TU‐F‐CAMPUS‐I‐02: Contrast Enhanced Cone Beam CT Imaging with Dual‐ Gantry Image Acquisition and Constrained Iterative Reconstruction‐a Simulation Study for Liver Imaging Application

Abstract

Purpose:Contrast time‐density curves may help differentiate malignant tumors from normal tissues or benign tumors. Repetitive scans using conventional CT or cone beam CT techniques, which Result in unacceptably high dose, may not achieve the desired temporal resolution. In this study we describe and demonstrate a 4D imaging technique for imaging and quantifying contrast flows requiring only one or two 360° scans.Methods:A dual‐gantry system is used to simultaneously acquire two projection images at orthogonal orientations. Following the scan, each or both of the two 360° projection sets are used to reconstruct an average contrast enhanced image set which is then segmented to form a 3D contrast map. Alternatively, a pre‐injection scan may be made and used to reconstruct a pre‐injection image set which is subtracted from the post‐injection image set to form the 3D contrast map. Each of the two 360° projection sets is divided into 12 subsets, thus creating 12 pairs of 30° limited angle projection sets, each corresponding to a time spanning over 1/12 of the scanning time. Each pair of the projection sets are reconstructed as a time specific 3D image set with the maximum likelihood estimation iterative algorithm using the contrast map as the constraint. As a demonstration, a 4D abdominal phantom was constructed from clinical CT images with blood flow through the normal tissue and a tumor modeled and imaging process simulated.Results:We have successfully generated a 4D image phantom, and calculated the projection images. The time density curves derived from the reconstructed image set matched well with the flow model used to generate the phantom.Conclusion:Dual‐gantry image acquisition and constrained iterative reconstruction algorithm may help to obtain time‐density curves of contrast agents in blood flows, which may help differentiate malignant tumors from normal tissues or benign tumors.