title: Small-vessel stents for intracranial angioplasty: in vitro comparison of different stent designs and sizes by using CT angiography.
abstract: OBJECTIVE
  Our purpose was to evaluate whether CT angiography is a suitable alternative to conventional angiography in the evaluation of small-vessel stents for intracranial angioplasty.
  
  
  METHODS
  CT angiographic appearances of 23 stents of different designs and sizes (2.0, 3.0, and 4.0 mm) were investigated after they were filled with a solution of 0.9% NaCl or diluted contrast medium. For each stent, artificial lumen narrowing (ALN) was measured, and the difference in the number of pixels with a Hounsfield value below 200 HU between the two filling states, DIFF(HU<200), was calculated to provide an objective indicator of the size of the evaluable stent diameter.
  
  
  RESULTS
  With a window width of 1500 HU at a window level of 400 HU, ALN ranged from 66.8% to 97.7% in the group of 2.0-mm stents and from 38.6% to 66.8% in the groups of 3.0- and 4.0-mm stents. For the 2.0-mm stents, DIFF(HU<200) was zero. In the groups of 3.0- and 4.0-mm stents, DIFF(HU<200) ranged from 0.3 to 6.7, corresponding to a diameter of 0.13-3.0 mm, when the pixel size was presupposed to be 0.449 mm.
  
  
  CONCLUSIONS
  CT angiographic evaluation of small-vessel patency after stent placement is considerably impaired by ALN. Stent manufacturers should be aware of potential artifacts caused by their stents during noninvasive diagnostic studies such as CT angiography.
mesh_terms: D000800:Angioplasty, Balloon / Q000295:instrumentation*; D001921:Brain / Q000098:blood supply*; D002533:Cerebral Angiography; D019544:Equipment Failure Analysis; D006801:Humans; D019047:Phantoms, Imaging; D011474:Prosthesis Design; D017755:Prosthesis Fitting; D012306:Risk; D014057:Tomography, X-Ray Computed