Postoperative evaluation of surgery for craniosynostosis based on image registration techniques

Craniosynostosis consists of a premature fusion of the sutures in an infant skull, which restricts the skull and brain growth. During the last decades there has been a rapid increase of fundamentally diverse surgical treatment methods. At present, the surgical outcome has been assessed using global variables such as cephalic index, head circumerence and intracranial volume. However, the variables have failed in describing the local deformations and morphological changes, which are proposed to more likely induce neurological disorders. In this work an image-registration based method is presented for evaluation of outcomes of craniosynostosis surgical treatments, local quantification of head growth, and indirect intracranial volume change measurements. The developed semiautomatic analysis method is applied to the CT-data of a patient who underwent surgical corrections of sagittal craniosynostosis. As a result the quantification of the local changes between 36 days pre and 9 days postoperative (case a) images were illustrated based on a minimum distance map of two skin isosufaces. Equal comparison was made for 9 days and one year postoperative images (case b). The indirect intracranial volume change was determined to be 370.5 cm² 9 days postoperative and 517.7 cm² one year after the surgery. The volume change of the skull is an estimate of intracranial volume increase and could be usable to compare different surgical techniques. Minimal distance map between preoperative and postoperative CT-images provides both visually informative as well as quantitative information about the local changes in cranial morphology and might also have implications in assessing invasiveness of different techniques. We also verified a high accuracy of registration in terms of mean minimum distance of 0.58 mm and 2.0 mm in cases a and b respectively.