Spatial Resolution Limits of Multislice Computed Tomography (MS-CT), C-arm-CT, and Flat Panel-CT (FP-CT) Compared to MicroCT for Visualization of a Small Metallic Stent

Abstract

Small metallic stents are increasingly used in the treatment of cerebral aneurysms and for revascularization in ischemic strokes. Realistic three-dimensional datasets of a stent were obtained by using three x-ray-based imaging methods in current clinical use. Multislice-CT (MS-CT), C-arm flat detector-CT (C-arm CT, ACT), and flat panel-CT (FP-CT) were compared with high-resolution laboratory MicroCT scans that served as a reference standard. The purpose was to assess and compare the quality and accuracy of current clinical three-dimensional reconstructions of a vascular stents. A 3 × 20 mm Cypher stent was deployed in a straight polytetrafluoroethylene tube and filled with nondiluted iodine contrast and BaSO(4). MS-CT images of the static tube phantom and stent were acquired using GE LightSpeed VCT Series, C-arm CT images were obtained using Artis (DynaCT, Siemens), FP-CT were obtained using a preclinical research CT (GE), and MicroCT images were obtained using eXplore Locus SP (GE). DICOM datasets were analyzed using Amira and Matlab. Because of blooming effects, the maximum intensity projections (MIPs) and volume renderings generated from MS-CT showed significantly increased strut dimensions with no distinction between the regular struts and connector struts while the lumen diameter is artificially reduced. The shape of the reconstructed stent surface differed remarkably from the real stent. C-arm CT and FP-CT volume renderings more accurately represented the struts. Consistently capturing the structure of the connectors and the strut shape definition was highly threshold dependent. The stent lumen was about 30% underestimated by MS-CT when compared to MicroCT. The spatial resolution of current clinical CT for imaging of small metallic stents is insufficient to visualize fine geometrical details. Further improvement in the spatial resolution of clinical imaging technologies combined with better software and hardware for image postprocessing will be necessary for detailed structural analysis, evaluation of the stent lumen in vivo, and to permit accurate assessment of stent patency and early detection potential in-stent stenosis.