Detection of the optimal reconstruction window for respiratory-gated micro-CT imaging

Abstract

The aim of this study was to detect the optimal data window used for respiratory-gated micro-CT imaging improving image quality with respect to motion blurring. A dedicated algorithm was adapted to the micro-CT system providing retrospective phase-correlated image reconstruction for respiratory gating. We applied a rawdata-based motion function (kymogram) to micro-CT projection data identifying the respiratory motion cycle. The kymogram function was used for synchronization purposes and for the identification of the optimal data window used for phase-correlated image reconstruction. A motion index was assessed using the kymogram function indicating phase intervals of increased and decreased motion and allowing for the detection of the optimal reconstruction phase. Measurements were performed on a dual-source micro-CT scanner. Projection data were acquired over ten rotations for multi-segment phase-correlated reconstruction. Visual assessment was performed on datasets of ten free-breathing subjects. The kymogram function provides a synchronization signal correlated to the respiratory motion and enables application to phase-correlated image reconstruction. Phase-correlated images showed a strong improvement with respect to motion blurring compared to standard image reconstruction. A reconstruction for the predicted optimal data window provided least amount of motion blurring and even allowed for the assessment of small structures in the lung. The dedicated retrospective phase-correlated image reconstruction procedure for respiratory gating is a feasible approach for motion-free imaging. The subject-specific optimal reconstruction phase can minimize motion blurring and has the potential to further improve image quality. © 2009 Springer-Verlag.