Manual Registration of 2D Abdominal CT Pre Contrast and Post Contrast Images Having Lesions

Abdominal CT images have different intensity levels of the anatomical regions within the abdomen. In addition to this lesions also possess intensity levels that can be distinguished from the anatomy itself. However this distinction is less in pre contrast images and more in post contrast images. Radiologists therefore use post contrast images for diagnosis. To improve diagnostic accuracy pre and post contrast 2D abdominal CT images with lesions are registered by locating feature points which are a hybrid of the centres of lesions, points lying on the boundary of lesion, image centroids and image corners located in pre contrast and post contrast images. Use of Thin Plate Splines as transformation function is made to map the small deformations in the image which may have occurred due to uptake of contrast, patient movement etc. Thin plate splines is able to take care of small elastic deformations that occur over a small region. Considerable improvement in average intensity, contrast and uniformity of the post contrast image is observed when it is registered to the pre contrast image. Increase in number of feature points increases correlation coefficient of the pre and post contrast abdominal 2D CT images provided feature points are accurately chosen.