InitRech 2015/2016, sujet 11

Summary

When a patient suffers cardiac arrhythmias or heart failure, caused by an abnormal electrical activity in the myocardium, the standard procedure is to locate where the problem come from, and then destroy the cells that creates the unusual heart-beating by heating them using radio frequency ablation.

In order to train rookie surgeons on this kind of surgery, HAL proposed an interactive training system that allows the surgeons to practice based on a software called SOFA. Even if system like that already exist, the one introduce in this article (based on a device that already exist) combines a biophysical modeling of cardiac electrophysiology with an endovascular catheterization. The simulating framework allows to model a mapping of the heart, to do the ablation with real-time feedback, and then gives a synthesis of the surgery.

Based on an European database, a 3D view of the endovascular navigation around the heart is first built, using image visualization framework and software. Then, a venial view is also made, using a data set from a company. To finish, they simulate the heart beating by using an algorithm, which provides in the end the cardiac motion.

The GPU used in the program is based on Mitchell Schaeffer model. They choose this model because all 5 parameters had a physiological meaning, and the simulation is more acurate with this method. It captures the potential V_M of the transmembrane. In order to improve the result of the computer, they choose to apply this simulation only on the ventricules. They explain that it can be done because ventricles and atria are electrically isolated. With more than 30k elements, the electrophysiology of the ventricle is computed on a mesh. The time step used on this part is 10^-4 s. To do every simulations at the same time, they use threads on the CPU with a scheduling structure : one thread for endovascular navigation and electrophysiology simulations, and another thread for the graphic view of the simulation. Both thread are asynchronous, because the time step for navigation simulation is greater than the time step mentioned before (0.02s & 10^-4 s).