Procedural blood vessel generation for surgical training of twin-to-twin transfusion syndrome

Twin to twin transfusion syndrome (TTTS) is a life threatening fetal condition in which two monochorionic twins share their placental blood supply unevenly. To ensure survival, the blood supply must be severed using surgical fetal laser photocoagulation. This is a rare high stakes procedure, making surgical training critical to improve patient outcomes. In order to combat the limitations of traditional apprentice models, the Ontario Fetal Centre has pioneered a virtual reality training simulator for TTTS surgical training. This work expands on this existing simulator through the addition of procedurally generated blood vessels on the simulated placenta, allowing for the generation of an infinite number of surgical training scenarios. A 2 tiered procedure is introduced for creating procedural blood vessels. First, “core vessels” are created through endpoint sampling, vessel skeleton creation, spline interpolation smoothing, and point projection, modeling vasculogenesis. Next, smaller branches are created to simulate angiogenesis under a similar procedure. Once the full vessel skeleton is created, mesh generation is performed. After the generation system is introduced, a technical and clinical evaluation is provided to support basic efficacy of the generation system. Adequate variation and accurate anatomical quality of the vessels is supported through expert feedback and a technical evaluation of vessel coverage and anatomically incorrect collisions. Additionally, usability of the system for further surgical training is demonstrated through user study feedback, consisting of the Michigan Standard Simulation Experience Scale, NASA TLX, and System Usability Survey. Limitations demonstrated in the study and future improvements are also discussed.