Interactive atlas of congenital
craniofacial malformations
Per Larsen (1), Sven Kreiborg(1), Flemming Vinther(1), Tron Darvann (1), T. Schiemann(2), U. Tiede(2) and K. H. Höhne(2).

1) 3D-Lab*, School of Dentistry, University of Copenhagen. email: postmaster@lab3d.odont.ku.dk http://www.lab3d.odont.ku.dk/
2) Institute of Mathematics and Computer Science in Medicine , Department of Computer Science in Medicine, University of Hamburg.

Abstract.

A true 3D interactive atlas of the craniofacial region in patients with severe congenital craniofacial anomalies, so far, as Apert and Crouzon syndromes, has been developed using an extended version of the VOXEL-MAN software (Höhne el al., 1992).

The atlas is based on CT-data obtained in relation to the clinical treatment of the patients (diagnosis, surgical treatment planning and follow-up). The new atlas is, thus, in several instances based on 2 or 3 CT-volumes of the same patient collected over time. This gives a unique opportunity to understand the pathology, and its change during growth, and it opens for simulation of craniofacial surgery and growth. Furthermore, the atlas will be useful in the training of medical and dental students.

Description.

An early version of an atlas featuring three successive stages from a girl with Apert syndrome has been developed. By segmenting the different anatomical parts (bones)of the skull at each of the three stages, a tool for visualizing change over time, both for clinical, scientific and educational purpoes has been developed. The clinical value is related to improved understanding of the primary malformation, the resultant dysplastic craniofacial growth and the effect of craniofacial surgery on the subsequent development.

The patient was scanned at:


Thus, from stage 1 to stage 2 all changes were due to dysplastic and compensatory growth in relation to premature synostosis of the coronal sutures bilaterally and fusion of maxillary sutures. A cranioplasty was carried out at 21 months of age with advancement of the supraorbital region and the frontal bone. Therefore, the 3D reconstruction of the scanning at 7 years of age document the combined result of surgery and subsequent craniofacial growth from 21 months to 7 years.

The creation of the atlas is being carried out (stage 3 is not yet fully segmented and therefore not shown) using an extended version of the VOXEL-MAN atlas (Höhne el al., 1992). This atlas is a 3-dimensional visualization atlas which provides an intuitive graphical interface for interactively manipulating pre-segmented anatomical structures (both hard and soft-tissues) from 3D volumes such as CT- and MR-data . It is also a knowledge data base with anatomical annotations and can be extented with corresponding histological images.

The VOXEL-MAN segmentation part (Schiemann et al., 1992) provides low level segmentation tools working in 3D, e.g. thresholding, morphological operations, connected component analysis, region filling, and boolean operations.

The segmentation part of the VOXEL-MAN software provided by Professor Höhne's group to the 3D-Lab, has enabled us to use the software to visualize and segment CT-data on individual patients from the Craniofacial Team at the National University Hospital of Denmark in Copenhagen and the School of Dentistry, University of Copenhagen. The method will undoubtedly lead to new important information about these rare and complex anomalies and will thereby, hopefully, lead to improved over-all treatment and care. A spin-off of information related to the general biological mechanisms involved in craniofacial morphogenesis may be expected.

Finally, the development of atlases on rare malformations will be useful in the training of medical and dental students.

             
Fig 1A: The different anatomical structures of the skull at stage 1 is colored to highlight their shape and boundary.
Fig 1B: Stage 2 color coded in the same way as in fig 1A. By comparing the two color coded models, an impression of the growth process is gained.

                
Fig 2A: Anatomical structers may be annotated.
Fig 2B: Same as for fig 2A. Note: The frontal and parietal bone is shown as one structure due to the complete closure of the growth zone between the two parts.

            
Fig 3A: All anatomical structures can be removed one by one in order to visualize the internal surfaces and boundaries.
Fig 3B: It is also possible to visualize any of the anatomical structures transparently.


ACKNOWLEDEMENTS

The authors are grateful to Dr. Aase Wagner and Karen-Lisbeth Dirksen, Department of Radiology, The National University Hospital of Denmark for providing us with the CT-data, and to the clinical co-ordinator of the Craniofacial Team at this hospital, Dr. Flemming Skovby, Department of Pediatrics.

References

K. H. Höhne, M.Bomans, M.Riemer, R.Schubert, U.Tiede, and W.Lierse, "A 3D anatomical atlas based on a volume model," IEEE Comput. Graphics Appl., vol.12, no.4, pp.72-78, 1992.

T. Schiemann, M. Bomans, U. Tiede, and K. H. Höhne, "Interactive 3D-segmentation," in Visualization in Biomedical Computing II, Proc. SPIE 1808 (R. A. Robb, ed.), (Chapel Hill, NC), pp. 376-383, 1992.


*3DLab.
is the
Research and Development Laboratory for 3D Image Processing and Reconstruction
at the
National University Hospital of Denmark,
School of Dentistry, University of Copenhagen,
and Department of Mathematical Modelling, Technical University of Denmark.