Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota.
Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota.
Magn Reson Med. 2019 Apr;81(4):2624-2631. doi: 10.1002/mrm.27563. Epub 2018 Nov 2.
Correction of Nyquist ghosts for single-shot spin-echo EPI using the standard 3-line navigator often fails in breast DWI because of incomplete fat suppression, respiration, and greater B inhomogeneity. The purpose of this work is to compare the performance of the 3-line navigator with 4 data-driven methods termed "referenceless methods," including 2 previously proposed in literature, 1 introduced in this work, and finally a combination of all 3, in breast DWI.
Breast DWI was acquired for 41 patients with SS SE-EPI. Raw data was corrected offline with the standard 3-line navigator and 4 referenceless methods, which modeled the ghost as a linear phase error and minimized 3 unique cost functions as well as the median solution of all 3. Ghost levels were evaluated based on the signal intensity in the background region, defined by a mask auto-generated from a T -weighted anatomical image. Ghost intensity measurements were fit to a linear mixed model including ghost correction method and b-value as covariates.
All 4 referenceless methods outperformed the standard 3-line navigator with statistical significance at all 4 b-values tested (b = 0, 100, 600, and 800 s/mm ).
Referenceless methods provide a robust way to reduce Nyquist ghosts in breast DWI without the need for any additional calibration scan.
在单次激发自旋回波 EPI 中使用标准的 3 线导航器校正奈奎斯特鬼影，由于不完全的脂肪抑制、呼吸和更大的 B 不均匀性，在乳腺 DWI 中经常失败。本研究的目的是比较 3 线导航器与 4 种称为“无参考方法”的数据驱动方法的性能，包括文献中之前提出的 2 种、本研究中提出的 1 种，以及最终的 3 种方法的组合，在乳腺 DWI 中的性能。
对 41 例 SS SE-EPI 患者进行乳腺 DWI 采集。原始数据在离线时使用标准的 3 线导航器和 4 种无参考方法进行校正，这些方法将鬼影建模为线性相位误差，并最小化 3 个独特的代价函数以及所有 3 个的中位数解。根据背景区域（由 T1 加权解剖图像自动生成的蒙版定义）的信号强度评估鬼影水平。鬼影强度测量值拟合到包含鬼影校正方法和 b 值作为协变量的线性混合模型。
所有 4 种无参考方法在所有 4 个测试的 b 值（b=0、100、600 和 800 s/mm）上均显著优于标准 3 线导航器。
无参考方法为减少乳腺 DWI 中的奈奎斯特鬼影提供了一种稳健的方法，无需任何额外的校准扫描。
