Hansis Eberhard, Lorenz Cristian
Philips Research, Röntgenstraße 24-26, 22335, Hamburg, Germany.
Int J Comput Assist Radiol Surg. 2016 Jul;11(7):1285-95. doi: 10.1007/s11548-015-1328-5. Epub 2015 Dec 11.
PURPOSE: Many medical imaging tasks require the detection and localization of anatomical landmarks, for example for the initialization of model-based segmentation or to detect anatomical regions present in an image. A large number of landmark and object localization methods have been described in the literature. The detection of single landmarks may be insufficient to achieve robust localization across a variety of imaging settings and subjects. Furthermore, methods like the generalized Hough transform yield the most likely location of an object, but not an indication whether or not the landmark was actually present in the image. METHODS: For these reasons, we developed a simple and computationally efficient method combining localization results from multiple landmarks to achieve robust localization and to compute a localization confidence measure. For each anatomical region, we train a constellation model indicating the mean relative locations and location variability of a set of landmarks. This model is registered to the landmarks detected in a test image via point-based registration, using closed-form solutions. Three different outlier suppression schemes are compared, two using iterative re-weighting based on the residual landmark registration errors and the third being a variant of RANSAC. The mean weighted residual registration error serves as a confidence measure to distinguish true from false localization results. The method is optimized and evaluated on synthetic data, evaluating both the localization accuracy and the ability to classify good from bad registration results based on the residual registration error. RESULTS: Two application examples are presented: the identification of the imaged anatomical region in trauma CT scans and the initialization of model-based segmentation for C-arm CT scans with different target regions. The identification of the target region with the presented method was in 96 % of the cases correct. CONCLUSION: The presented method is a simple solution for combining multiple landmark localization results. With appropriate parameters, outlier suppression clearly improves the localization performance over model registration without outlier suppression. The optimum choice of method and parameters depends on the expected level of noise and outliers in the application at hand, as well as on the focus on localization, classification, or both. The method allows detecting and localizing anatomical fields of view in medical images and is well suited to support a wide range of applications comprising image content identification, anatomical navigation and visualization, or initializing the pose of organ shape models.
目的:许多医学成像任务需要检测和定位解剖标志点,例如用于基于模型的分割的初始化或检测图像中存在的解剖区域。文献中已经描述了大量的标志点和目标定位方法。单个标志点的检测可能不足以在各种成像设置和受试者中实现稳健的定位。此外,像广义霍夫变换这样的方法可以得出物体最可能的位置,但无法表明该标志点是否真的存在于图像中。 方法:出于这些原因,我们开发了一种简单且计算高效的方法,该方法结合多个标志点的定位结果以实现稳健的定位并计算定位置信度度量。对于每个解剖区域,我们训练一个星座模型,该模型指示一组标志点的平均相对位置和位置可变性。使用闭式解,通过基于点的配准将该模型配准到在测试图像中检测到的标志点。比较了三种不同的离群值抑制方案,其中两种基于残余标志点配准误差使用迭代重新加权,第三种是随机抽样一致性算法(RANSAC)的变体。平均加权残余配准误差用作区分真实和错误定位结果的置信度度量。该方法在合成数据上进行了优化和评估,评估了定位准确性以及基于残余配准误差将良好与不良配准结果分类的能力。 结果:给出了两个应用示例:创伤CT扫描中成像解剖区域的识别以及不同目标区域的C形臂CT扫描基于模型的分割的初始化。使用所提出的方法对目标区域的识别在96%的情况下是正确的。 结论:所提出的方法是一种用于组合多个标志点定位结果的简单解决方案。通过适当的参数,离群值抑制明显优于无离群值抑制的模型配准,从而提高了定位性能。方法和参数的最佳选择取决于手头应用中预期的噪声和离群值水平,以及对定位、分类或两者的关注重点。该方法允许在医学图像中检测和定位解剖视野,非常适合支持包括图像内容识别、解剖导航和可视化或初始化器官形状模型的姿态等广泛的应用。
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Med Image Anal. 2013-1-27
Int J Comput Assist Radiol Surg. 2013-2-9
IEEE Trans Med Imaging. 2012-8-31
IEEE Trans Med Imaging. 2010-9-27
IEEE Trans Med Imaging. 2008-9