Clinical CT applications such as oncology follow-up using iodine maps require accurate contrast agent (CA)
quantification within the patient. Unfortunately, due to beam hardening, the quantification of CA materials like iodine in
dual energy systems can vary for different patient sizes and surrounding composition. In this paper we present a novel
method that handles this problem which takes into account properly the CA energy dependent attenuation profile. Our
method is applicable for different dual energy scanners, e.g. fast kVp switching or dual layer detector array and is fully
compatible with image domain material analysis. In this paper we explain the concept of so called landmarks used by our
method, and give the mathematical formulation of how to calculate them. We demonstrate by scans of various phantom
shapes and by simulations, the robustness and the accuracy of the iodine concentration quantification obtained by our
method.
A novel approach is presented which combines rotational X-ray imaging, real-time fluoroscopic X-ray imaging and real-time catheter tracking for improved guidance in interventional electrophysiology procedures. Rotational X-ray data and real-time fluoroscopy data obtained from a Philips FD10 flat detector X-ray system and are registered with real-time localization data from catheter tracking equipment. The visualization and registration of rotational X-ray data with catheter location data enables the physician to better appreciate the underlying anatomy of interest in three dimensions and to navigate the interventional or mapping device more effectively. Furthermore, the fused information streams from rotational X-ray, real-time X-ray fluoroscopy and real-time three-dimensional catheter locations offer a direct imaging feedback during interventions, facilitating navigation and potentially improving clinical outcome. With the technique one is able to reduce the fluoroscopic time required in a procedure, since the catheter is registered and visualized with off-line projection data from various view angles. We show a demonstrator which integrates, registers, and visualizes the various data streams. It can be implemented in the clinical work-flow with reasonable effort. Results are presented based on an experimental setup. Furthermore, the robustness and the accuracy of this technique have been determined based on phantom studies.
Cone beam reconstructed cardiac CT images suffer from characteristic streak artifacts that affect the quality of coronary artery imaging. These artifacts arise from inhomogeneous distribution of noise. While in non-tagged reconstruction inhomogeneity of noise distribution is mainly due to anisotropy of the attenuation of the scanned object (e.g. shoulders), in cardiac imaging it is largely influenced by the non-uniform distribution of the acquired data used for reconstructing the heart at a given phase. We use a cardiac adaptive filter to reduce these streaks. In difference to previous methods of adaptive filtering that locally smooth data points on the basis of their attenuation values, our filter is applied as a function of the noise distribution of the data as it is used in the phase selective reconstruction. We have reconstructed trans-axial images without adaptive filtering, with a regular adaptive filter and with the cardiac adaptive filter. With the cardiac adaptive filter significant reduction of streaks is achieved, and thus image quality is improved. The coronary vessel is much more pronounced in the cardiac adaptive filtered images, in slab MIP the main coronary artery branches are more visible, and non-calcified plaque is better differentiated from vessel wall. This improvement is accomplished without altering significantly the border definition of calcified plaques.
Fast 16-slice spiral CT delivers superior cardiac visualization in comparison to older generation 2- to 8-slice scanners due to the combination of high temporal resolution along with isotropic spatial resolution and large coverage. The large beam opening of such scanners necessitates the use of adequate algorithms to avoid cone beam artifacts. We have developed a multi-cycle phase selective 3D back projection reconstruction algorithm that provides excellent temporal and spatial resolution for 16-slice CT cardiac images free of cone beam artifacts.
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