In vivo quantification of murine aortic cyclic strain, motion, and curvature: implications for abdominal aortic aneurysm growth.
OBJECTIVE
To develop methods to quantify cyclic strain, motion, and curvature of the murine abdominal aorta in vivo.


METHODS
C57BL/6J and apoE(-/-) mice underwent three-dimensional (3D) time-of-flight MR angiography to position cardiac-gated 2D slices at four locations along the abdominal aorta where circumferential cyclic strain and lumen centroid motion were calculated. From the 3D data, a centerline through the aorta was created to quantify geometric curvature at 0.1-mm intervals. Medial elastin content was quantified with histology postmortem. The location and shape of abdominal aortic aneurysms (AAAs), created from angiotensin II infusion, were evaluated qualitatively.


RESULTS
Strain waveforms were similar at all locations and between groups. Centroid motion was significantly larger and more leftward above the renal vessels than below (P < 0.05). Maximum geometric curvature occurred slightly proximal to the right renal artery. Elastin content was similar around the circumference of the vessel. AAAs developed in the same location as the maximum curvature and grew in the same direction as vessel curvature and motion.


CONCLUSIONS
The methods presented provide temporally and spatially resolved data quantifying murine aortic motion and curvature in vivo. This noninvasive methodology will allow serial quantification of how these parameters influence the location and direction of AAA growth.
Goergen
Craig J
CJ
Department of Bioengineering, Stanford University, Stanford, California 94305-5431, USA. cgoergen@stanford.edu
Barr
Kyla N
KN
Huynh
Diem T
DT
Eastham-Anderson
Jeffrey R
JR
Choi
Gilwoo
G
Hedehus
Maj
M
Dalman
Ronald L
RL
Connolly
Andrew J
AJ
Taylor
Charles A
CA
Tsao
Philip S
PS
Greve
Joan M
JM
D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D001012:Aorta, Abdominal / Q000503:physiopathology*; D017544:Aortic Aneurysm, Abdominal / Q000503:physiopathology*; D001057:Apolipoproteins E / Q000235:genetics; D004549:Elastin / Q000378:metabolism; D005838:Genotype; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009038:Motion; D013997:Time Factors
D001057:Apolipoproteins E; D000804:Angiotensin II; D004549:Elastin