Brief reportAutomated Quantification of Aortoaortic and Aortoiliac Angulation for Computed Tomographic Angiography of Abdominal Aortic Aneurysms before Endovascular Repair: Preliminary Study
Section snippets
Algorithm
At our institution, the angulation of the aorta and iliac arteries at four anatomic locations are measured manually by technologists for every patient with an infrarenal aortic aneurysm. Measurements of angulation are provided at (1) the level of the superior boundary of the aneurysm sac (termed the ”proximal neck angle”), (2) the middle of the aneurysm sac (termed the ”aneurysm angle”), and (3) each common iliac artery origin (termed the ”common iliac artery angle”) for a total of four angles.
Results
Figure 5 shows the correlations between automatically measured and known angles in the ”virtual phantoms,” with R2 values of 0.99 in all cases and slopes very close to 1. Over all phantoms and angles, the mean error between the actual and measured angles was 0.7 degrees ± 0.5 (standard deviation). The P value for Schuirmann's two one-sided equivalence test was less than .05, allowing us to reject the null hypothesis and conclude that there was no statistically significant difference between
Discussion
Manual measurement of aortoiliac angulation may be excessively variable (6, 7, 10). Clinically significant variability has also been reported in manual measurements of angulation using CT in other structures, such as in extremities (8, 14) and pulmonary veins (9). The interobserver variability of manual measurements in this article is slightly less than that reported by Diehm et al (approximately 6 degrees vs approximately 13 degrees, 20% vs 32%) (10). This reduction in variability could be due
Acknowledgment
The authors are grateful to Carl R. Crawford, PhD, for providing the core of the CT scanner simulation software used for validating this algorithm.
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Cited by (7)
Aortic Curvature Remodeling after Thoracic Endovascular Aortic Repair: Assessing Device Conformability, Using Image Vector Analysis
2019, Annals of Vascular SurgeryCitation Excerpt :In the thoracic aorta, in spite of the thicker walls, larger diameter, more angulated angles, and higher flows, and dynamic forces, authors of some previous publications pointed out that after placement of an aortic endograft, the aortic curvature could be remodeled. However, important biases were associated: manual rendering and measuring in 2D (not 3D) examinations,3–5 analysis of dissections with confusions with true and false lumens,6 no intraobserver and interobserver agreements, … Admitting all these biases, progressive remodeling of the aorta subsequent to placement of an endograft was observed with a softening of aortic curvature (increase of intra-aortic angulation) during the follow-up.6 Following this line, our group previously published an analysis of aortic curvature remodeling one month after TEVAR (mainly with Relay endografts: Bolton Medical, Sunrise, FL, USA), with an accurate 2D and 3D center lumen line (CLL) analysis after division of the aortic lumen into different segments.7
Interobserver and intraobserver variability in measuring the tortuosity of the thoracic aorta on computed tomography
2018, Journal of Vascular SurgeryPreoperative Planning of Endovascular Procedures in Aortic Aneurysms
2017, Computing and Visualization for Intravascular Imaging and Computer-Assisted StentingAortic Arch and Thoracic Aorta Curvature Remodeling after Thoracic Endovascular Aortic Repair
2017, Annals of Vascular SurgeryCitation Excerpt :Measurements (CLL and point identification) were manually performed, with the obvious expected errors that could be made, but excellent intraobserver and interobserver variability were seen, which minimizes this error source. We assumed that all patients lay straight on the CTA table, without tilts or rotations, and pre- and post-CTA were directly comparable; an endeavor to correct this possible angulation bias was previously attempted (corrections depending on bone marks, i.e., the scapula edge), but aberrant results were obtained and this effort was declined, assuming correct and similar positions in the CTA table (like previous published studies).3,4,8,9 In this study, we did observe a change in the aortic arch angulation after TEVAR, which, itself, may involve long-term implications and flow pattern changes into the aortic arch; however, we did not observe immediate complications related to these changes, so there is not a palpable and immediate practical application of our work.
Centerline is not as accurate as outer curvature length to estimate thoracic endograft length
2013, European Journal of Vascular and Endovascular SurgeryCitation Excerpt :This outer curvature length is not the real length of the outer aortic wall and is consequently independent of the size of the aneurysmal sac or the presence of thrombus. We used a calculated index of tortuosity based on the reporting standard for thoracic endovascular aortic repair.4,5 This was defined as the ratio between the centerline and the straightline lengths.
This research was supported by National Institutes of Health grants 5RO1HLO58915 and 1RO1HL67194. None of the authors have identified a conflict of interest.