The course and the success of an endovascular intervention can be influenced by the choice of the guidewire and primary by its ability to access to the lesion. The simulation of catheterism in complex vasculature is of main interest to aid the surgery planning. The overall objective of the simulation is to improve the choice of guidewire (with the simulation of its intrinsic features: torque, shape, rigidity, elasticity) as well as its navigation within patient specific vasculature. We propose a new approach for the simulation of guidewire navigation. It is based on: (i) the modeling of guidewire using "multi-body" approach and the representation of its internal characteristics, (ii) the modeling of artery as a surface mesh, (iii) the simulation of the interactions of the guidewire with its environment (artery and clinician). In this study, strength and elasticity of the guidewire are modeled. Only the "push" action performed by the clinician is considered. The global behavior of the guidewire is simulated by means of retraction and relaxation processes. To interact with the artery walls, methods based on the graphics hardware have been developed (i) to detect the collisions between the guidewire and the artery walls (ii) to find the direction of the retraction process which define the local reaction of the guidewire. All these methods have been tested in a qualitative validation on a patient vasculature.
The aim of conformal radiation therapy and of radiosurgery (Gamma Knife and Multi-beam radiosurgery) is to irradiate the pathological target volume with ionizing radiation while avoiding as well as possible the surrounding normal tissues. Recently, new micro multileaf collimator ((mu) MLC) devices are available for conformal therapy. A (mu) MLC is formed by narrow sliding leafs in such a manner that the irradiation field can be adjusted to the shape of the target. It is interesting to compare the different techniques to evaluate their effectiveness and their accuracy. This comparison involves 8 clinical cases. For each treatment modality, we compare indexes defined in the international literature by the Radiation Therapy Oncology Group (RTOG). This theoretical study shows (i) the interest of the use of intensity modulation in the case of conformal radiation therapy and (ii) the improvement of RTOG indexes with using the conformal radiotherapy although the volumes of irradiated normal tissue remains lower with the radiosurgery than those with the (mu) MLC. However the comparison between these three techniques for the brain tumors shows that in complex cases it is more effective to use the fractionated conformal therapy with intensity modulation instead of radiosurgery. It is already sure that the micro multileaf collimator holds an important place in conformal therapy.
KEYWORDS: 3D modeling, Image registration, Distance measurement, Angiography, Tomography, Magnetic resonance angiography, Medical imaging, Algorithm development, Digital imaging, Gold
This study proposes a new method for matching vascular imaging modalities without the use of external frame or external landmarks. We first perform a 3D reconstruction of a piece of the cerebral vascular tree using Magnetic Resonance Angiography (MRA). Then, this structure is projected on the Digital Subtracted Angiography (DSA) images until its best position and orientation are found. As the 3D structure is known in the MRA referential, this method enables us to match information from DSA and MRA. The complete matching of all the DSA images in many incidences and the MRA set have been obtained. For the DSA images, the epipolar constraint has been verified between all the incidences. This new approach in medical imaging brings a very original method, making easier and more efficient visualization and quantification of vascular information.
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