Reduction of metal artifacts in X-ray computed tomography. Application to vascular imaging in the presence of stents

血管阻塞——由于动脉粥样硬化或其他原因——是一个重要的健康问题，支架放置是一种广泛的治疗方法。为了评估和发现由血栓形成或内膜增生引起的支架内再狭窄，需要对患者进行随访。因此，迫切需要精确且几乎无创的技术来评估支架内的管腔截面。不幸的是，大多数常用的成像方式，包括x射线计算机断层扫描（CT）和磁共振成像，由于支架引起的强金属伪影，结果不佳且不可靠。该项目的目标是开发和验证x射线CT图像重建技术，该技术可以显着减少金属伪影，并应用于血管成像和支架置入后再狭窄评估。该项目将分四个阶段进行：-增强逼真的血管幻象，以便提供插入各种类型支架和模拟不同程度再狭窄的可能性。-开发和验证初始2D x射线CT，该CT将基于导致x射线伪影的现象的准确模型，并且能够合理快速地重建现实尺寸（512x512像素）的图像。-通过开发有效的数值技术和利用重建问题的特殊结构，对方法进行三维扩展和验证。-临床可行性研究，这将构成传播和翻译项目过程中开发的方法的初始阶段。

Blood vessel occlusion - due to atherosclerosis or other causes - is an important health problem for which stent placement is a widespread treatment procedure. Follow-up of the patients is required in order to evaluate and detect in-stent restenosis caused by thrombus formation or neointimal hyperplasia. Therefore, there is a strong need for precise and nearly noninvasive techniques for assessing the lumen cross-section inside the stent. Unfortunately, most commonly available imaging modalities, including X-ray computed tomography (CT) and magnetic resonance imaging, yield poor  and unreliable results due to the strong metal artifacts induced by the stent. The goal of the project is to develop and validate X-ray CT image reconstruction techniques that present significant reduction of metal artifacts, with applications to vascular imaging and restenosis assessment after stent placement. The project will be carried out in four stages: - Enhancement of realistic vascular phantoms, so as to offer the possibility of inserting various types of stents and of modeling various degrees of restenosis. - Development and validation of an initial 2D X-ray CT, that will be based on an accurate model of the phenomena causing X-ray artifacts, and that will be able to reconstruct images of realistic size (512x512 pixels) reasonably fast. - 3D extension and validation of the method by developing efficient numerical techniques and by taking advantage of the special structure of the reconstruction problem. - Clinical feasibility study, that will constitute the initial stage of the dissemination and translation of the methods developed in-the course of the project.