Annu Int Conf IEEE Eng Med Biol Soc. 2021 Nov;2021:4023-4026. doi: 10.1109/EMBC46164.2021.9630596.
Diffusion weighted imaging is a widely used imaging technique for the assessment of white matter using tractography. Nevertheless, due to practical constraints such as limited acquisition times, differences in scanning methods and physical artifacts, these images must be processed by image correction algorithms in order to produce reliable results. State-of-the art susceptibility correction algorithms such as FSL's TOPUP algorithm typically requires at least two images acquired with no diffusion encoding (b=0) in the regular and reverse phase encoding directions, commonly known as double-blip acquisitions, in order to calculate an undistorted volume. Since not all imaging protocols include a double-blip acquisition, they cannot take advantage of these state-of-the art distortion correction algorithms. A new approach based on a Synthetic b-0 Distortion Correction (Synb0-DisCo) has been tested with favourable results. Synb0-DisCo has proven to reduce variation in diffusion modeling creating a synthetic b-0 image to complement the single phase encoding b0 image. In this study, we aim to assess if there are any significant differences in Synb0-DisCo's efficacy resulting from different b-values. To observe critical metrics in the performance of susceptibility correction algorithms we use a 20 healthy subject database from project larynx to create four image sets containing: raw images, single phase encoding eddy correction, double phase encoding eddy correction and one single phase encoding plus a synthetic Synb0-DisCo image eddy correction. From this four image sets we then obtained the mean squared error (MSE) and mutual information (MI). We observed a diminished mean in the MSE, along a smaller dispersion, in the raw image set (Mean: 0.0306; C.I.[0.0369,0.024]) in comparison to the Synb0 image set (Mean: 0.0130; C.I.[0.0194, 0.0067]) We also observe a shift in the MSE depending on the b-value, where b-0 incurs the least MSE which does not occur in b-1000 and b-2000. This effect is lessened in the Synb0 image set. In absence of double phase encoding b-0 image, Synb0-DisCo proves to be a reliable algorithm to improve susceptibility distortion correction.
弥散加权成像是一种广泛应用于白质评估的成像技术，通过轨迹追踪进行。然而，由于实际限制，如有限的采集时间、扫描方法的差异和物理伪影，这些图像必须通过图像校正算法进行处理，以产生可靠的结果。目前的基于磁化率的校正算法，如 FSL 的 TOPUP 算法，通常需要至少两幅在常规和反转相位编码方向上没有弥散编码（b=0）的图像，通常称为双回波采集，以便计算未失真的体积。由于并非所有成像方案都包括双回波采集，因此它们无法利用这些最先进的失真校正算法。一种新的基于合成 b0 失真校正（Synb0-DisCo）的方法已经得到了测试，并取得了良好的效果。Synb0-DisCo 已被证明可以减少弥散建模中的变化，创建一个合成的 b0 图像来补充单相位编码 b0 图像。在这项研究中，我们旨在评估不同 b 值对 Synb0-DisCo 功效的影响是否有显著差异。为了观察磁化率校正算法性能的关键指标，我们使用来自 larynx 项目的 20 个健康受试者数据库创建了四个图像集，其中包含：原始图像、单相位编码涡流校正、双相位编码涡流校正和一个单相位编码加一个合成的 Synb0-DisCo 图像涡流校正。然后，我们从这四个图像集中获得了均方误差（MSE）和互信息（MI）。我们观察到，在原始图像集（Mean：0.0306；C.I. [0.0369，0.024]）中，MSE 的均值降低，离散度减小，而在 Synb0 图像集（Mean：0.0130；C.I. [0.0194，0.0067]）中，MSE 的均值降低，离散度减小。我们还观察到 MSE 取决于 b 值的变化，其中 b0 导致的 MSE 最小，而在 b-1000 和 b-2000 中则不会发生这种情况。这种效应在 Synb0 图像集中减弱。在没有双相位编码 b0 图像的情况下，Synb0-DisCo 证明是一种可靠的算法，可以改善磁化率失真校正。
