title: Evaluation of noninvasive follow-up methods for the detection of intracranial in-stent restenosis: a phantom study.
abstract: OBJECTIVE
  Intra-arterial digital subtraction angiography (IA-DSA), an invasive procedure, is the current reference examination after percutaneous transluminal angioplasty and stenting for the detection of in-stent restenosis (ISR). In this phantom study, we evaluated flat-panel angiographic computed tomography after intravenous contrast agent application (IV-ACT) and multidetector computed tomographic angiography (MDCTA) as potential noninvasive follow-up alternatives after intracranial percutaneous transluminal angioplasty and stenting.
  
  
  METHODS
  We simulated an intracranial vessel using a silicon tube placed inside a human skull. Three different stent systems were deployed inside the silicon tubes, each with diameters of 3 or 4 mm. Three grades of ISR (25%, 50%, and 75%) were simulated. The IA-DSA and IV-ACT examinations were performed on a flat-panel detector angiography system. The MDCTA images were acquired with a 128-slice computed tomographic scanner. The mean stenosis diameters, measured with each technique, were compared using the Bland-Altman plot. The difference between the known stenosis diameter and the measured stenosis diameter was calculated for each examination.
  
  
  RESULTS
  Stenosis measurements on the IA-DSA images showed no statistically significant differences compared with the known stenosis diameters (P = 0.19). In the 3-mm stent category, when compared with the known stenosis diameter, mean (SD) differences of 0.01 (0.15) mm, 0.03 (0.24) mm and 0.16 (0.5) mm were calculated for the IA-DSA, IV-ACT, and MDCTA stenosis measurements, respectively. As for the 4-mm stents, IA-DSA and IV-ACT were again very accurate, with mean (SD) differences of -0.03 (0.11) mm and 0.07 (0.19) mm, respectively, compared with the known stenosis diameters, whereas MDCTA overestimated ISR, with a mean (SD) difference of 0.49 (0.53) mm. The Bland-Altman plots show a mean (SD) difference of 0.08 (0.2) mm between IA-DSA and IV-ACT (95% confidence interval, 0.05-0.11) and a mean (SD) difference of 0.34 (0.56) mm between IA-DSA and MDCTA measurements (95% confidence interval, 0.25-0.42).
  
  
  CONCLUSIONS
  In our phantom study, IA-DSA was the only examination to predict accurately degrees of stenosis compared with the known stenosis diameters. The results of the IV-ACT measurements were comparable with those of IA-DSA. Multidetector computed tomographic angiography was less accurate in the quantification of stenosis, usually overestimating ISR.
authors.affiliation: Department of Neuroradiology, University Medicine Goettingen, Goettingen, Germany. m.psychogios@med.uni-goettingen.de
authors.forename: Marios-Nikos
authors.initials: MN
authors.lastname: Psychogios
authors.forename: Peter
authors.initials: P
authors.lastname: Schramm
authors.forename: Nadine
authors.initials: N
authors.lastname: Amelung
authors.forename: Sara-Magdalena
authors.initials: SM
authors.lastname: Pilgram-Pastor
authors.forename: Klaus
authors.initials: K
authors.lastname: Gröschel
authors.forename: Katrin
authors.initials: K
authors.lastname: Wasser
authors.forename: Andreas Maximilian
authors.initials: AM
authors.lastname: Frölich
authors.forename: Alexander
authors.initials: A
authors.lastname: Mohr
authors.forename: Michael
authors.initials: M
authors.lastname: Knauth
mesh_terms: D001157:Arterial Occlusive Diseases / Q000000981:diagnostic imaging*; D001921:Brain / Q000098:blood supply*; D002533:Cerebral Angiography / Q000379:methods*; D003251:Constriction, Pathologic / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D012008:Recurrence; D015607:Stents; D014057:Tomography, X-Ray Computed