PROCEEDINGS ARTICLE | July 20, 2015
Proc. SPIE. 9415, Medical Imaging 2015: Image-Guided Procedures, Robotic Interventions, and Modeling
KEYWORDS: Surgery, Calibration, Ultrasonography, Image segmentation, Image processing, Error analysis, Robotics, Image acquisition, Transducers, Image-guided intervention
Image-guided surgery systems are often used to provide surgeons with informational support. Due to several unique
advantages such as ease of use, real-time image acquisition, and no ionizing radiation, ultrasound is a common
intraoperative medical imaging modality used in image-guided surgery systems. To perform advanced forms of guidance
with ultrasound, such as virtual image overlays or automated robotic actuation, an ultrasound calibration process must be
performed. This process recovers the rigid body transformation between a tracked marker attached to the transducer and
the ultrasound image. Point-based phantoms are considered to be accurate, but their calibration framework assumes that
the point is in the image plane. In this work, we present the use of an active point phantom and a calibration framework
that accounts for the elevational uncertainty of the point. Given the lateral and axial position of the point in the
ultrasound image, we approximate a circle in the axial-elevational plane with a radius equal to the axial position. The
standard approach transforms all of the imaged points to be a single physical point. In our approach, we minimize the
distances between the circular subsets of each image, with them ideally intersecting at a single point. We simulated in
noiseless and noisy cases, presenting results on out-of-plane estimation errors, calibration estimation errors, and point
reconstruction precision. We also performed an experiment using a robot arm as the tracker, resulting in a point
reconstruction precision of 0.64mm.
