title: Comparison of visibility for four self-expanding nitinol bare stents in vitro.
abstract: BACKGROUND
  Sufficient radiopacity of stents is a prerequisite for safe interventions and minimization of the radiation dose for the patient and the interventionist. Modern nitinol stents are considered less radiopaque compared to formerly used stents.
  
  
  OBJECTIVE
  To evaluate the objective detection rate (ODR) and the subjective radiopacity score (SRS) of four self-expanding nitinol stents with their markers on a phantom human pelvis.
  
  
  METHODS
  We evaluated the ODR (as a percentage of correctly identified stents) and the SRS (on a scale from 0 = not visible to 4 = excellent visibility) for four self-expanding nitinol stents (SinusSuperflex, SMART, Luminexx, Zilver) with 8 mm diameter and 40 mm length. Stents were placed on a phantom human pelvis and images of the stents were taken in four different positions (right and left lumbosacral joint and near the right and left limbus acetabuli) using the following modes: spotfilm, pulsed fluoroscopy (4, 7.5, 15, and 30 pulses/min) and at three different digital magnification modes. Dose area products (DAPs) were assessed.
  
  
  RESULTS
  ODR and SRS, respectively, were significantly increased for the SMART stent compared to all other tested stents (P < 0.05): SMART 93.53% and 2.43, SinusSuperflex 90.81% and 2.21, Luminexx 90.39% and 2.20, and Zilver 89.28% and 2.21. ODR was significantly reduced in position 3 where the bone overlap was more pronounced for all stents (detection rates 77.14-79.56%). An increase in magnification significantly improved the ODR and SRS for all stents (70.33-99.25% and 1.07-3.28, respectively, P < 0.05). Increased pulsing frequency did not improve the ODR of the various stents but did increase the DAP.
  
  
  CONCLUSIONS
  The SMART stent had the best overall performance. In the presence of bone overlap, all self-expanding nitinol stents had poor results. Increased pulsing frequency did not improve ODR or SRS but did increase the DAP. Use of digital magnification modes had no effect on DAP increasing ODR and SRS.
authors.affiliation: Division of Diagnostic Radiology, Department of Radiology, University of Tübingen, Bielefeld, Germany. Benjamin.wiesinger@med.uni-tuebingen.de
authors.forename: Benjamin
authors.initials: B
authors.lastname: Wiesinger
authors.forename: Alexander
authors.initials: A
authors.lastname: Stütz
authors.forename: Jörg
authors.initials: J
authors.lastname: Schmehl
authors.forename: Gerd
authors.initials: G
authors.lastname: Groezinger
authors.forename: Claus Detlef
authors.initials: CD
authors.lastname: Claussen
authors.forename: Jakub
authors.initials: J
authors.lastname: Wiskirchen
mesh_terms: D000497:Alloys; D017130:Angioplasty / Q000295:instrumentation*; D005471:Fluoroscopy; D006801:Humans; D066298:In Vitro Techniques; D010388:Pelvis; D019047:Phantoms, Imaging; D011474:Prosthesis Design; D011829:Radiation Dosage; D018709:Statistics, Nonparametric; D015607:Stents
chemical_list: D000497:Alloys; C013616:nitinol