Aneurysm Volume-to-Ostium Area Ratio: A Parameter Useful for Discriminating the Rupture Status of Intracranial Aneurysms
ABSTRACT Slow or stagnant flow is a hemodynamic feature that has been linked to the risk of aneurysm rupture.
To assess the potential value of the ratio of the volume of an aneurysm to the area of its ostium (VOR) as an indicator of intra-aneurysmal slow flow and, thus, in turn, the risk of rupture.
Using a sample defined from internal databases, a retrospective analysis of aneurysm size, aspect ratio (AR), and VOR was performed on a series of 155 consecutive aneurysms having undergone 3-dimensional digital subtraction angiography as a part of their evaluation. Measurements were obtained from 3-dimensional digital subtraction angiography studies using commercial software. Aneurysm size, AR, and VOR were correlated with rupture status (ruptured or unruptured). A multiple logistic regression model that best correlated with rupture status was generated to evaluate which of these parameters was the most useful to discriminate rupture status. This model was validated using an independent database of 62 consecutive aneurysms acquired outside the retrospective study interval.
VOR showed better discrimination for rupture status than did size and AR. The best logistic regression model, which included VOR rather than size or AR, determined rupture status correctly in 80.6% of subjects. The reproducibility calculating AR and VOR was excellent.
Determination of VOR was easily done and reproducible using widely available commercial equipment. It may be a more robust parameter to discriminate rupture status than AR.
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ABSTRACT: To our knowledge, no reproducible animal model of a giant bifurcation type aneurysm has been described. It was our aim to develop a 1-stage and reproducible model of a venous pouch giant aneurysm in canines. Nine canines were involved. Bilateral CCAs were exposed. The left CCA was divided and its distal segment was swung to the right side. Using the right CCA and the distal segment of the left CCA, either a bifurcation or a terminal arterial structure was constructed. Bilateral external jugular veins were also exposed. A 30-mm vein segment was harvested from each side. Each vein graft was split and unfolded to make 2 venous sheets. These sheets were then joined top-to-bottom so as to form a single cylinder in such a way that original adventitial side of the venous sheets was on the exterior surface. In 2 instances, pieces of polytetrafluoroethylene were employed along with the venous sheets. The combined vein graft was then incorporated into the arterial anastomosis. Lastly, the top of the venous pouch was closed. No medications for anticoagulant or antiplatelet were used throughout the study period. Follow-up imaging studies were performed. It took 2.5 hours on average for 2 operators to create an aneurysm. Eight of the 9 aneurysms were patent at follow-up. The cause of the spontaneous thrombosis was unclear despite autopsy. All the aneurysms had a maximum diameter >20 mm. We demonstrated and illustrated a 1-stage and reproducible procedure to create a model of a venous pouch bifurcation giant aneurysm in canines.American Journal of Neuroradiology 12/2011; 33(3):507-12. DOI:10.3174/ajnr.A2789 · 3.68 Impact Factor
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ABSTRACT: Numerous size and shape parameters have historically been used to describe cerebral aneurysms and to correlate rupture status. These parameters are often inconsistently defined. To evaluate the impact of definition variation on rupture status detection performance. Catheter rotational angiographic data sets of 134 consecutive aneurysms (60 ruptured) were automatically measured in 3 dimensions with a validated algorithm. According to the literature, aneurysm height was assessed as both maximal and orthogonal distances from dome to neck. Maximal and orthogonal widths were defined perpendicular to height definitions. Neck size was evaluated as minimum, maximum, and average diameter of the neck plane. Aspect ratio (AR; height/neck), height/width ratio (HW), and bottleneck factor (BNF; width/neck) were evaluated for alternative definitions of each size variable. Univariate statistics were used to identify significant features and to compute the area under the curve (AUC) of the receiver-operating characteristic. The AR, HW, and BNF showed significant dependence on parameter definition. Statistical significance and performance varied widely, depending on alternative definitions: AR, AUC range of 0.59 to 0.75; HW, AUC range of 0.48 to 0.72; and BNF, AUC range of 0.57 to 0.72. Using maximal height, orthogonal width, and minimum neck resulted in the best AR, HW, and BNF performances. Compared with HW, AR and BNF were less sensitive to alternative definitions. Alternative aneurysm size definitions have a significant impact on prediction performance and optimal threshold values. Adoption of standard methodology and sizing nomenclature appears critical to ensure rupture detection performance and reproducibility across studies.Neurosurgery 02/2012; 71(1):38-46. DOI:10.1227/NEU.0b013e3182503bf9 · 3.03 Impact Factor
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ABSTRACT: Geometric indices defined on intracranial aneurysms have been widely used in rupture risk assessment and surgical planning. However, most indices employed in clinical settings are currently evaluated based on two-dimensional images that inevitably fail to capture the three-dimensional nature of complex aneurysmal shapes. In addition, since measurements are performed manually, they can suffer from poor inter and intra operator repeatability. The purpose of the current work is to introduce objective and robust techniques for the 3D characterization of intracranial aneurysms, while preserving a close connection to the way aneurysms are currently characterized in clinical settings. Techniques for automatically identifying the neck plane, key aneurysm dimensions, shape factors, and orientations relative to the parent vessel are demonstrated in a population of 15 sidewall and 15 terminal aneurysms whose surface has been obtained by two trained operators using both level-set segmentation and thresholding, the latter reflecting typical clinical practice. Automatically-identified neck planes are shown to be in concordance with those manually positioned by an expert neurosurgeon, and automatically-derived geometric indices are shown to be largely insensitive to segmentation method or operator. By capturing the 3D nature of aneurysmal sacs and by minimizing observer variability, our approach allows large retrospective and prospective studies on aneurysm geometric risk factors to be performed using routinely acquired clinical images.Annals of Biomedical Engineering 04/2012; 40(10):2188-211. DOI:10.1007/s10439-012-0577-5 · 3.23 Impact Factor