning parameters. The mean SNRs of the T1-weighted and T2-weighted sequences increased slightly after the modification , but the differences were not significant （t=-1.891, P=0.199; t=-1.474, P=0.278）. The mean NUs slightly decreased after the modification, but the differences were also not significant （t=0.802, P=0.507; t=0.168, P=0.882）. Conclusion The phantom test showed that the MR scan speed was accelerated and image quality was ensured by modifying the scanning parameters.