Volume-preserving correction of non-rigid registrations for the investigation of pleural thickening growth

摘要

Pleural thickenings can be assessed using 3D CT-image data. A precise registration in the thickening regions is required for a detailed investigation of the volumetric thickening growth and to algorithmically combine image information from two points in time. For this purpose, a non-rigid registration, utilizing B-spline based deformations, is applied. This kind of deformation is computationally efficient; however it might induce volumetric compression in the image domain. For the assessment of growth, it is inevitable to guarantee volume-preservation. In this paper we suggest a new method to enforce this preservation during the registration process in selected image regions. In contrast to other volume-preserving approaches, this correction is independent of the preliminary chosen method to estimate the non-rigid registration. To reduce complexity in large scale cases, we additionally present a method to approximate the global correction by successively solving smaller sub-tasks. Finally we show that both methods reduce the compression induced by the deformation and also enhance the registration quality in terms of image similarity.