Novel method for real-time hybrid cardiac CT and coronary angiography image registration: visualising beyond luminology, proof-of-concept.

AIMS: During coronary angiography and percutaneous coronary interventions (PCI) only the lumen of the coronary vessel is imaged. The complete pathology of the vessel wall--namely the extent of calcification, structure of non-calcified plaque and lesion length--cannot be accurately determined. These can be imaged using coronary CT angiography (CTCA). We aimed to investigate the accuracy, feasibility, safety and value of a novel hybrid method encapsulating real-time registration of CTCA to coronary angiography images. The method is designed to seamlessly integrate into the routine catheterisation procedures and provide information to assist in decision making during the interventional procedure. METHODS AND
RESULTS: Phantoms simulating the coronary tree were used to test the accuracy and potential of co-registration of information. Precision of the imaging system was tested using radio-opaque markers and distance between bifurcations. We included patients who underwent CTCA and also underwent cardiac catheterisation. Analysis and feasibility was performed offline in the first twenty patients and online in the following 19 patients. The online CTCA and angiography co-registration was performed by the AngioCt software program. The registration result was displayed on a separate screen in the catheterisation laboratory as a three-dimensional coronary tree and a curved multi-planar reformat (MPR) view. Preclinical validation showed that the co-registration of the coronary tree is feasible, and measurements of length and diameter are precise for all standard working angulations during coronary angiography. Real-time registration was successful in all cases and aided in selection of the view that will provide the least foreshortening and no vessel overlapping, the length of balloons and stent to use and assisted in crossing chronic total occlusions (CTO).
CONCLUSIONS: This is the first report of a novel method for online real-time hybrid CTCA and angiography registration. In this pilot study we found that this method is feasible, accurate, and easy to use. It can be used for selecting the best working angulations for minimising foreshortening and vessel overlapping, determining stent size and location, and providing a reference vessel path and structure in cases of CTO.