Medical Illustration in Conjoined Twin Surgical Separation Planning

In the last posts I highlighted the use of biomedical visualisation in scientific research and education, it also has an important role in medicine. Hospitals employ medical illustrators to help specialists and patients visualise medicine and science in a way that is simple to understand, interactive and interesting.

Medical illustrators are professional artists that create medical illustrations using traditional and digital techniques to represent anatomy with individual images from X–rays and CT scans to prepare the course of surgery. They also work in three dimensions, creating anatomical teaching models, patient simulators, and facial prosthetics. Medical Illustrators function as consultants and administrators within the field of bio communication, their drawings teaching others within the surgical profession and at medical schools. An example of this role includes planning the surgical separation of conjoined twins with 3D medical imaging, scientific visualisation and anatomic illustration.

conjoined

Illustration developed for the separation of the Carlsen twins at the Mayo Clinic USA.

Understanding the anatomy of conjoined twins is difficult, accurate models and illustrations are important for pre-surgical assessments and planning as well as for reference during the actual operative procedure. The separation of conjoined twins is one of the most intricate procedures in medicine today, requiring massive teams of surgeons, nurses, anesthesiologists, and care givers to operate in harmony. Models provide a valuable basis for communication between the groups of specialists who are involved in the cases.

Conjoined twins develop as a result of the failed fusion of a single fertilized ovum however it is theorized that cranial fusion occurs between two separate embryos prior to the end of the 4th week of gestation. Craniopagus twins are conjoined twins who are fused at the cranium, those that survive birth present unique challenges in necessary surgical separation. This condition occurs when in the embryonic development process of Neurulation, the cranial neuropores remain open which are responsible for the ultimate fusion and formation of the brain stem and central nervous system. The fusion occurs from neural folds of two separate, dorsally oriented embryonic discs, and the union can occur only after the ectoderm is disrupted to allow the neural and surface ectodermal layers to separate from each other.

craniopagus

Stereolithography model produced of the bone and vascular structures of 2-year-old vertical craniopagus twins

Total craniopagus twins are defined as sharing extensive surface area with widely connected cranial cavities. There are four main categories- Frontal, Temporoparietal , Occipital and Parietal the latter considered the most unusual as the craniums of the two twins share the most veins, lobes and circulatory, often described as one brain shared by two individuals. In the last-half century advances have proven that a successful outcome is possible following separation of total craniopagus twins.

The neurosurgical aspects of craniopagus twin cases involve massive amounts of data from CT and MRI and angiograms imaging studies. Illustration assists surgeons in visualizing medical data produced. Neurosurgical applications for anatomical modelling centre on visualising vascular anomalies, bony anatomy representations for craniosynostosis surgery, and cranioplasty preparation. The recent use of modelling for the visualisation of the vascular systems of craniopagus twins has been a great benefit to neurosurgeons involved in these cases.

One team of surgeons used high-end virtual reality equipment to study the anatomy and rehearse the separation of a pair of vertical craniopagus twins. The team also used RP-generated anatomical models (3D printing) of the twins’ skulls and brain vasculature for identification of critical areas. Without advanced medical imaging and RP generated anatomical models, the planning for these operations would have been radically more difficult at best and impossible at worst.

conjoined dummies

Whole body anatomical model produced using 3D printing and in use by the hospital operating room staff, preparing to separate 2-year-old vertical craniopagus twins.

References

Christensen, A. Humpheries, S. Keith, G. and Swift,D. (2004) “Advanced “tactile” medical imaging for separation surgeries of conjoined twins” PubMed, Vol 20 pp 547-553

Goodrich, J. and Staffenberg, D.(2004) “Craniopagus Twins: Clinical and Surgical Management.” Child’s Nervous System, Vol 20.8-9: pp 618-24.

Kato K, Ishiguchi T, Maruyama K, Naganawa S, Ishigaki T (2001) Accuracy of plastic replica aortic aneurysm using 3D-CT data for transluminal stent-grafting: experimental and clini- cal evaluation.J Comput Assist

Muller A, Krishnan K,G. Uhl E, Mast,G. (2003) The application of rapid proto- typing techniques in cranial recon- struction and preoperative planning in neurosurgery. J Craniofac Surg Vol 14 pp 899–914

Perez-Arjona E, Dujovny M, Park H (2003) Stereolithography: neurosurgical and medical implications. Neurol Res Vol 25 pp 227

Perlyn CA, Marsh JL, Vannier MW, Kane AA, Koppel P, Clark KW, Christensen GE, Knapp R, Lo LJ, Govier D (2001) The craniofacial anomalies archive at St Louis Children’s Hospital: 20 years of craniofacial imaging experience. Plast Reconstr Surg Vol 108 pp 1862–1870

Wurm G, Tomancok B, Pogady P, Holl K, Trenkler J (2004) Cerebrovascular stereolithographic biomodeling for an- eurysm surgery. Technical note.

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