应用磁共振扰相梯度双回波鉴别急性脑实质出血和钙化的定量研究

Quantitative study of differential diagnosis between acute cerebral hemorrhage and calcification by using spoiled GRE T2 dual echo MRI

目的 研究磁共振扰相梯度回波诊断与鉴别诊断急性出血和钙化的定量指标 ,总结急性脑出血在双回波T2 加权像上影像表现 ,探讨其影像表现的产生机制。方法 以CT作为金标准 ,对已确诊急性脑出血的 8例 13个病灶 (A组 )和颅内钙化 5例 14个病灶 (B组 )进行磁共振FLASHT2双回波 (15 /3 5ms)检查。总结其MR的表现。测量不同TE情况下MR图像上低信号区面积 ,计算低信号面积增大率。测量不同相位编码方向情况下 ,MR低信号区的前后径与左右径。结果 钙化和出血病灶的双回波上低信号区域面积增大率差异有显著性 (P <0 .0 1) ,急性脑出血病灶的低信号区面积增大率 (0 .44 ,0 .3 4～ 0 .49)明显大于钙化灶的增大率 (0 .11,-0 .0 6～ 0 .0 9)。TE =15ms出血灶和钙化灶以及TE =3 5ms钙化灶低信号区的前后径和左右径在改变相位编码方向时差异无显著性 (P >0 .0 5 )。TE =3 5ms时 ,出血灶低信号区前后径 (左右径 )在相位编码方向为前后 (左右 )时比相位编码方向为左右 (前后 )时增大 (P <0 .0 5 )。结论 依据扰相梯度T2 双回波上低信号区域面积增大率(面积法 )和低信号区前后径和左右径在不同相位编码方向上的变化情况 (径线法 )可以鉴别急性脑出血和钙化 ,定量鉴别的物理基础为出血与钙化的磁感应性不同 。

Objective To study a rapid and quantitative method for the diagnosis of cerebral hemorrhage at superacute stage by MRI, and to define the quantitative criterion of the differential diagnosis between acute cerebral hemorrhage and calcification by using FLASH T2 dual-echo magnetic resonance imaging. Methods FLASH T2 dual echo imaging with TE of 15ms and 35ms was performed in 8 cases (13 lesions, Group A) of acute cerebral hematoma and 5 cases (14 lesions, Group B) of calcification. The final diagnosis of each case was proved by CT which was taken as golden standard. The measurement was performed under the chosen window width and center. The ratio of the dark area at different TE values was compared between Group A and B, and the anterior-posterior (A-P) and the right-left (R-L) diameter of the dark area under different phase encoding directions was also measured and compared between the two groups. Results The enlargement ratio of the dark area at different TE values was statistically different between group A and B ( P <0.01), and the mean value of Group A (0.44, 0.34-0.49) was greater than that of Group B (0.11,-0.06-0.09). The A-P or L-R diameter under different phase-encoding direction was not changed significantly in Group A with TE of 15 ms and Group B with both TE values ( P >0.05), while the diameter under different phase-encoding direction was significantly different in Group A with TE of 35 ms ( P <0.05). Conclusion The quantitatively differential diagnosis between acute cerebral hematoma and calcification is available by the ratio of dark area at different TE values, or by the changes of A-P/L-R diameter under different phase-encoding directions. The susceptibility difference between hematoma and the brain parenchyma should be greater than that between calcification and the brain parenchyma, which should be the biophysical basis for the quantitative differential diagnosis.