Patient-specific AAA wall stress analysis: 99-percentile versus peak stress.
OBJECTIVE
Biomechanically, rupture of an Abdominal Aortic Aneurysm (AAA) occurs when the stress acting on the wall due to the blood pressure, exceeds the strength of the wall. Peak wall stress estimations, based on CT reconstruction, may be prone to observer variation. This study focuses on the robustness and reproducibility of AAA wall stress assessment and the relation with geometrical features of the AAA.


METHODS
The AAAs of twenty patients were reconstructed by three operators. Both the peak and 99-percentile stress were used for intra- and inter-operator variability using the intraclass correlation coefficient (ICC). A regression analysis was performed to relate the stress parameters with the maximum diameter. Outliers were analyzed by their geometrical characteristics.


RESULTS
The intra-operator ICC was 0.73-0.79 for the peak stress and 0.94 for the 99-percentile stress. The inter-operator ICC was 0.71 for the peak stress and 0.95 for the 99-percentile stress. A significant linear relation with the diameter was found only for the 99-percentile stress.


CONCLUSIONS
The 99-percentile stress is more reproducible than peak wall stress. A significant relation between wall stress and diameter was found. Other geometrical features had no statistical relation with high stress.
Eindhoven University of Technology, Department of Biomedical Engineering, Maastricht, The Netherlands. l.speelman@tue.nl
L
L
Speelman
E M H
EM
Bosboom
G W H
GW
Schurink
F A M V I
FA
Hellenthal
J
J
Buth
M
M
Breeuwer
M J
MJ
Jacobs
F N
FN
van de Vosse
D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data