垂体大腺瘤1.5T MR扩散加权成像的参数优化

目的探讨在1.5T MR上应用头线圈进行垂体大腺瘤扩散加权成像（DWI）的可行性,并优化序列参数,探索理想的层厚和b值。方法随机选取15名健康志愿者及15例垂体大腺瘤患者,测定b值分别为300、800、1200s/mm2时的信号强度、背景噪声及垂体瘤的表观扩散系数（ADC）值。比较不同b值时正常垂体的信号强度、质量指数及信噪比的差异;同一b值时垂体大腺瘤平均ADC值的差异。结果 （1）正常垂体DWI图像各b值时的信号强度随b值增加而显著降低（P〈0.01）,而噪声则与b值无关（P〉0.05）;（2）b=800s/mm2时,垂体大腺瘤的平均ADC值为（1.032±0.059）×10^-3mm^2/s,正常垂体平均ADC值为（4.025±0.382）×10^-3mm^2/s,两者差异有统计学意义（P〈0.05）;（3）b=800s/mm^2时,层厚3、4mm对垂体瘤显示评分明显高于2mm（P〈0.05）,层厚4mm时图像伪影比3mm和2mm明显（P〈0.05）。结论 1.5T MR行垂体大腺瘤DWI是可行的。以层厚3mmb值为800s/mm2的图像质量为佳。

Parameters Optimization of Diffusion-weighted Imaging of the Pituitary Macroadenoma at 1.5T MR

Objective To demonstrate the feasibility of DWI in pituitary macroadenoma with head coil on 1.5T system,and to optimize the parameters of sequence,including slice thickness and b-value.Methods Fifteen healthy volunteers and fifteen patients with pituitary macroadenoma were recruited in this study.Signal intensity,background noise and the ADC-value of the pituitary macroadenoma were measured when the b-value was 300,800,1 200 s /mm^2 respectively,compared with the differences of signal intensity,quality index and background noise of the pituitary with the different b-value,difference of mean ADC-value of the pituitary macroadenoma with the same b-value.Results（1） Signal intensity and signal-to-noise,quality index of DWI image of pituitary were different with different b-value,it was de-creasing with the increase of b-value.The difference was significant with different b-value（P〈0.01）,but background noise had no relationship with b-value（P〉 0.05）.（2） The mean ADC-value of the pitui-tary macroadenoma and the pituitary were（1.032 ± 0.059） × 10 ^^-3 mm^2 /s and（4.025 ± 0.382） × 10 ^-3 mm^2 /s with b-value of 800 s /mm^2,comparison of them was showed（P〈 0.05）.（3） The quality index with slice thickness of 3,4 mm with b-value of 800 s /mm2 was higher than that of 2 mm（P 〈0.05）,and the background noise was higher with the slice thickness of 4 mm.Conclusion It is feasible to perform DWI on pituitary macroadenoma with 1.5T MR.The DWI sequence was optimized to acquire enough SNR with the slice thickness of 3 mm and b-value of 800 s /mm^2 general scores for pituitary macroadenoma.