title: Should the automatic exposure control system of CT be disabled when scanning patients with endoaortic stents or mechanical heart valves? A phantom study.
abstract: OBJECTIVE
  To estimate the impact of endoaortic stents/mechanical heart valves on the output of an automatic exposure control (AEC) system and CT radiation dose.
  
  
  METHODS
  In this phantom study, seven stents and two valves were scanned with varying tube voltage (80/100/120 kVp), AEC activation (enabled/disabled) and prosthesis (present/absent), for a total of 540 scans. For each prosthesis, the dose-length product (DLP) was compared between scans with the AEC enabled and disabled. Percentage confidence levels for differences due to the prosthesis were calculated.
  
  
  RESULTS
  Differences between results with the AEC enabled and disabled were not statistically significant (p ≥ 0.059). In the comparison with and without the prosthesis, DLP was unchanged at 80 kVp and 100 kVp, while a slight increase was observed at 120 kVp. The radiation dose varied from 1.8 mGy to 2.4 mGy without the prosthesis and from 1.8 mGy to 2.5 mGy with the prosthesis (confidence level 37-100%).
  
  
  CONCLUSIONS
  The effect of the prosthesis on the AEC system was negligible and not clinically relevant. Therefore, disabling the AEC system when scanning these patients is not likely to provide a benefit.
  
  
  CONCLUSIONS
  • CT-AEC system is not impaired in patients with endoaortic prostheses/heart valves. • Negligible differences may be observed only at 120 kVp. • Disabling the AEC system in these patients is not recommended.
authors.affiliation: Radiology Unit, IRCCS Policlinico San Donato, via Morandi 30, San Donato Milanese, Italy. gianni.dileo77@gmail.com.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Leo
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, Milano, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Spadavecchia
authors.affiliation: Radiology Unit, IRCCS Policlinico San Donato, via Morandi 30, San Donato Milanese, Italy.
authors.forename: Moreno
authors.initials: M
authors.lastname: Zanardo
authors.affiliation: Radiology Unit, IRCCS Policlinico San Donato, via Morandi 30, San Donato Milanese, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Secchi
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, Milano, Italy.|Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Via Celoria 16, Milano, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Veronese
authors.affiliation: Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Via Celoria 16, Milano, Italy.|Dipartimento di Scienze Biomediche, Chirurgiche ed Odontoiatriche, Università degli Studi di Milano, Via Pascal 36, Milano, Italy.
authors.forename: Marie Claire
authors.initials: MC
authors.lastname: Cantone
authors.affiliation: Radiology Unit, IRCCS Policlinico San Donato, via Morandi 30, San Donato Milanese, Italy.|Department of Biomedical Science for Health, Università degli Studi di Milano, via Morandi 30, San Donato Milanese, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sardanelli
mesh_terms: D001011:Aorta / Q000000981:diagnostic imaging / Q000601:surgery; D001807:Blood Vessel Prosthesis; D006350:Heart Valve Prosthesis; D006801:Humans; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000517:prevention & control*; D015607:Stents; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
keywords: Automatic exposure control system; Computed tomography; Endoaortic stents; Mechanical heart valves; Radiation dose