MR Center, Department of Radiology, Medical University of Vienna, Lazarettgasse 14, Vienna, A-1090, Austria.
Eur Radiol. 2011 Jun;21(6):1136-43. doi: 10.1007/s00330-010-2029-7. Epub 2010 Dec 12.
This study compares the performance and the reproducibility of quantitative T2, T2* and the magnetisation transfer ratio (MTR) of articular cartilage at 7T and 3T.
Axial MRI of the patella was performed in 17 knees of healthy volunteers (25.8 ± 5.7 years) at 3T and 7T using a comparable surface coil and whole-body MR systems from the same vendor, side-by-side. Thirteen knee joints were assessed once, and four knee joints were measured three times to assess reproducibility. T2 relaxation was prepared by a multi-echo, spin-echo sequence and T2* relaxation by a multi-echo, gradient-echo sequence. MTR was based on a magnetisation transfer-sensitized, steady-state free precession approach. Statistical analysis-of-variance and coefficient-of-variation (CV) were prepared.
For T2 and T2*, global values were significantly lower at 7T compared with 3T; the zonal evaluation revealed significantly less pronounced stratification at 7T (p < 0.05). MTR provided higher values at 7T (p < 0.05). CV, indicating reproducibility, showed slightly lower values at 7T, but only for T2 and T2*.
Although lower T2 and T2* relaxation times were expected at 7T, the differences in stratification between the field strengths were reported for the first time. The assessment of MT is feasible at 7T, but requires further investigation.
本研究比较了 7T 和 3T 下关节软骨定量 T2、T2*和磁化传递比（MTR）的性能和可重复性。
17 名健康志愿者（25.8±5.7 岁）的髌骨关节进行了轴向 MRI 检查，分别在 3T 和 7T 下使用相同供应商的可比表面线圈和全身 MR 系统进行检查。13 个膝关节进行了一次评估，4 个膝关节进行了三次测量以评估可重复性。T2 弛豫通过多回波、自旋回波序列进行准备，T2*弛豫通过多回波、梯度回波序列进行准备。MTR 基于磁化传递敏感的稳态自由进动方法。准备了方差分析和变异系数（CV）的统计分析。
与 3T 相比，7T 下全局 T2 和 T2值明显更低；区域评估显示 7T 下分层程度明显较低（p<0.05）。7T 时 MTR 提供了更高的值（p<0.05）。表示可重复性的 CV 在 7T 时略低，但仅针对 T2 和 T2。
尽管在 7T 下预计 T2 和 T2*弛豫时间会更低，但本研究首次报道了两种场强之间分层程度的差异。7T 下评估 MT 是可行的，但需要进一步研究。
