Medical Image Registration

Abstract: Image registration of X-ray images is used to correctly align the patient before the cancer tumour is treated with sets of high dose X-ray radiation. Before the first treatment, a simulated X-ray image is taken showing the best possible localisation of the tumour. From then on, after each of the radiation treatments of the tumour, a low dose of the X-ray theurapeutic radiation is used to take an image of the tumour and its surroundings. This so called portal X-ray image is compared to the simulated image to decide whether the patient should be moved before the next treatment in order to improve the accuracy of the theurapeutic beam and, hence, prevent the high dose radiation from hitting other surrounding tissues close to the tumour. Due to differences in quality of the X-ray plates used for the recording of the simulated and the portal image, the images differ a lot in contrasts, noise level, and possibly even scale and size. The diverse quality of the images is the main problem of the image registration task. At present, the comparison of the X-ray images is carried out by hand. A software for automating the process would decrease the influence of human intuition on the treatment, decrease the treatment time, and enable less qualified personnel to carry out the treatment. Much research has already been done within the field of image registration, many with various results. The preceding pilot study suggests that a deeper study, that would go beyond the scope of this project, is needed for the task. This report strives for presenting fields of possible approaches to the problem and tests performed within these fields. Hopefully, the report will give some guidance on directions that a future research could take.