Revealing in-stent stenoses of the iliac arteries: Comparison of multidetector CT with MR angiography and digital radiographic angiography in a phantom model

OBJECTIVE. Our objective was to evaluate the detectability of in-stent stenoses in iliac artery stents; using multidetector CT angiography in comparison with MR angiography and digital radiographic angiography. MATERIALS AND METHODS. Ten different metallic stents (made of steel, nitinol, tantalum, or cobalt) were implanted in plastic tubes (8 nun). The stent lumina were partially obstructed by wax (CT density, -30 H) resulting in 50-60% in-stent stenoses. The tubes were filled with diluted contrast material (25 mmol/L of gadopentetate dimeglumine or 6 mg I/mL of iodinated contrast material) and placed in a plastic container filled with oil or water, respectively. CT angiography was performed on a four-detector CT scanner (detector collimation, 4 x 1 mm; slice thickness, 1.25 mm; table feed, 4 mm per rotation). MR angiography was performed on a 1.5-T system with a three-dimensional gradient-echo sequence (TR/TE, 4.6/1.8; flip angle, 30degrees; slice thickness, 1.88 nun). Axial and longitudinal reformations of CT and MR imaging data were evaluated regarding the in-stent attenuation and signal intensity, the visible lumen diameter inside the stent, and the delineation of the stenoses. For comparison, digital radiographic angiography was performed as the gold standard. RESULTS. The degree and character of stent-related artifacts differed in CT angiography and MR angiography. In CT angiography, only the tantalum stent caused artifacts that obscured the stenosis; in all other cases, the stenoses were visible. In MR angiography, depiction of stenoses was impaired in two steel stents but possible in the tantalum and most nitinol stents. CONCLUSION. CT angiography is suited for detection of relevant stenoses in steel, cobalt-based, and nitinol stents. MR angiography is superior only in tantalum products.