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A new system for rotational x-ray angiograms to create 3-D images of the coronary arteries could supplant angiography if the results from the first-in-human experience hold-up larger clinical trials.

Results of a 23-patient feasibility trial of the new 3D x-ray angiography system developed by Philips Healthcare and researchers at the University  of Colorado-Denver, with first author Dr Anne M Neubauer (University of Colorado, Denver), are published in Circulation:Cardiovascular  Interventions. The study compared standard 2D angiogram images with 3D angiogram images from the same patient to evaluate the 3D system's ability to create high-quality images, visualize coronary lesions, and support quantitative coronary analysis (QCA).

The study "highlights the potential of an x-ray-based fully automatic, gated, iterative reconstruction approach for providing clinically useful and accurate 3D volumetric images of the coronary arteries for use in percutaneous coronary interventions," study coinvestigator Dr Joel Garcia (University of Colorado, Denver) told. "These first-in-human results of the 3D reconstruction set the stage for the next step and welcome evolution of x-ray -based in-lab evaluations."

Two-thirds of the 3D images were deemed by surveyed interventionalists as having high image quality and providing additional clinical information not available in the 2D images, such as complete visualization of bifurcations or other views of the coronary tree otherwise unobtainable. The true-positive lesion-detection rates for each patient were between 90% and 100%, while the false-positive rates were under 10%. The 3D QCA showed significantly similar lumen diameters and vessel segment length as the 2D QCA, without the errors of foreshortening that can sometimes arise from 2D visualization.

Traditional single-view, 2D x-ray angiography is the primary technique for imaging coronary artery disease, but the limitations of flat images sometimes hinder the accurate assessment of diseased vessels and lesions. In that case 3D x-ray angiography can be used.

Standard angiography relies on the operator to acquire multiple views of suspect vessel segments with a "trial-and-error technique" to optimize visualization, Neubauer and colleagues explain. In an attempt to reduce operator dependence, some interventionalists have shifted to a rotational angiography technique in which the x-ray C-arm is programmed to rotate during continuous contrast injection to acquire many images of the coronary tree during a single acquisition. However, this method "still requires that the operator mentally fuse the multiple 2D images to generate a 3D impression."

The system evaluated in this trial is designed to completely remove the operator-dependent steps by automating the construction of the 3D images from the images taken by the rotating C-arm with continuous contrast injection, the authors explain.

Garcia explained that the key to developing the 3D system has been creating software algorithms that can compensate for the motion of the heart with image "gating" techniques and optimization of the cardiac "face selection."

Currently, computed tomography ( CT ) can produce images of the coronary arterial tree superior to those created by standard coronary angiography, especially for the imaging of vessel features such as eccentric plaques, vessel tortuosity, bifurcation angles, foreshortening, and vessel overlap, Garcia said. However, "our group aims at generating CT -quality 3D reconstructions of the coronaries based on x-ray angiograms during the procedure," he said.

Because 3D x-ray angiography equipment is already ubiquitous, "generating three-dimensional information from the x-ray data itself may represent the most accessible and cost-effective approach for the interventional laboratory," Garcia said.

The system tested in this trial constructed the 3D images offline, and the study did not include clinical end points. Garcia cautioned that this is just a preliminary trial and the potential for this type of 3D imaging to improve interventionalists' "in-room" clinical decision-making impact on clinical practice still needs to be evaluated.

"The results justify the further development of this technique and the in-room use and testing in a larger group of patients who are likely to need an intervention," the authors conclude. "Further studies incorporating the in-room evaluation of the reconstructed 3D data are needed to answer questions that impact contrast volume, radiation exposure, laboratory workflow, coronary intervention performance, and other important clinical outcome measures."

Neubauer and study coauthors Dr Eberhard Hansis and Gert Schoonenberg work for divisions of Philips. Philips Healthcare funded the study.

Source: University of Colorado, Denver

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