Purpose:To characterize the relationship between aneurysm size and epidemiologic risk factors with growth and rupture by using computed tomographic (CT) angiography.
Materials and Methods:In this HIPAA-compliant, institutional review board approved study, patients with known asymptomatic unruptured intracerebral aneurysms were followed up longitudinally with CT angiographic examinations. Growth was defined as an increase in one or more dimensions above the measurement error, and at least 5% volume by using the ABC/2 method. Associations of epidemiologic factors with aneurysm growth and rupture were analyzed by using logistic regression analysis. Intra-and interobserver agreement coefficients for dimension, volume, and growth were evaluated by using the Pearson correlation coefficient and difference of means with 95% confidence intervals, the agreement statistic, and the McNemar x 2 .
Results:Patients (n = 165) with aneurysms (n = 258) had a mean follow-up time of 2.24 years from time of diagnosis. Forty-six of 258 (18%) aneurysms in 38 patients grew larger. Spontaneous rupture occurred in four of 228 (1.8%) intradural aneurysms of average size (6.2 mm). Risk of aneurysm rupture per patient-year was 2.4% (95% CI: 0.5%, 7.12%) with growth and 0.2% (95% CI: 0.006%, 1.22%) without growth (P = .034). There was a 12-fold higher risk of rupture for growing aneurysms (P , .002), with high intra-and interobserver correlation coefficients for size, volume, and growth. Tobacco smoking (3.806, one degree of freedom; P , .015,) and initial size (5.895, two degrees of freedom; P , .051) were independent covariates, predicting 78.4% of growing aneurysms.
Conclusion:These results support imaging follow-up of all patients with aneurysms, including those whose aneurysms are smaller than the current 7-mm treatment threshold. Aneurysm growth, size, and smoking were associated with increased rupture risk. Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. Patients underwent follow-up CT angiographic examinations (16-64 detectors) at intervals of approximately 6 or 12 months. The scan protocol was standardized with the following parameters: kVp, 120; mA, 250-300; section thickness, 0.6-1.0 mm; reconstruction interval, 0.5 mm; matrix size, 512 3 512; field of view, 180 mm; soft-tissue kernel; injection rate, 3 mL per second of iohexol (Omnipaque 350; GE Healthcare, Milwaukee, Wis) and bolus triggering software with a carotid artery threshold of 150 HU. Axial oblique two-dimensional multiplanar reformatted grayscale images (window width = 450 HU, window level = 150 HU) were analyzed to obtain the length 3 width 3 height of the aneurysm sac relative history of subarachnoid hemorrhage has not been clearly established.Many investigators believe that all patients with aneurysms should receive follow-up to monitor for the possibility of growth or other signs of impending rupture, such as a bleb (9). The tradit...