Assessment of thoracic aortic dimensions in an experimental setting: comparison of different unenhanced magnetic resonance angiography techniques with electrocardiogram-gated computed tomography angiography for possible application in the pediatric population.
OBJECTIVE
To compare different unenhanced magnetic resonance angiography (MRA) techniques for quantitative evaluation of vessel lumen in an experimental setting in young pigs whose dimensions allow for a comparison with a pediatric population.


METHODS
Magnetic resonance imaging was performed in 5 healthy ventilated pigs at 1.5 T. Three different electrocardiogram (ECG)-triggered sequences were applied for MRA: [TSE-Db] T2-weighted dark-blood TurboSpinEcho (2.0 x 1.1 x 4 mm3); [trueFISP] 2D-steady-state-free-precession (2.2 x 1.8 x 2 mm3); [NAV] respiratory-gated, T2-prepared 3D-trueFISP (1.3 x 1.3 x 1.3 mm3). ECG-gated-CT angiography (CTA) (16-row CT, 1 mm collimation) served as the standard of reference. The vessel lumen was measured at 7 positions perpendicularly angulated to the vessel wall on multiplanar reformations: ascending aorta (P1), the aortic arch before (P2) and after (P3) the origin of the first supraaortic branch, the aortic arch after the origin of the second supraaortic branch (P4), the descending aorta at the level of the diaphragm (P5), and the first and second supraaortic branches (P6, P7).


RESULTS
Percentage differences in the vessel area determined by MRA reformation compared with CTA-reformation were 10% +/- 20% and 35% +/- 27% (TSE-Db), -4% +/- 13% and 20% +/- 24% (trueFISP), and -3% +/- 13% and -10% +/- 19% (NAV), for positions P1 to P5 and P6 to P7, respectively. A significant difference from CTA was found for TSE-Db at all positions, and for trueFISP only at positions P6 and P7.


CONCLUSIONS
Unenhanced MRA techniques allow for a reliable assessment of the dimensions of the thoracic aorta compared with CTA as the standard of reference. Using ECG-gating and navigator techniques, the free-breathing approach showed the best agreement with CTA. This technique may therefore be the most useful in the pediatric age group allowing for true 3D data acquisition with its inherent postprocessing possibilities.
Ley-Zaporozhan
Julia
J
Department of Radiology (E010), German Cancer Research Center, Heidelberg, Germany. juliazapo@web.de
Kreitner
Karl-Friedrich
KF
Unterhinninghofen
Roland
R
Helm
Emma
E
Puderbach
Michael
M
Schenk
Jens-Peter
JP
Deshpande
Vibhas
V
Krummenauer
Frank
F
Szabo
Gabor
G
Kauczor
Hans-Ulrich
HU
Ley
Sebastian
S
D000818:Animals; D001013:Aorta, Thoracic / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D002648:Child; D003287:Contrast Media; D004562:Electrocardiography / Q000379:methods; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media