title: CT angiography in stent-graft sizing: impact of using inner vs. outer wall measurements of aortic neck diameters.
abstract: OBJECTIVE
  To assess the impact of using inner wall vs. outer wall measurements on stent-graft sizing for endovascular repair of abdominal aortic aneurysm (AAA).
  
  
  METHODS
  Preoperative static and electrocardiographically-gated 64-slice computed tomographic angiography (CTA) datasets were acquired on 40 consecutive AAA patients (29 men; mean age 78.9 ± 6 years, range 75-89). On static images, the aortic neck diameters were manually measured twice by 2 readers at 3 clinically relevant levels (supra-, juxta-, and infrarenal). The measurements were obtained from intima-to-intima (inner wall) and from adventitia-to-adventitia (outer wall). Dynamically reconstructed scans were also reviewed in each phase of the cardiac cycle to identify inner and outer minimum/maximum diameters. Using inner and outer wall measurements performed on static images, readers selected the size of a stent-graft that required inner neck diameter measurements and then one that required outer wall diameters. To calculate the relative oversizing, each selected stent-graft size was compared to that obtained using dynamic measurements. Oversizing <4% or >30% was considered inadequate.
  
  
  RESULTS
  Mean variations for the inner and outer wall diameters of 9.75% ± 4.01% and 8.66% ± 3.71%, respectively, were recorded on static CTAs; the absolute changes in diameters were 1.82 ± 0.63 mm and 1.91 ± 0.64 mm, respectively. No statistically significant differences were found relative to aortic pulsatility at the 3 levels in the neck for the inner or outer wall diameters. Significant variability was seen between inner (mean 20.8 ± 3.4 mm) vs. outer (mean 23.7 ± 4.3 mm; p < 0.05) wall diameters. Stent-graft sizes significantly changed on the basis of the measurement method and device; for example, using the outer diameter to size a stent-graft that requires an inner diameter reference changed 36% of the selected stent-graft sizes, with ~20% being excessively oversized. Conversely, using the inner diameter to size an outer-diameter-based stent-graft resulted in nearly 40% of the sizes being altered. Based on dynamic measurements, the changes were more dramatic: the oversizing was considered excessive in up to 90% of patients if the measurement method did not match the stent-graft's stipulated reference.
  
  
  CONCLUSIONS
  These data suggest that stent-graft sizing should follow the manufacturer's recommendations for using inner or outer diameter references based on dynamic patterns (mean value between diastolic and systolic diameters suggested).
authors.affiliation: Department of Bioimaging and Radiological Sciences, Institute of Radiology, Catholic University, Rome, Italy. iezzir@virgilio.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Iezzi
authors.forename: Roberta
authors.initials: R
authors.lastname: Dattesi
authors.forename: Federica
authors.initials: F
authors.lastname: Pirro
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Nestola
authors.forename: Marco
authors.initials: M
authors.lastname: Santoro
authors.forename: Francesco
authors.initials: F
authors.lastname: Snider
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bonomo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D001027:Aortography / Q000379:methods*; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D055424:Cardiac-Gated Imaging Techniques; D003287:Contrast Media; D004562:Electrocardiography; D057867:Endoleak / Q000209:etiology / Q000517:prevention & control; D057510:Endovascular Procedures / Q000009:adverse effects / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007479:Iopamidol / Q000031:analogs & derivatives; D007558:Italy; D008297:Male; D015588:Observer Variation; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011474:Prosthesis Design; D011673:Pulsatile Flow; D015203:Reproducibility of Results; D015607:Stents; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; C057937:iomeprol; D007479:Iopamidol