Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
Korean J Radiol. 2010 Jan-Feb;11(1):54-9. doi: 10.3348/kjr.2010.11.1.54. Epub 2009 Dec 28.
We wanted to evaluate the effect of the number of diffusion-sensitizing gradient directions on the image quality for evaluating myocardial anisotropy and fiber tracking by using in vitro diffusion tensor MR imaging (DT-MRI).
The DT-MR images, using a SENSE-based echoplanar imaging technique, were acquired from ten excised porcine hearts by using a 3T MR scanner. With a b-value of 800 s/mm(2), the diffusion tensor images were obtained for 6, 15 and 32 diffusion-sensitizing gradient directions at the midventricular level. The number of tracked fibers, the fractional anisotropy (FA), and the length of the tracked fibers were measured for the quantitative analysis. Two radiologists assessed the image quality of the fiber tractography for the qualitative analysis.
By increasing the number of diffusion-sensitizing gradient directions from 6 to 15, and then to 32, the FA and standard deviation were significantly reduced (p < 0.01), and the number of tracked fibers and the length of the tracked fibers were significantly increased (p < 0.01). The image quality of the fiber tractography was significantly increased with the increased number of diffusion-sensitizing gradient directions (p < 0.01).
The image quality of in vitro DT-MRI is significantly improved as the number of diffusion-sensitizing gradient directions is increased.
我们通过体外扩散张量磁共振成像（DT-MRI）评估了扩散敏感梯度方向的数量对心肌各向异性和纤维追踪图像质量的影响。
在 3T MR 扫描仪上使用基于 SENSE 的平面回波成像技术，从 10 个离体猪心获取 DT-MRI 图像。b 值为 800 s/mm(2)时，在心脏中层水平获取 6、15 和 32 个扩散敏感梯度方向的扩散张量图像。用于定量分析的参数包括：追踪纤维的数量、各向异性分数（FA）和追踪纤维的长度。两位放射科医生对纤维束示踪的图像质量进行了定性评估。
随着扩散敏感梯度方向数量从 6 增加到 15，再增加到 32，FA 和标准差显著降低（p < 0.01），追踪纤维的数量和追踪纤维的长度显著增加（p < 0.01）。随着扩散敏感梯度方向数量的增加，纤维束示踪的图像质量显著提高（p < 0.01）。
随着扩散敏感梯度方向数量的增加，体外 DT-MRI 的图像质量得到显著改善。
