Ultrasound is garnering significant interest as an imaging modality for surgical guidance, due to its affordability,
real-time temporal resolution and ease of integration into the operating room. Minimally-invasive intracardiac
surgery performed on the beating-heart prevents direct vision of the surgical target, and procedures such as
mitral valve replacement and atrial septal defect closure would benefit from intraoperative ultrasound imaging.
We propose that placing 4D ultrasound within an augmented reality environment, along with a patient-specific
cardiac model and virtual representations of tracked surgical tools, will create a visually intuitive platform with
sufficient image information to safely and accurately repair tissue within the beating heart. However, the quality
of the imaging parameters, spatial calibration, temporal calibration and ECG-gating must be well characterized
before any 4D ultrasound system can be used clinically to guide the treatment of moving structures. In this paper,
we describe a comprehensive accuracy assessment framework that can be used to evaluate the performance of 4D
ultrasound systems while imaging moving targets. We image a dynamic phantom that is comprised of a simple
robot and a tracked phantom to which point-source, distance and spherical objects of known construction can be
attached. We also follow our protocol to evaluate 4D ultrasound images generated in real-time by reconstructing
ECG-gated 2D ultrasound images acquired from a tracked multiplanar transesophageal probe. Likewise, our
evaluation framework allows any type of 4D ultrasound to be quantitatively assessed.