Hipwell John H, Tanner Christine, Crum William R, Schnabel Julia A, Hawkes David J
University College London, Centre for Medical Image Computing, London, WC1E 6BT U.K.
IEEE Trans Med Imaging. 2007 Sep;26(9):1190-200. doi: 10.1109/TMI.2007.903569.
Establishing spatial correspondence between features visible in X-ray mammograms obtained at different times has great potential to aid assessment and quantitation of change in the breast indicative of malignancy. The literature contains numerous nonrigid registration algorithms developed for this purpose, but existing approaches are flawed by the assumption of inappropriate 2-D transformation models and quantitative estimation of registration accuracy is limited. In this paper, we describe a novel validation method which simulates plausible mammographic compressions of the breast using a magnetic resonance imaging (MRI) derived finite element model. By projecting the resulting known 3-D displacements into 2-D and generating pseudo-mammograms from these same compressed magnetic resonance (MR) volumes, we can generate convincing images with known 2-D displacements with which to validate a registration algorithm. We illustrate this approach by computing the accuracy for two conventional nonrigid 2-D registration algorithms applied to mammographic test images generated from three patient MR datasets. We show that the accuracy of these algorithms is close to the best achievable using a 2-D one-to-one correspondence model but that new algorithms incorporating more representative transformation models are required to achieve sufficiently accurate registrations for this application.
在不同时间获取的乳腺X线片中可见特征之间建立空间对应关系，对于辅助评估和量化乳房中表明恶性肿瘤的变化具有巨大潜力。文献中包含许多为此目的开发的非刚性配准算法，但现有方法存在缺陷，即采用了不适当的二维变换模型假设，并且配准精度的定量估计有限。在本文中，我们描述了一种新颖的验证方法，该方法使用磁共振成像（MRI）衍生的有限元模型模拟乳房合理的乳腺压迫。通过将所得已知的三维位移投影到二维，并从这些相同的压缩磁共振（MR）体积生成伪乳腺X线片，我们可以生成具有已知二维位移的令人信服的图像，用以验证配准算法。我们通过计算应用于从三个患者MR数据集中生成的乳腺X线测试图像的两种传统非刚性二维配准算法的精度来说明这种方法。我们表明，这些算法的精度接近使用二维一一对应模型可达到的最佳精度，但需要结合更具代表性变换模型的新算法才能实现此应用所需的足够精确的配准。
