A Flexible Ultrasound Scanning System for Minimally Invasive Spinal Surgery Navigation

Minimally invasive surgery has become the primary treatment of spine disease. It depends on high-precision medical image as guidance. Ultrasound imaging is expected to replace X-ray fluoroscopy as a golden standard scheme of minimally invasive spinal surgeries. Researchers make effort to develop ultrasound imaging for the process of navigation, taking its distinctive advantages of user-friendly and radiation-free. However, it is greatly affected by the contact force and incident angle of the probe, which depends a lot on experienced sonographers. To this end, a flexible ultrasound scanning system (FUSS) is proposed to automatically image the human spine. In mechanics, a flexible fixture, fixed on the end joint of robotic arm, is designed to ensure the ultrasound probe to be pressed against the dorsal skin. Besides, decoupled control strategy is presented which decouples trajectory planning task and force control task into separate joint space. By this means, the possibility of accidental damage could be minimized. Phantom experiments were carried out to validate the hysteresis characteristic of flexible fixture, the capacity to resisting impact, the performance of control system and the quality of reconstruction image. These results show that our system has high safety performance and could keep the probe force stable within the range of 1 N to obtain better reconstruction image than freehand scanning. In summary, it has a great potential on navigation of spine surgery.