Laurent Launay

Fully Automatic 3D/2D Subtracted Angiography Registration

Today, 3-D angiography volumes are routinely generated from rotational angiography sequences. In previous work [7], we have studied the precision reached by registering such volumes with classical 2-D angiography images, inferring this matching only from the sensors of the angiography machine. The error led by such a registration can be described as a 3-D rigid motion composed of a large translation and a small rotation.

Quantitative evaluation of an algorithm for correcting geometrical distortions in DSA images: applications to stereotaxy

In digital subtraction angiography, the use of an image intensifier as a detector introduces geometrical distortions in the images. For stereotactic applications, such as the irradiation of cerebral arteriovenous malformations, these distortions have necessarily to be corrected, and the accuracy of this correction has to be examined. As the distortions depend on many parameters that vary during an examination (such as magnetic field and spatial position of the acquisition chain), the correction accuracy must be defined as a function of the acquisition protocol. We have developed a correction method based on the calibration of geometrical distortions using an image of a grid phantom. An experimental study of the influence of acquisition parameters over the distortion has been performed. A protocol has been defined which ensures a correction accuracy of 0.1 millimeter. Finally, we have studied the accuracy obtained in the 3D location of a target as a function of the accuracy of the distortion correction. The final precision allows the use of our method for digital x-ray stereotactic applications.

3D Reconstruction of Cerebral Vessels and Pathologies from a Few Biplane Digital Angiographies

3D reconstructions of cerebral vessels and Arteriovenous Malformations from six digital angiography sequences are compared for three iterative methods, one of them being new. The interest of Multiplicative ART is underlined, and the effects of a criterion minimizing the total density are discussed.

X-ray angiography in stereotactic conditions: techniques and interest for interventional neuroradiology.

This paper reports work in progress on X-ray angiography acquired under stereotactic conditions. The objective is to be able to match multimodality images (typically MRI and X-ray) without a stereotactic frame but with stereotactic precision. We have identified potential problems and have studied them in detail. We conclude that, although the overall application is feasible, much work remains to be done on the estimation of the X-ray system conic projection and on automatic matching based on vascular structures.