We face an increasing number of incidentally found aneurysms. However, parameters for personalized risk assessment are rare. In addition to the description of epidemiological and aneurysm geometry features, the first clinical attempts of individualized risk assessment were performed using fluid dynamic simulations [4]. However, in the literature, highly contradicting findings are found, such as high versus low shear stress theories as potential causes for aneurysm rupture [2].

Aneurysm wall thickness (AWT) might serve as another clinical parameter because a histologic examination by Frösen et al. [3] showed that decreasing AWT seems to be closely correlated with increased aneurysm rupture risk. However, few authors have focused on human cerebral AWT measurements. Boussel et al. [1] introduced an indirect method of AWT evaluation by measuring the inner and outer aneurysm volumes in an effort to describe the dangerous progression of fusiform basilar aneurysmal disease. Park et al. [6] assessed the wall of saccular cerebral aneurysms in 14 patients using a 2D double-inversion recovery black-blood sequence (BBDI) at 1.5 T, reporting a resolution of 0.48 × 0.58 × 3 mm³. Although promising, these studies were not without criticism because of perceived methodological shortcomings. Steinmann et al. [10] stated that black-blood imaging is not acceptable for clinical AWT measurements because of its potential for overestimation. They encouraged further ex vivo and in vivo imaging studies to demonstrate the true capabilities and limitations of MR imaging for resolving the wall thickness and morphology of unruptured cerebral aneurysms.

Because of the known limitations of black-blood imaging, we used contrast-enhanced 3D FLASH T1-weighted sequences. 3D sequences were used to minimize partial volume effects. We also found a clear tendency of measurements made from 3-T MR images to overestimate AWT. This overestimation was closely connected to measurement values below the image resolution threshold. Above the image resolution threshold, reasonable values were obtained. Therefore, clinical utility of MR estimates of AWT may be reasonable if measurement ranges defined by the maximum MR resolution are used. In the current study, this would mean a classification of 0–0.4, 0.41–0.8, 0.81–1.2 mm, etc. Additionally, a combination of AWT measurements with shear stress simulations could lead to a better understanding of the interactions between flow-related physical forces and aneurysm wall reactions.