Computed rotational angiography: Use of C-arm-mounted XRII for three-dimensional imaging of intracranial vessels during neurointerventional procedures

Recent advances in endovascular therapy for the treatment of cerebrovascular diseases have been made possible mainly through the development of interventional devices and of new techniques for their deployment. Generally, image guidance during procedures such as the treatment of aneurysms using platinum coils is provided by two-dimensional projection images---real-time x-ray fluoroscopy and digital subtraction angiography (DSA). However, quantitative three-dimensional (3D) images could provide benefits for diagnosis, treatment planning and therapy by providing additional information to the interventionalist. We have developed a system capable of providing 3D volume reconstructions during interventional procedures, while preserving the real-time low-dose capability and flexible patient access of the standard DSA system, and called it Computed Rotational Angiography (CRA).;We produced reconstructions using a clinical C-arm mounted X-ray image intensifier (XRII), acquiring 130 projections during an intra-arterial injection of contrast (gantry rotation covered 200° in 4.5 s). Projections were first corrected for angle-dependent distortion in the XRII to within +/-0.1 pixels (global bi-polynomial warp algorithm) and for non-idealities in gantry motion to within +/-0.12 pixels (simple shift algorithm). Three-dimensional volume images were then reconstructed from the corrected projections using a modified conebeam backprojection algorithm.;Vessel signal-difference-to-noise ratio (SNR) in these volumes is limited by artifact from view aliasing, time-varying opacification of vessels and the presence of dense platinum coils. We investigated the relative magnitudes of these artifact sources using a rigid in vitro flow-through model of the intracranial vasculature (vessel diameters known to within +/-0.15 mm; vessel flow within 16% on average of flow specified in the literature) and using an in vivo porcine model including a surgically-created side-wall aneurysm. The SNR was measured as a function of contrast injection rate, blood-flow rate, contrast dilution, and selective injection site. An injection rate of 3 ml/s provided SNR > 25 for all combinations of parameters investigated. Vessel diameters were within +/-6% of the specified phantom values. Platinum coils could be segmented from contrast-filled aneurysms.;We have shown that CRA volumes provide sufficient image quality to characterize vessel, aneurysm, coil and residual neck geometries during interventional procedures.