Planning of intravascular brachytherapy based on virtual exploratory navigation in x-ray CT images

In most planning procedures of intravascular brachytherapy the lesion path is assumed to be a straight line and the dose distribution is essentially specified with respect to the seed. We propose a new approach for the planning of peripheral intravascular brachytherapy based on the characterization of the vessel by virtual exploratory navigation. In order to make the procedure more secure and reliable, the dosimetry planning takes actually account of the geometrical characteristics of the vessel (length, diameter, curvature). Virtual exploratory navigation constitutes the basis of optimal path planning (centering, positioning, trajectory definition) and dosimetry planning for high dose rate brachytherapy. In order to estimate the post-angioplasty vessel centerline and inner surface, a simplified simulation of the transluminal angioplasty procedure is performed using a single pre-angioplasty CT data set. Thanks to the dose rate computation performed in the whole CT volume, the irradiation of the surrounding anatomical structures can be anticipated. A virtual angioscopy like process is used to check the homogeneity of the dose distribution in the vessel wall. Preliminary results obtained from a phantom model and from an animal model of stenosis are reported.