Department of Diagnostic Imaging, UCSF Benioff Children's Hospital, 747 52nd Street, Oakland, CA, 94609, USA.
Department of Pediatric Hematology and Oncology, UCSF Benioff Children's Hospital, Oakland, CA, USA.
Pediatr Radiol. 2019 May;49(6):791-800. doi: 10.1007/s00247-019-04349-w. Epub 2019 Feb 6.
Two-point modified Dixon (mDixon) turbo spin-echo (TSE) sequence provides an efficient, robust method of fat suppression. In one mDixon acquisition, four image types can be generated: water-only, fat-only, in-phase and opposed-phase images.
To determine whether PD mDixon TSE water-only and, by proxy, PD in-phase images generated by one acquisition can replace two conventional PD TSE sequences with and without fat suppression in routine clinical MR examination of the knee.
This is a retrospective study of 50 consecutive pediatric knee MR examinations. PD mDixon TSE water-only and PD fat-saturated TSE sequences (acquired in the sagittal plane with identical spatial resolution) were reviewed independently by two pediatric radiologists for homogeneity of fat suppression and detection of intra-articular pathology. Thirteen of the 50 patients underwent arthroscopy, and we used the arthroscopic results as a reference standard for the proton-density fat-saturated and proton-density mDixon results. We used the Kruskal-Wallis rank test to assess difference in fat suppression between the proton-density mDixon and proton-density fat-saturated techniques. We used kappa statistics to compare the agreement of detection of intra-articular pathology between readers and techniques. We also calculated sensitivity, specificity and accuracy between arthroscopy and MR interpretations.
Proton-density mDixon water-only imaging showed significant improvement with the fat suppression compared with proton-density fat-saturated sequence (P=0.02). Each observer demonstrated near-perfect agreement between both techniques for detecting meniscal and ligamentous pathology and fair to substantial agreement for bone contusions, and chondral and osteochondral lesions.
Two-point mDixon water-only imaging can replace conventional proton-density fat-saturated sequence. When same-plane proton-density fat-saturated and non-fat-saturated sequences are required, proton-density water-only and proton-density in-phase image types acquired in the same acquisition shorten the overall examination time while maintaining excellent intra-articular lesion conspicuity.
两点修正 Dixon（m Dixon）涡轮自旋回波（TSE）序列提供了一种高效、稳健的脂肪抑制方法。在一次 m Dixon 采集过程中，可以生成四种图像类型：仅水、仅脂肪、同相位和反相位图像。
确定单次采集生成的 PD m Dixon TSE 仅水和 PD 同相位图像是否可以替代常规膝关节 MR 检查中的两种传统 PD TSE 序列（有和无脂肪抑制）。
这是一项回顾性研究，共纳入 50 例连续的儿科膝关节 MR 检查。两名儿科放射科医生独立评估 PD m Dixon TSE 仅水和 PD 脂肪饱和 TSE 序列（在矢状面以相同的空间分辨率采集），以评估脂肪抑制的均匀性和关节内病变的检出。50 例患者中有 13 例行关节镜检查，我们将关节镜结果作为质子密度脂肪饱和和质子密度 m Dixon 结果的参考标准。我们使用 Kruskal-Wallis 秩检验评估质子密度 m Dixon 和质子密度脂肪饱和技术之间脂肪抑制的差异。我们使用 Kappa 统计比较读者和技术之间关节内病变检出的一致性。我们还计算了关节镜和 MR 解释之间的敏感性、特异性和准确性。
与质子密度脂肪饱和序列相比，质子密度 m Dixon 仅水成像在脂肪抑制方面有显著改善（P=0.02）。每位观察者在两种技术检测半月板和韧带病变方面均表现出近乎完美的一致性，在检测骨挫伤、软骨和骨软骨病变方面表现出良好到中等的一致性。
两点 m Dixon 仅水成像可以替代传统的质子密度脂肪饱和序列。当需要同平面质子密度脂肪饱和和非脂肪饱和序列时，同一次采集获得的质子密度仅水和质子密度同相位图像类型可以缩短整体检查时间，同时保持良好的关节内病变显示。
