Co-registration of a needle-positioning device with a volumetric x-ray micro-computed tomography scanner for image-guided preclinical interventions

An apparatus and method are developed for integration of a needle- positioning robot with volumetric micro-computed tomography image guidance for interventions in small animals. Accurate registration is critical for integration as it enables targets identified in the image to be mapped to physical coordinates inside the animal. Registration is accomplished by injecting barium sulfate into needle tracks created in a tissue-mimicking phantom. Registration accuracy is therefore affected by the positioning error of the robot and is assessed by measuring the point-to-line target registration error (TRE). Centroid points along cross-sectional slices of the track are determined using region growing segmentation followed by application of a center-of-mass algorithm. The centerline points are registered to needle trajectories in robot coordinates by applying an iterative closest point algorithm between points and lines. Implementation of this procedure with four fiducial needle tracks produced a point-to-line TRE of 194 plusmn 18 mum.