St George's Vascular Institute Protocol: an accurate and reproducible methodology to enable comprehensive characterization of infrarenal abdominal aortic aneurysm morphology in clinical and research applications.
OBJECTIVE
To define the reproducibility of a protocol for the analysis of infrarenal abdominal aortic aneurysm (AAA) morphology for clinical and research purposes.


METHODS
A protocol for the comprehensive assessment of preoperative AAA morphology based on formal systematic review and expert opinion featured 114 morphological parameters (maximum and minimum diameters, cross-sectional areas, vessel lengths, volumes, angulation, and calcification and tortuosity indices) in each of 3 regions: the neck, sac, and access vessels. To validate the protocol, 4 observers measured these variables on the preoperative computed tomographic angiograms from 50 patients (45 men; mean age 75 years, range 52-89) scheduled for endovascular aneurysm repair using software for 3-dimensional image reconstruction. One observer performed repeated measurements. The intra- and interobserver variabilities were calculated for all parameters; measurement time for all 114 features was recorded.


RESULTS
Aortoiliac diameter, length, volume, area, and tortuosity index measurements showed good inter/intraobserver agreement. Aortic neck and aortoiliac angle measurements displayed high intra/interobserver repeatability coefficients (28%-43% and 29%-61%, respectively). Calcification measurements had the highest variability within and between observers: 39%-65% and 44%-96%, respectively. The measurement protocol was completed in a mean 105 minutes (range 55-420).


CONCLUSIONS
Accurate 3-dimensional analysis of AAA morphology can be performed reliably within a reasonable time. Measurements that relied on consistent anatomical landmarks were most reproducible. Assessment of angulation and calcification required a number of subjective judgments, increasing the potential for variation. Automated methods are likely to be more suitable for certain measurements.
Department of Outcomes Research, St George's Vascular Institute, London, UK. ghatwarytmh@yahoo.com
Tamer
T
Ghatwary
Alan
A
Karthikesalingam
Benjamin
B
Patterson
Robert
R
Hinchliffe
Robert
R
Morgan
Ian
I
Loftus
Ayman
A
Salem
Matt M
MM
Thompson
Peter J
PJ
Holt
D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000145:classification* / Q000000981:diagnostic imaging* / Q000601:surgery; D001027:Aortography / Q000379:methods*; D019917:Blood Vessel Prosthesis Implantation; D057510:Endovascular Procedures; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008131:London; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012984:Software; D014057:Tomography, X-Ray Computed; D061205:Vascular Calcification / Q000145:classification / Q000000981:diagnostic imaging