title: Evaluation of low-dose CT angiography with model-based iterative reconstruction after endovascular aneurysm repair of a thoracic or abdominal aortic aneurysm.
abstract: OBJECTIVE
  The objective of our study was to evaluate image quality and overall adequacy of low-dose CT angiography (CTA) with model-based iterative reconstruction (MBIR) in patients who had undergone endovascular aneurysm repair (EVAR) of a thoracic or abdominal aortic aneurysm.
  
  
  METHODS
  Thirty patients, all of whom had undergone standard-dose CTA performed previously with adaptive statistical iterative reconstruction (ASIR), underwent low-dose CTA for surveillance after EVAR. Two radiologists randomly evaluated both studies, and quality parameters were assessed. The maximal aneurysm diameter was measured, and the images were evaluated to see whether an endoleak was present. The image noise and contrast-to-noise ratio (CNR) were measured. The volume CT dose index and dose-length product were recorded.
  
  
  RESULTS
  The mean image score for low-dose CTA was acceptable to very good in all categories of assessment. There was no significant difference between low-dose CTA and standard-dose CTA in the evaluation of the stent lumen. Subjective assessments of stent configuration, aneurysm outline, aortic branch vessel outline, overall adequacy of vascular imaging, and overall adequacy of solid organ imaging were superior on standard-dose CTA. Interobserver agreement for endoleak detection was higher for low-dose CTA. There was no significant difference in the mean aneurysm diameter between the two readers on low-dose CTA and standard-dose CTA. The effective radiation dose for low-dose CTA was lower than standard-dose CTA during both the arterial (mean, 4.4 vs 16.2 mSv, respectively) and the delayed (2.4 vs 6.7 mSv) phase acquisitions. The measured image noise was lower (14.7 vs 19.3 HU) and CNR was higher (25.6 vs 17.1) on the low-dose CTA studies than on the standard-dose CTA studies.
  
  
  CONCLUSIONS
  Low-dose CTA with MBIR enables up to 73% dose reduction as compared with CTA performed with ASIR while maintaining diagnostic adequacy for CTA surveillance of patients who have undergone EVAR of a thoracic or abdominal aortic aneurysm.
authors.affiliation: 1 Department of Radiology, University of Nebraska Medical Center, 981045 Nebraska Medical Center, Omaha, NE 68198-1045.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Hansen
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Kaza
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Maturen
authors.forename: Peter S
authors.initials: PS
authors.lastname: Liu
authors.forename: Joel F
authors.initials: JF
authors.lastname: Platt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001014:Aortic Aneurysm / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery*; D057867:Endoleak / Q000000981:diagnostic imaging* / Q000209:etiology*; D057510:Endovascular Procedures / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome