Abstract: Image registration is often used to transform images from different subjects into the same spatial space to ensure more accurate comparisons. With the traditional image registration methods, one image is usually specified as the reference image, while the other images are transformed into the space of the reference image. However, the image randomly selected as the reference image may have significant deviations from the group mean in datasets with large individual differences, causing registration biases and affecting the final results of groupwise comparisons. In this paper, a groupwise registration method based on the topology center of the image set was proposed. With the same open datasets, the performance of the proposed method was compared to that of two widely used traditional methods. The experimental results demonstrated that the proposed method had smaller groupwise registration bias and better registration results. The paper also proposed a simple measure for evaluating groupwise registration bias.

Key words: medical image, topology center, symmetric registration, groupwise registration