Comparing densely calculated facial soft tissue depths for craniofacial reconstruction: Euclidean vs. perpendicular distances

ABSTRACT

For surgical craniofacial reconstruction, preoperative planning may be limited by missing 3D skeletal geometry. In forensic sciences, ‘reconstruction’ models the 3D facial structure from skull geometries using soft-tissue depth mapping. This work investigates ‘reverse engineering’ the forensics’ TD Morpheus model to infer the bony shape from 3D facial surfaces by subtracting tissue depths inwards along the normal vectors. This approach using Euclidean tissue depths successfully estimated the upper and outermost skeletal regions (i.e. frontal, zygoma, and nasal bones) in 24 head CT scans, but concave skeletal surfaces were inaccurately evaluated where the face is convex yielding misshapen anatomy around the orbits and zygomatic arches. A perpendicular tissue depth algorithm was developed to probe inwards along the face’s normal vectors until contacting bone, demonstrating superior performance to the Euclidean depth approach. Accurate regional tissue depths achievable with this approach may provide a useful bridge to connect the 3D face and underlying skull geometry, with the potential for application in craniofacial reconstruction.

KEYWORDS:

• Craniofacial reconstruction
• skull geometry
• soft tissue depth
• Euclidean distance
• perpendicular tissue depth

Acknowledgements

Support for this work has been provided by the Natural Sciences and Engineering Research Council of Canada and FedDev-Ontario.

Abbreviations

three dimensional (3D), two dimensional (2D), computed tomography (CT), tissue depth (TD)

Disclosure statement

No potential conflict of interest was reported by the author(s)

Additional information

Funding

The work was supported by the Natural Sciences and Engineering Research Council of Canada [CGS-D]; FedDev Ontario.

Notes on contributors

Z. Fishman

Zachary Fishman, PhD, is a Post-Doctoral Fellow in the Orthopaedic Biomechanics Lab at the Sunnybrook Research Institute working under the supervision of Dr. Cari Whyne and Dr. Jeffrey Fialkov. Zachary has an undergraduate and Masters degree in Mechanical Engineering, with a focus on material analysis, 3D design and prototyping. Zachary’s research is investigating new translational tools including 3D scanning, 3D printing, and 2D‐3D image analysis. His research focus is to improve the accuracy and workflow in craniofacial reconstruction.

J.A. Fialkov

Jeffrey Fialkov MD, MSc, FRCSC, is Head of the Division of Plastic and Reconstructive Surgery at Sunnybrook Health Sciences Centre and an associate professor in the Department of Surgery with cross-appointment to the Institute of Biomedical Engineering at The University of Toronto. As a fellowship trained craniomaxillofacial surgeon, his clinical focus encompasses the reconstruction of post-traumatic, congenital and post-ablative facial deformities. As part of the University of Toronto teaching faculty, he provides post-graduate supervision in adult craniofacial surgery to fellowship trainees from Canada, the United States, Europe and the Middle East. Dr. Fialkov is also an associate scientist in the Holland Bone and Joint Research Program at Sunnybrook Health Sciences Centre. His research focus is on craniomaxillofacial reconstructive techniques and translational technologies, with an emphasis on biomechanics using cadaveric and in silico modelling. His interest in craniofacial trauma, facial reconstruction and craniomaxillofacial biomechanics has led to the publication of numerous peer-reviewed articles and book-chapters on the subject. In addition, his research interests have led to several innovations in the field including novel surgical techniques and technological innovations such as a novel patented osteo-synthetic system.

C.M. Whyne

Cari Whyne, PhD, FIOR, is the Susanne and William Holland Chair in Musculoskeletal Research at Sunnybrook Health Sciences Centre in Toronto. She is a Senior Scientist and the Director of the Holland Bone and Joint Research Program at Sunnybrook Research Institute and a Full Professor in the Department of Surgery, Institute of Biomedical Engineering and Institute of Medical Sciences at the University of Toronto. Dr. Whyne received her BSc. in Mechanical Engineering from Queen’s University and her PhD from the University of California Berkeley/University of California San Francisco in Bioengineering. The focus of her work is clinically translational bioengineering research. Dr. Whyne’s research integrates biomechanical analyses with basic science, preclinical and clinical investigations, including extensive work in computational image analysis, micro-imaging, machine learning and finite element modelling techniques. Her work also incorporates design, simulation, evaluation and clinical translation of novel less/minimally invasive surgical techniques and devices. The primary foci of Dr Whyne’s research are cancer in bone, biomechanics (spinal, craniomaxillofacial, upper and lower extremity) and fracture fixation/healing.