title: Time-resolved computed tomography imaging of the aorta: a feasibility study.
abstract: OBJECTIVE
  The aim of this study was to test the feasibility and the additional value of time-resolved computed tomography angiography (CTA) of the aorta, using multiple low-dose phases.
  
  
  METHODS
  Twenty-two consecutive patients underwent a time-resolved CTA protocol (TR-CTA) of the aorta, either for follow-up of endovascular aneurysm repair (EVAR) or aortic dissection, using a CT scanner with the possibility of bidirectional table movements for dynamic CT imaging (Siemens Definition AS+; 12 phases, temporal resolution 2.5 s/scan, 80 kVp, 120 mAs/rot, scan range 27 cm, 60 mL; Imeron 400, flow 5.0 mL/s). The patients had previously undergone standard CTA (120 kVp, 100 mL contrast agent). Standard CTA after EVAR and aortic dissection were triphasic and biphasic protocols, respectively. Effective radiation dose and maximum Hounsfield unit values were compared between the TR-CTA and standard CTA. Image quality was rated for TR-CTA.
  
  
  RESULTS
  Fifteen patients underwent TR-CTA for follow-up after EVAR; 4 were examined for follow-up after dissection and 3 for both, that is, aortic dissection treated with an endovascular stent. Mean effective dose of TR-CTA for the scan range of 27 cm (15.3+/-1.1 mSv) was comparable with the biphasic standard CTA protocols (16.2+/-2.4 mSv; P=0.29). Triphasic protocols resulted in 23.7+/-4.9 mSv (P<0.0001). Hounsfield unit values were not significantly different. Most of the examinations (91%) were fully evaluable, whereas 9% were of limited evaluability because of high image noise. None of the examinations was nondiagnostic.
  
  
  CONCLUSIONS
  TR-CTA consisting of multiple low-dose phases leads to a clear depiction of the angiographic information and is feasible for follow-up after EVAR and aortic dissection. Considering the limited scan range, radiation dose is comparable with the standard biphasic CTA protocol, but dynamic information may provide additional information.
authors.affiliation: Department of Clinical Radiology, University Hospitals-Grosshadern, Ludwig-Maximilians University, Munich, Germany. wieland.sommer@med.uni-muenchen.de
authors.forename: Wieland H
authors.initials: WH
authors.lastname: Sommer
authors.forename: Dirk A
authors.initials: DA
authors.lastname: Clevert
authors.forename: Fabian
authors.initials: F
authors.lastname: Bamberg
authors.forename: Andreas
authors.initials: A
authors.lastname: Helck
authors.forename: Edda
authors.initials: E
authors.lastname: Albrecht
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Christoph R
authors.initials: CR
authors.lastname: Becker
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
mesh_terms: D000368:Aged; D000784:Aortic Dissection / Q000000981:diagnostic imaging* / Q000601:surgery; D001014:Aortic Aneurysm / Q000000981:diagnostic imaging* / Q000601:surgery; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D018709:Statistics, Nonparametric; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media