Prediction of needle deflection based on reaction force analysis for needle puncture robot with CT equipment

Abstract: There is a surgical method called Interventional Radiology (IR). This surgical method is conducted with imaging modality such as CT and X-rays. As compared with conventional survey, IR can be conducted in local anesthesia and this surgical method is minimally-invasive to patients. Recently IR is conducted by surgeons using a forceps and a needle. The minimum size of malignancy is approximately 3mm in diameter. Therefore operator must puncture a needle into body of patients accurately. Because operators conduct procedure close to the CT gantry, operators are exposure to radiation during CT scanning. In order to prevent radiation exposure, operators wear radiation protection aprons and handle a needle using a forceps. However, it is impossible to prevent radiation exposure completely. Zerobot which we have been developing aims to conduct whole process from positioning robot to inserting a needle by remote controlled operation. In this research, Zerobot for clinical assessment has been developed already, and animal experiment using animal has been performed. An effect on performance of Zerobot caused by deflection of skin and moving body tissue should be confirmed. Therefore experiment with animal is conducted. In this paper, overview of robotic IR and animal puncture experiment are described. Zerobot has sometimes succeeded to insert a needle into animal body tissue. When a needle is inserted to animal, the needle sometimes deflects because animal body tissue is soft. And trajectory of needle is affected by this problem. We can conjecture that this problem occurs also at the time of inserting needle to human. When a needle penetrate surface skin, destruction of spring property of skin was confirmed. In order to detect deflection of needle, magnitude of lateral force is significant. If inclination of lateral force increases along insertion depth, it is expected that the system can predict deflection during inserting needle.