Department of Radiology, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
J Magn Reson Imaging. 2010 Mar;31(3):531-7. doi: 10.1002/jmri.22070.
To compare apparent diffusion coefficients (ADCs) with distributed diffusion coefficients (DDCs) in high-grade gliomas.
Twenty patients with high-grade gliomas prospectively underwent diffusion-weighted MRI. Traditional ADC maps were created using b-values of 0 and 1000 s/mm(2). In addition, DDC maps were created by applying the stretched-exponential model using b-values of 0, 1000, 2000, and 4000 s/mm(2). Whole-tumor ADCs and DDCs (in 10(-3) mm(2)/s) were measured and analyzed with a paired t-test, Pearson's correlation coefficient, and the Bland-Altman method.
Tumor ADCs (1.14 +/- 0.26) were significantly lower (P = 0.0001) than DDCs (1.64 +/- 0.71). Tumor ADCs and DDCs were strongly correlated (R = 0.9716; P < 0.0001), but mean bias +/- limits of agreement between tumor ADCs and DDCs was -0.50 +/- 0.90. There was a clear trend toward greater discordance between ADC and DDC at high ADC values.
Under the assumption that the stretched-exponential model provides a more accurate estimate of the average diffusion rate than the mono-exponential model, our results suggest that for a little diffusion attenuation the mono-exponential fit works rather well for quantifying diffusion in high-grade gliomas, whereas it works less well for a greater degree of diffusion attenuation.
比较高级别胶质瘤中的表观扩散系数（ADC）与分布扩散系数（DDC）。
20 例高级别胶质瘤患者前瞻性接受扩散加权 MRI 检查。传统 ADC 图采用 b 值为 0 和 1000 s/mm² 进行绘制。此外，还通过应用拉伸指数模型，采用 b 值为 0、1000、2000 和 4000 s/mm² 绘制 DDC 图。对全肿瘤 ADC 和 DDC（10⁻³mm²/s）进行测量和分析，采用配对 t 检验、皮尔逊相关系数和 Bland-Altman 法。
肿瘤 ADC（1.14±0.26）明显低于 DDC（1.64±0.71）（P=0.0001）。肿瘤 ADC 和 DDC 呈强相关（R=0.9716；P＜0.0001），但肿瘤 ADC 和 DDC 之间的平均偏差±一致性界限为-0.50±0.90。在高 ADC 值时，ADC 与 DDC 之间的不一致性明显增加。
在拉伸指数模型比单指数模型更能准确估计平均扩散率的假设下，我们的结果表明，对于较小的扩散衰减，单指数拟合在量化高级别胶质瘤中的扩散方面效果相当好，而对于较大程度的扩散衰减效果则较差。
