TU-AB-201-12: Effects of Tissue Interference On Electromagnetic Sensor and Ultrasound Imaging Sensing for Robot-Guided Needle Interventions

Abstract

Purpose: To quantify the effects of tissue interference on electromagnetic (EM) sensing and ultrasound (US) imaging feedback modalities for controlling a robot-guided medical needle interventions. Methods: First, the experimental set up to control the robot-guided needle insertion with and without tissue interference involving 6-DOF EM (Aurora, NDI, Waterloo, Canada) sensory feedback is constructed. Next, the experimental set up has been modified to replace EM sensory feedback with the bi-planer US imaging (Flex Focus 800, BK Medical, Peabody, MA) feedback. In both these experimental feedback cases the control task is to guide the needle intervention (vertically downwards to avoid the gravitational pull on the needle) as per the desired trajectory. For EM sensory feedback the thickness of the tissue used for interference is 90mm whereas for the US imaging feedback, the thickness is reduced to 25 mm as the needle was not visible from 90mm to 26 mm. Performance repeatability is assessed in five observations for each experiment. Results: The mean and standard deviation (SD) of the root mean square error (RMSE) value for the tracking performance using EM sensory feedback with no tissue interference are 0.10mm and 0.01mm, respectively. With tissue interference, these values are 0.14mm and 0.01mm. Corresponding mean RSME and SD with and without tissue interference using the US imaging modality are 0.15 mm (SD=0.02mm) and 0.41mm (SD=0.04mm), respectively. Conclusion: Experimental results reveal that there exists significant difference (p=0.0001) between the tracking performances with and without tissue interference using US imaging feedback. Whereas for the EM sensory feedback, there exists no significant difference (p=0.0576) between with and without tissue interference RMSE values. However, both the sensing modalities may be suitable for needle-based clinical applications. More rigorous study involving both EM and US feedback modalities in various soft tissue phantoms are in progress. Acknowledgement: Research supported by DoD (Grant#W81XWH-11-1-0397/98/99)