title: Sources of error in the measurement of aortic diameter in computed tomography scans.
abstract: OBJECTIVE
  This study was conducted to determine the differences in the diameter of the thoracic aorta when measured from electrocardiographic (ECG)-gated and nongated computed tomography (CT) angiography. Another aim was to define the difference in the aortic diameter when it is measured at peak systole and end diastole in ECG-gated scans.
  
  
  METHODS
  The gated and nongated CT angiograms of 27 patients (mean age, 58 ± 16 standard deviation [SD] years) obtained on a 256-slice multidetector CT scanner were used. The transverse and anteroposterior diameters and the lumen areas were measured at 1, 4, and 8 cm below the origin of the left subclavian artery.
  
  
  RESULTS
  There was a significant difference in the aortic measurements of diameter between gated and nongated scans found in samples taken at 1, 4, and 8 cm distal to the left subclavian artery (P < .0001). We found a considerable difference between the systolic and diastolic diameters (P < .0001). The maximum change in diameter between systole and diastole was 2.9 ± 0.9 (SD) mm (14.5%, P < .0001) at 1 cm, 5.4 mm (22.6%; median, 1.7 mm; P < .0001) at 4 cm, and 4.4 mm (16.9%; median, 1.3 mm; P < .0001) at 8 cm. There was a significant difference between the transverse and anteroposterior diameters in systole and diastole at all locations (P < .0001): The maximum change in diameter between transverse and anteroposterior diameters in systole was 5.4 ± 1.1 (SD) mm (15.7%, P < .0001) at 1 cm, 5.8 mm (19%; median, 1.4 mm; P < .0001) at 4 cm, and 5 mm (15%; median, 1.02 mm; P < .0001) at 8 cm. There was also a substantial difference between measuring the transverse diameter directly and deriving it from the lumen area (P < .0001).
  
  
  CONCLUSIONS
  Our results showed an important difference between systolic and diastolic diameters measurements in ECG-gated scans. The standard protocol for measuring aortic diameters in gated scans of the thoracic aorta uses images at end diastole because the lack of wall motion at this time provides better resolution. This is likely to result in undersizing that, in some instances, may threaten stability and the proper seal of the stent graft. The dimensions of the aorta in a gated CT should be measured at peak systole rather than the conventional end diastole used today. Most medical centers use nongated CT or gated CT scans in end diastole to calculate sizes of endografts. In view of our findings, the latter method could result in potential complications.
authors: Department of Vascular Surgery, Trinidad Hospital, Buenos Aires, Argentina.
authors: Juan
authors: J
authors: Parodi
authors: Department of Surgery, Section of Vascular Surgery, Samuel and Jean Frankel Cardiovascular Center, University of Michigan, Ann Arbor, Mich; Frankel Vascular Mechanics Laboratory, Department of Biomedical Engineering, University of Michigan, Ann Arbor, Mich. Electronic address: rberguer@umich.edu.
authors: Ramon
authors: R
authors: Berguer
authors: Department of Computed Tomography, Diagnostico Maipu, Buenos Aires, Argentina.
authors: Patricia
authors: P
authors: Carrascosa
authors: Department of Surgery, Section of Vascular Surgery, Samuel and Jean Frankel Cardiovascular Center, University of Michigan, Ann Arbor, Mich; Frankel Vascular Mechanics Laboratory, Department of Biomedical Engineering, University of Michigan, Ann Arbor, Mich.
authors: Khalil
authors: K
authors: Khanafer
authors: Department of Computed Tomography, Diagnostico Maipu, Buenos Aires, Argentina.
authors: Carlos
authors: C
authors: Capunay
authors: Department of Radiology, 3D Imaging Laboratory, University of Michigan, Ann Arbor, Mich.
authors: Eric
authors: E
authors: Wizauer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001027:Aortography / Q000379:methods*; D055424:Cardiac-Gated Imaging Techniques; D003971:Diastole; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013599:Systole; D055815:Young Adult