Locally affine diffeomorphic surface registration for planning of metopic craniosynostosis surgery

Abstract

The outcome of cranial vault reconstruction for the surgical treatment of craniosynostosis heavily depends on the surgeon's expertise because of the lack of an objective target shape. We introduce a surface-based diffeomorphic registration framework to create the optimal post-surgical cranial shape during craniosynostosis treatment. Our framework estimates and labels where each bone piece needs to be cut using a reference template. Then, it calculates how much each bone piece needs to be translated and in which direction, using the closest normal shape from a multi-atlas as a reference. With our locally affine approach, the method also allows for bone bending, modeling independently the transformation of each bone piece while ensuring the consistency of the global transformation. We evaluated the optimal plan for 15 patients with metopic craniosynostosis. Our results showed that the automated surgical planning creates cranial shapes with a reduction in cranial malformations of 51.43% and curvature discrepancies of 35.09%, which are the two indices proposed in the literature to quantify cranial deformities objectively. In addition, the cranial shapes created were within healthy ranges.

Fig. 1

(a) Anterior view of the cranium of one patient with the left (LF) and right (RF) frontal bones segmented. (b) Bone piece cuts labeled using the proposed bone cut template. Label 1 indicates the supra-orbital bar, labels 2-3 are subdivisions of the LF bone, and labels 4-5 are subdivisions of the RF bone. The rest of the cranium is shown in black.

Fig. 2

(a) Superior (left) and anterior (right) views of the malformations in the frontal bones for the same case shown in Fig. 1, both for its pre-operative cranial mesh representation (top) and its simulated post-operative cranial shape obtained with the optimal surgical plan (bottom). (b) Curvature discrepancies in the frontal bones for the same case. The rest of the cranium is shown in white. The black wireframe represents the closest normal shape from the multi-atlas.