Shigenaga Yutaka, Takenaka Daisuke, Hashimoto Tomohisa, Ishida Takayuki
Department of Radiology, Hyogo Cancer Center.
Division of Health Sciences, Graduate School of Medicine, Osaka University.
Magn Reson Med Sci. 2021 Mar 1;20(1):76-82. doi: 10.2463/mrms.mp.2019-0161. Epub 2020 Apr 7.
The combination of modified Dixon (mDixon) and periodically rotated overlapping parallel lines with enhanced reconstruction sequence with two interleaved echoes, which promotes uniform fat-suppression and motion insensitivity, has recently become available for commercial magnetic resonance imaging (MRI) scanners. To compare the robustness of this combination sequence with that of standard Cartesian mDixon sequence for fat-suppressed T-weighted imaging in clinical head and neck MRI.
Fifty patients with head and neck tumors were involved this study. All patients underwent MRI using both the combination and standard sequences. Two radiologists independently scored motion artifacts and water-fat separation error using a 4-point scale (1, unacceptable; 4, excellent). Furthermore, comprehensive comparative evaluation was performed using a 5-point scale (1, substantially inferior; 5, substantially superior). Data were statistically analyzed using the Wilcoxon signed-rank test.
In the motion artifact assessment, ratings of 3 or 4 points were assigned to 45% (observer-1, 58.0%; observer-2, 32.0%) and 97% (100%; 94.0%) of images for the standard and combination sequences, respectively (P < 0.001). For the water-fat separation error assessment, ratings of 3 or 4 points were assigned to 100% (100%; 100%) and 85% (84.0%; 86.0%) of images, respectively (P < 0.001). In the comprehensive evaluation, of the 100 cases (observer-1, 50; observer-2, 50), 96 were rated at four or five points. In cases with slight or no motion artifacts and water-fat separation errors, the combination sequence was superior to the standard sequence in term of noise and sharpness, and equal in terms of contrast.
Although water-fat separation errors increased significantly in the combination sequence, most of these were acceptable. The significantly decreased motion artifacts in the combination sequence significantly improved image quality overall.
改良狄克逊（mDixon）与具有两个交错回波的周期性旋转重叠平行线增强重建序列相结合，可促进均匀脂肪抑制和运动不敏感，最近已应用于商用磁共振成像（MRI）扫描仪。比较这种组合序列与标准笛卡尔mDixon序列在临床头颈MRI脂肪抑制T加权成像中的稳健性。
本研究纳入50名头颈部肿瘤患者。所有患者均使用组合序列和标准序列进行MRI检查。两名放射科医生使用4分制（1分，不可接受；4分，优秀）对运动伪影和水脂分离误差进行独立评分。此外，使用5分制（1分，明显较差；5分，明显较好）进行综合比较评估。采用Wilcoxon符号秩检验对数据进行统计学分析。
在运动伪影评估中，标准序列和组合序列分别有45%（观察者1为58.0%；观察者2为32. 0%）和97%（观察者1为100%；观察者2为94.0%）的图像评分为3分或4分（P<0.001）。在水脂分离误差评估中，标准序列和组合序列分别有100%（观察者1为100%；观察者2为100%）和85%（观察者1为84.0%；观察者2为86.0%）的图像评分为3分或4分（P<0.001）。在综合评估中，100例患者（观察者1为50例；观察者2为50例）中有96例评分为4分或5分。在运动伪影和水脂分离误差轻微或无的情况下，组合序列在噪声和清晰度方面优于标准序列，在对比度方面相当。
虽然组合序列中的水脂分离误差显著增加，但大多数是可接受的。组合序列中运动伪影的显著减少总体上显著提高了图像质量。
