Department of Radiology, Balgrist University Hospital, Forchstrasse 340, Zurich 8008, Switzerland; Faculty of Medicine, University of Zurich, Zurich, Switzerland.
Department of Orthopaedics and Rehabilitation, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, USA.
Foot Ankle Clin. 2023 Sep;28(3):529-550. doi: 10.1016/j.fcl.2023.05.008. Epub 2023 Jun 20.
MRI is a valuable tool for diagnosing a broad spectrum of acute and chronic ankle disorders, including ligament tears, tendinopathy, and osteochondral lesions. Traditional two-dimensional (2D) MRI provides a high image signal and contrast of anatomic structures for accurately characterizing articular cartilage, bone marrow, synovium, ligaments, tendons, and nerves. However, 2D MRI limitations are thick slices and fixed slice orientations. In clinical practice, 2D MRI is limited to 2 to 3 mm slice thickness, which can cause blurred contours of oblique structures due to volume averaging effects within the image slice. In addition, image plane orientations are fixated and cannot be changed after the scan, resulting in 2D MRI lacking multiplanar and multiaxial reformation abilities for individualized image plane orientations along oblique and curved anatomic structures, such as ankle ligaments and tendons. In contrast, three-dimensional (3D) MRI is a newer, clinically available MRI technique capable of acquiring high-resolution ankle MRI data sets with isotropic voxel size. The inherently high spatial resolution of 3D MRI permits up to five times thinner (0.5 mm) image slices. In addition, 3D MRI can be acquired image voxel with the same edge length in all three space dimensions (isotropism), permitting unrestricted multiplanar and multiaxial image reformation and postprocessing after the MRI scan. Clinical 3D MRI of the ankle with 0.5 to 0.7 mm isotropic voxel size resolves the smallest anatomic ankle structures and abnormalities of ligament and tendon fibers, osteochondral lesions, and nerves. After acquiring the images, operators can align image planes individually along any anatomic structure of interest, such as ligaments and tendons segments. In addition, curved multiplanar image reformations can unfold the entire course of multiaxially curved structures, such as perimalleolar tendons, into one image plane. We recommend adding 3D MRI pulse sequences to traditional 2D MRI protocols to visualize small and curved ankle structures to better advantage. This article provides an overview of the clinical application of 3D MRI of the ankle, compares diagnostic performances of 2D and 3D MRI for diagnosing ankle abnormalities, and illustrates clinical 3D ankle MRI applications.
磁共振成像（MRI）是诊断广泛的急性和慢性踝关节疾病的有价值的工具，包括韧带撕裂、肌腱病和骨软骨病变。传统的二维（2D）MRI 提供了高图像信号和解剖结构的对比度，可准确描述关节软骨、骨髓、滑膜、韧带、肌腱和神经。然而，2D MRI 存在局限性，例如厚切片和固定切片方向。在临床实践中，2D MRI 的切片厚度限制在 2 到 3 毫米，这会由于图像切片内的体积平均效应而导致斜结构的轮廓模糊。此外，图像平面方向是固定的，在扫描后无法更改，导致 2D MRI 缺乏针对斜向和弯曲解剖结构（如踝关节韧带和肌腱）的个体化图像平面方向的多平面和多轴向重建能力。相比之下，三维（3D）MRI 是一种较新的、临床可用的 MRI 技术，能够获取具有各向同性体素大小的高分辨率踝关节 MRI 数据集。3D MRI 固有的高空间分辨率允许使用多达五倍薄（0.5 毫米）的图像切片。此外，3D MRI 可以在所有三个空间维度（各向同性）中以相同的边缘长度获取图像体素，允许在 MRI 扫描后进行不受限制的多平面和多轴向图像重建和后处理。临床 3D MRI 以 0.5 到 0.7 毫米的各向同性体素大小可分辨最小的解剖踝关节结构和韧带、肌腱纤维的异常、骨软骨病变和神经。在获取图像后，操作人员可以沿着任何感兴趣的解剖结构单独对齐图像平面，例如韧带和肌腱段。此外，弯曲的多平面图像重建可以将多轴向弯曲结构（如外踝周围肌腱）的整个行程展开到一个图像平面中。我们建议在传统的 2D MRI 方案中添加 3D MRI 脉冲序列，以更好地可视化小的和弯曲的踝关节结构。本文概述了踝关节 3D MRI 的临床应用，比较了 2D 和 3D MRI 诊断踝关节异常的诊断性能，并说明了临床 3D 踝关节 MRI 的应用。
