Double Your Views - Exploiting Symmetry in Transmission Imaging

TL;DR

This paper extends the concept of symmetry exploitation from optical to transmission imaging, proposing a method to estimate symmetry planes and generate virtual views to improve data completeness and motion compensation in imaging.

Contribution

It introduces the first algorithm to estimate 3-D symmetry planes in transmission imaging and demonstrates how to exploit symmetry for virtual view generation and motion correction.

Findings

Successfully estimated symmetry planes from projection images.

Generated virtual trajectories to enhance data completeness.

Validated approach on synthetic and real head phantom scans.

Abstract

For a plane symmetric object we can find two views - mirrored at the plane of symmetry - that will yield the exact same image of that object. In consequence, having one image of a plane symmetric object and a calibrated camera, we can automatically have a second, virtual image of that object if the 3-D location of the symmetry plane is known. In this work, we show for the first time that the above concept naturally extends to transmission imaging and present an algorithm to estimate the 3-D symmetry plane from a set of projection domain images based on Grangeat's theorem. We then exploit symmetry to generate a virtual trajectory by mirroring views at the plane of symmetry. If the plane is not perpendicular to the acquired trajectory plane, the virtual and real trajectory will be oblique. The resulting X-shaped trajectory will be data-complete, allowing for the compensation of in-plane motion using epipolar consistency. We evaluate the proposed method on a synthetic symmetric phantom and, in a proof-of-concept study, apply it to a real scan of an anthropomorphic human head phantom.