Young A A
Department of Anatomy with Radiology, University of Auckland, New Zealand.
Med Image Anal. 1999 Dec;3(4):361-72. doi: 10.1016/s1361-8415(99)80029-2.
Although magnetic resonance tissue tagging is a useful tool for the non-invasive measurement of three-dimensional (3-D) heart wall motion, the clinical utility of current analysis techniques is limited by the prohibitively long time required for image analysis. A method was therefore developed for the reconstruction of 3-D heart wall motion directly from tagged magnetic resonance images, without prior identification of ventricular boundaries or tag stripe locations. The method utilized a finite-element model to describe the shape and motion of the heart. Initially, the model geometry was determined at the time of tag creation by fitting a small number of guide points which were placed interactively on the images. Model tags were then created within the model as material surfaces which defined the location of the magnetic tags. An objective function was derived to measure the degree of match between the model tags and the image stripes. The objective was minimized by allowing the model to deform directly under the influence of the images, utilizing an efficient method for calculating image-derived motion constraints. The model deformation could also be manipulated interactively by guide points. Experiments were performed using clinical images of a normal volunteer, as well as simulated images in which the true motion was specified. The root-mean-squared errors between the known and calculated displacement and strain for the simulated images were similar to those obtained using previous stripe-tracking and model-fitting methods. A significant improvement in analysis time was obtained for the normal volunteer and further improvements may allow the method to be applied in a 'real-time' clinical environment.
尽管磁共振组织标记是一种用于非侵入性测量三维（3-D）心脏壁运动的有用工具，但当前分析技术的临床实用性受到图像分析所需时间过长的限制。因此，开发了一种直接从标记的磁共振图像重建三维心脏壁运动的方法，无需事先识别心室边界或标记条带位置。该方法利用有限元模型来描述心脏的形状和运动。最初，通过在图像上交互式放置少量引导点来确定标记创建时的模型几何形状。然后在模型中创建模型标记作为定义磁性标记位置的材料表面。导出一个目标函数来测量模型标记与图像条纹之间的匹配程度。通过允许模型在图像的影响下直接变形，利用一种计算图像衍生运动约束的有效方法，使目标最小化。模型变形也可以通过引导点进行交互式操作。使用正常志愿者的临床图像以及指定了真实运动的模拟图像进行了实验。模拟图像的已知位移和应变与计算位移和应变之间的均方根误差与使用先前条纹跟踪和模型拟合方法获得的误差相似。正常志愿者的分析时间有了显著改善，进一步的改进可能使该方法能够应用于“实时”临床环境。
