Haptic Feedback Forces Applied to Radiation Treatment Planning

For children who are receiving radiation therapy for cancer, it is very important that the organ contours used for the radiation treatment plan be as accurate as possible. In children, the organs are reduced in size, making the task of defining such organ contours more difficult than for an adult. The goal of this project is to increase the accuracy of this contour definition process (the “task”) while not increasing the time required for the task. Reducing the required time required to perform this task would be an added benefit.

The haptic device is capable of producing several different kinds of force: spring loading, viscous, direct, frictional, and hard surface. The 3D visualization software can compute functions over the pixels or voxels, to, for example, define edges using several different filters. At present, the software implements a gradient force. The haptic force produced from this gradient can be used as is or can be modified by an exponential. Additionally, either of these can be combined with a viscous force based on the velocity and direction of the haptic device movement. This existing version has been shown (in an earlier exjobb) to reduce the time required to draw a contour, although the number of volunteers was not sufficiently large to indicate if there was a statistically significant difference in the accuracy, there was a significant reduction in the time required.

The task in this exjobb will be to (1) design an experiment which will use different types of haptic forces, (2) conduct this experiment using a number of volunteers, and (3) analyze the results to determine which gives the best improvement with regard to accuracy and time in comparison with the null hypothesis - i.e., without haptic force.