Image Registration: A Review of Elastic Registration Methods Applied to Medical Imaging

Abstract

Image registration is mapping different images of the same scene which have undergone changes due to time, position or inherent changes in the image. In medical images these may be due to motion artifact, breathing, heartbeat, etc which are difficult to register only by rigid registration and need a local transformation to correct the deformations that are elastic in nature at the local level. This is corrected by applying elastic registration applied to the initially rigid registered images. Such mapping of coordinates of the image that has undergone transformation on account of one or a combination of these factors calls for hybrid registration. A number of elastic registration methods as applied to medical imaging have been discussed in this paper and results for hybrid registration of pre contrast and post contrast abdominal CT images are shown. The resulting images show increase in correlation coefficient and Mutual information after hybrid registration, a decrease in Mean square error with differences being minimised after registration. This helps in improving diagnostic accuracy.