Improving the temporal response of computed tomography fluoroscopy

Interventional procedures with the guidance of computed tomography have attracted significant interest among clinicians in recent years. The application of computed tomography fluoroscopy (CTF) to interventional procedures has not only significantly improved the patient safety and reduced the probability of procedure complication, but also significantly shortened the procedure time. Recent studies, however, have indicated that a significant time delay exists in the CTF due to the nature of tomographic reconstruction process. This inherent limitation could lead to either confusions to the operator or prolonged interventional procedure time. A detailed comparison of various tomographic reconstruction algorithms indicates that the halfscan algorithm provides one of the best performance in terms of time delay. To further improve the temporal response of the CTF system, we propose an optimized halfscan (OHS) algorithm. The OHS algorithm suppresses information at the start of the scan by applying non-positive weights to the projections. At the same time, the projections near the end of the scan are given weights larger than unity. The weighting function is designed such that the overall contribution from the redundant samples remains constant. The parameters of the weighting function are selected to achieve a proper balance between the temporal response of the system and the acceptable level of image artifacts. Theoretical analysis and phantom experiments have shown that a significant improvement in CTF temporal response can be achieved with the proposed scheme.