Breast cancer is currently the most prevalent type of cancer. The concluding diagnosis can be obtained with an MRI-guided biopsy. However, due to respiratory movement and human error, the procedure can require multiple attempts, resulting in harmful consequences. To reach the target at the first attempt, the precision of the procedure should be increased, and a robotic system can aid in this. An MRI-compatible concept is designed, but two of its working principles need to be researched before further development.
A possible solution for increasing precision is rotating the needle along the insertion axis. Literature has studied the effect rotation has on insertion force, tissue indentation and target displacement in axial direction, which all show a decrease. However, the effect of rotation on the needle end-point position in lateral direction is not yet researched, and this is a good indication of targeting precision. Therefore, this work has studied the effect of rotation on the precision of the needle end-point position in lateral direction.
The concept uses pneumatically actuated stepper motors for the needle insertion. As the air will be supplied from outside the MRI room, the maximum frequency of air supply is estimated at 10 Hz. Therefore, the effect of an actuation frequency of 10 Hz on the precision of the needle end-point position in lateral direction is studied as well.
Both effects are researched by inserting a needle in a gelatin phantom at different angular velocities and at continuous versus discrete actuation. It is found that rotation significantly decreases the standard deviation in 6 of the 12 cases. The actuation frequency of 10 Hz does not significantly increase the standard deviation in 7 of the 8 cases. These results can be used to further increase the precision of a biopsy robot, whether it is for breast biopsy or another application.