An improved PSF mapping method for EPI distortion correction in human brain at ultra high field (7T)
An improved PSF mapping method for EPI distortion correction in human brain at ultra high field (7T)
复制标题
DOI：
10.1007/s10334-011-0251-1
复制
发表时间：
2011-06-01
影响因子：
2.3
通讯作者：
Cho, Zang-Hee
中科院分区：
文献类型：
--
作者：
Chung, Jun-Young;In, Myung-Ho;Cho, Zang-Hee
为了进一步提高点扩散函数（PSF）映射方法的质量和鲁棒性，以高保真度全自动、准确地校正7特斯拉等超高场下EPI中的几何畸变。在7特斯拉下获得了体模和人脑活体测量中的常规梯度回波EPI和相应的PSF参考数据。为了准确地确定和校正几何畸变，即在外围区域中，该方法计算畸变相位编码维度而不是非畸变自旋包裹编码维度中的局部移位。将所提出的方法的结果与最初演示的结果进行比较（Zaitsev 等人 Magn Reson Med (2004) 52:1156-1166)。结果表明，所提出的方法允许以高精度测量和校正 EPI 中的几何畸变，并减少残余模糊。此外，该方法还可以防止PSF重影伪影引起的移位图错误。通过所提出的改进，可以实现更精确的像素移位和模糊的映射和校正。由多次 PSF 采集中的 PSF 重影伪影（例如，参考扫描期间的小运动）引起的移位图中的误差不会影响改进的移位估计方法。
To further improve the quality and robustness of the point-spread function (PSF) mapping method for fully automatic and accurate correction of geometric distortions in EPI at ultra high field such as 7 Tesla with high fidelity.Conventional gradient-echo EPI and corresponding PSF reference data in phantoms and in in vivo measurements of the human brain were acquired at 7 Tesla. To accurately determine and correct geometric distortions, i.e., in peripheral areas, the method calculates the local shift in the distorted phase-encoding dimension instead of the non-distorted spin-wrap encoding dimension. The results of the proposed method are compared with those originally demonstrated (Zaitsev et al. Magn Reson Med (2004) 52:1156-1166).The results show that the proposed method allows measurement and correction of the geometric distortions in EPI with high accuracy, and reduction of residual blurring. In addition, this method prevents errors in the shift map induced by PSF-ghost artifacts.More precise mapping and correction of pixel shifts and blurring is accomplished with the proposed improvements. Errors in the shift map that are caused by PSF-ghost artifacts in the multi-shot PSF acquisition, e.g., from small motion during the reference scan, do not affect the improved shift estimation method.