REGISTRATION OF THREE-DIMENSIONAL HIGH-FREQUENCY ULTRASOUND IMAGES TO A ROBOTIC NEEDLE-POSITIONING SYSTEM FOR PRE-CLINICAL RESEARCH

A needle-positioning robot has been developed for high-frequency ultrasound guided interventions into mouse models. In order for the robot to reach targets identified in ultrasound accurately, the robot and ultrasound image coordinate systems must be registered. Registration is accomplished by attaching a phantom, which contains 280 mum diameter fiducials, onto the robot end-effector. The positions of the fiducials with respect to the needle were measured using micro-CT to determine the location of the fiducials in robot coordinates. The fiducial positions were also located in ultrasound coordinates. Point-based rigid-body and affine transformations were calculated between the two coordinate systems. For the rigid-body transformation, the target registration error (TRE) was 74 mum. For the affine transformation, the TRE was 56 mum. The smaller TRE of the affine registration will reduce the overall error of performing image-guided interventions in mice compared to using a rigid-body registration