A system and method for tracking completeness of co-registered medical image data is disclosed herein. The system and method tracks the position of an anatomical reference marker positionable on a patient and an ultrasound probe during an imaging session and co-registers medical images based on positional data received from the anatomical reference marker and the ultrasound probe. Using the co-registered image data, the system and method generates a surface contour of a region of interest (ROI) of the patient, such as a breast. The surface contour is defined to represent an interface between a chest wall structure and tissue of the ROI in a plurality of co-registered medical images. A completeness map of the image data within the defined surface contour during the imaging session is generated and overlaid on a graphic representation of the ROI.