Durastanti Gilda, Leardini Alberto, Siegler Sorin, Durante Stefano, Bazzocchi Alberto, Belvedere Claudio
Movement Analysis Laboratory, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy.
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
Quant Imaging Med Surg. 2019 Aug;9(8):1368-1382. doi: 10.21037/qims.2019.08.08.
Accurate geometrical models of bones and cartilage are necessary in biomechanical modelling of human joints, and in planning and designing of joint replacements. Image-based subject-specific model development requires image segmentation, spatial filtering and 3-dimensional rendering. This is usually based on computed tomography (CT) for bone models, on magnetic resonance imaging (MRI) for cartilage models. This process has been reported extensively in the past, but no studies have ever compared the accuracy and quality of these models when obtained also by merging different imaging modalities. The scope of the present work is to provide this comparative analysis in order to identify optimal imaging modality and registration techniques for producing 3-dimensional bone and cartilage models of the ankle joint.
One cadaveric leg was instrumented with multimodal markers and scanned using five different imaging modalities: a standard, a dual-energy and a cone-beam CT (CBCT) device, and a 1.5 and 3.0 Tesla MRI devices. Bone, cartilage, and combined bone and cartilage models were produced from each of these imaging modalities, and registered in space according to matching model surfaces or to corresponding marker centres. To assess the quality in overall model reconstruction, distance map analyses were performed and the difference between model surfaces obtained from the different imaging modalities and registration techniques was measured.
The registration between models worked better with model surface matching than corresponding marker positions, particularly with MRI. The best bone models were obtained with the CBCT. Models with cartilage were defined better with the 3.0 Tesla than the 1.5 Tesla. For the combined bone and cartilage models, the colour maps and the numerical results from distance map analysis (DMA) showed that the smallest distances and the largest homogeneity were obtained from the CBCT and the 3.0 T MRI via model surface registration.
These observations are important in producing accurate bone and cartilage models from medical imaging and relevant for applications such as designing of custom-made ankle replacements or, more in general, of implants for total as well as focal joint replacements.
在人体关节的生物力学建模以及关节置换的规划和设计中，精确的骨骼和软骨几何模型是必不可少的。基于图像的特定个体模型开发需要图像分割、空间滤波和三维渲染。这通常基于用于骨骼模型的计算机断层扫描（CT）以及用于软骨模型的磁共振成像（MRI）。过去已经广泛报道了这个过程，但从未有研究比较过通过合并不同成像模态获得的这些模型的准确性和质量。本研究的范围是提供这种比较分析，以确定用于生成踝关节三维骨骼和软骨模型的最佳成像模态和配准技术。
对一条尸体腿安装多模态标记，并使用五种不同的成像模态进行扫描：一台标准CT、一台双能CT和一台锥形束CT（CBCT）设备，以及一台1.5特斯拉和一台3.0特斯拉的MRI设备。从这些成像模态中的每一种生成骨骼、软骨以及骨骼与软骨的组合模型，并根据匹配的模型表面或相应的标记中心在空间中进行配准。为了评估整体模型重建的质量，进行了距离图分析，并测量了从不同成像模态和配准技术获得的模型表面之间的差异。
模型之间的配准在模型表面匹配时比相应的标记位置效果更好，尤其是对于MRI。使用CBCT获得了最佳的骨骼模型。使用3.0特斯拉MRI比1.5特斯拉能更好地定义带有软骨的模型。对于骨骼与软骨的组合模型，颜色图和距离图分析（DMA）的数值结果表明，通过模型表面配准，CBCT和3.0T MRI获得的距离最小且均匀性最大。
这些观察结果对于从医学成像中生成精确的骨骼和软骨模型很重要，并且对于诸如定制踝关节置换的设计，或者更一般地说，对于全关节置换以及局部关节置换的植入物设计等应用具有相关性。
