Department of Radiological Science, Shizuoka College of Medicalcare Science.
Magn Reson Med Sci. 2021 Dec 1;20(4):325-337. doi: 10.2463/mrms.mp.2020-0044. Epub 2020 Oct 16.
Our purpose was to assess our proposed new synthetic MRI (synMRI) technique, combined with T-based water suppression (Twsup), to reduce cerebral spinal fluid (CSF)-partial volume effects (PVEs). These PVEs are problematic in the T-weighted fluid-attenuation inversion recovery (FLAIR) images obtained by conventional synMRI techniques.
Our Twsup was achieved by subtracting additionally acquired long TE spin echo (SE) images of water signals dominant from the originally acquired images after T decay correction and a masking on the long TE image using the water volume (V) map to preserve tissue SNR, followed by quantitative mapping and then calculation of the synthetic images. A simulation study based on a two-compartment model including tissue and water in a voxel and a volunteer MR study were performed to assess our proposed method. Parameters of long TE and a threshold value in the masking were assessed and optimized experimentally. Quantitative parameter maps of standard and with Twsup were generated, then wsup-synthetic FLAIR and SE images were calculated using those suitable combinations and compared.
Our simulation clarified that the CSF-PVE artifacts in the standard synthetic FLAIR increase T as the water volume increases in a voxel, and the volunteer MR brain study demonstrated that the hyperintense artifacts on synthetic images were reduced to <10% of V in those with the standard synMRI while keeping the tissue SNR by selecting optimal masking parameters on additional long TE images of TE = 300 ms. In addition, the wsup-synthetic SE provided better gray-white matter contrasts compared with the wsup-synthetic FLAIR while keeping CSF suppression.
Our proposed Twsup-synMRI technique makes it easy to reduce the CSF-PVE artifacts problematic in the synthetic FLAIR images using the current synMRI technique by adding long TE images and simple processing. Although further optimizations in data acquisition and processing techniques are required before actual clinical use, we expect our technique to become clinically useful.
本研究旨在评估我们提出的新的合成磁共振成像（synMRI）技术与基于 T 的水抑制（Twsup）相结合，以减少脑脊液（CSF）部分容积效应（PVE）。这些 PVE 在传统 synMRI 技术获得的 T 加权液体衰减反转恢复（FLAIR）图像中是一个问题。
我们的 Twsup 是通过在 T 衰减校正后从最初获得的图像中减去另外获得的长 TE 自旋回波（SE）水信号主导图像，并使用水体积（V）图对长 TE 图像进行掩蔽来保留组织 SNR，然后进行定量映射，再计算合成图像来实现的。进行了一项基于包括组织和水中一个体素的两室模型的模拟研究和志愿者磁共振研究，以评估我们提出的方法。通过实验评估和优化长 TE 等参数和掩蔽中的阈值值。生成标准和带 Twsup 的定量参数图，然后使用合适的组合计算并比较带 Twsup 的合成 FLAIR 和 SE 图像。
我们的模拟结果表明，在标准合成 FLAIR 中，随着体素中脑脊液体积的增加，CSF-PVE 伪影的 T 值增加，志愿者磁共振脑研究表明，通过选择最佳的掩蔽参数对额外的长 TE 图像（TE = 300ms）进行处理，在使用标准 synMRI 时，在合成图像上的高信号伪影减少到 <10%的 V，同时保持组织 SNR。此外，与带 Twsup 的合成 FLAIR 相比，带 Twsup 的合成 SE 提供了更好的灰白质对比度，同时保持 CSF 抑制。
我们提出的 Twsup-synMRI 技术通过添加长 TE 图像和简单的处理，很容易减少当前 synMRI 技术中合成 FLAIR 图像中存在的 CSF-PVE 伪影。尽管在实际临床应用之前需要进一步优化数据采集和处理技术，但我们期望我们的技术能够具有临床应用价值。
