Determining x-ray projections for coil treatments of intracranial aneurysms.

The endovascular coil embolization of intracranial saccular aneurysms requires a set of specific X-ray images with which to view the aneurysm during coiling. These two-dimensional (2-D) images, known as working projections, should be optimal for measuring the aneurysm sac diameter, inserting the first coil, and checking coil overhang into the surrounding vessels. At present the gantry tilt that produces these images is found by the radiologist by trial and error. In this paper, we present a method for automatically finding the angles that will produce the desired X-ray projections. Our method consists of four steps: 1) finding the location and orientation of the aneurysm neck; (2) labeling the aneurysm sac; 3) determining the optimal tilts for viewing the aneurysm during coiling; and 4) adjusting the optimal tilts for change in the patient orientation between pre-Guglielmi detachable coil (GDC) scanning and the coiling treatment. We discuss these steps and present results of the algorithm applied to pathological examples in the form of simulated X-ray images. A final discussion is given for one example where our results have been applied in a clinical situation.