Haptic virtual fixture for robotic cardiac catheter navigation.

In manual or robot-assisted catheter intervention, excessive manipulation force may cause tissue perforation. Using images acquired by an imaging device routinely used for catheter interventions such as X-ray fluoroscopy, the structure and size of blood vessels and the relative position of the catheter tip inside the vessel can be obtained. To prevent collision of the catheter tip and the vessel wall, vision-assisted control methods using forbidden-region virtual fixture (FRVF) technique can be utilized and an experimental implementation has been performed in this study. A master-slave configured robotic platform for cardiac catheter was used for this study. The robotic master handle can provide haptic rendering to the user. A vessel phantom model mimicking human vasculature for the inner radii was fabricated for simulated intervention experiments. A digital optical camera was used for image acquisition. After the vessel phantom and the catheter tip were segmented, distance between the vessel centerline and the catheter tip was calculated and the forbidden region that the catheter tip should keep away from was set for the safe catheter manipulation. Virtual force generation algorithm was implemented for feeding the signal indicating the catheter tip penetrating into the forbidden region back to the user in the robotic master handle. To validate the suggested method, in vitro experiments were conducted. Through a chain of image filtering procedures including edge detection, the catheter tip and the vessel wall were able to be well segmented. The virtual force generator worked appropriately. The developed FRVF technique could provide helpful auxiliary information to clinicians for safer manipulation of catheters in cardiac catheterization procedures.