Introduction/Purpose

To explore the value of aneurysmal wall enhancement (AWE) and wall enhancement index (WEI) in vascular wall magnetic resonance imaging (VW-MRI) in the identification of symptomatic and asymptomatic unruptured intracranial aneurysms in Chinese.

Method

Patients were included from October 2014 to July 2019. Vessel wall images (VW-MRI) were acquired at 3T MR in patients with unruptured intracranial aneurysms (UIAs). 2D VW-MRI were collected on a MAGNETOM Skyra/Verio 3T MR scanner (Siemens Healthcare, Erlangen, Germany) with a 16-channel head coil. The scanning parameters of the T1 WI was, with 130 × 130mm field of view, a voxel size of 0.5 × 0.5 × 2mm; a scan comprising 5 slices, a repetition time/echo time of 861/18 ms. The total imaging time was 4 minutes and 55 seconds per sequence. 3D VW-MRI were collected on a MAGNETOM Prisma 3T MR scanner (Siemens Healthcare, Erlangen, Germany) with a 64-channel head coil. The scanning parameters of the three-dimensional sampling perfection with application optimized contrasts using different flip angle evolutions (3D SPACE) was, with 200 × 200 × 200mm field of view, a voxel size of 0.6 × 0.6 × 0.6mm; a scan comprising 224 slices, a repetition time/echo time of 800/14 ms. The total imaging time was 7 minutes and 36 seconds per sequence. Gadopentetate chelate (Magnevist; Bayer HealthCare Pharmaceuticals) was administered intravenously (0.1 mmol/kg), and the 3D SPACE (or T1-weighted imaging sequence) was repeated 5min after the contrast agent was infused. This study included 225 patients (89 symptomatic patients and 136 asymptomatic patients). Each aneurysm was evaluated by two readers to determine whether an AWE was present and its classification according to FAWE and CAWE(Figure 3). Then, quantitative analyses of AWE were performed by two readers to calculate the WEI. The vessel wall and alba signal intensity (SI) was measured by the Vessel-MASS software(Figure 2). The WEI was calculated as follows: ([SIwall/SIbrain on postcontrast imaging]-[SIwall/SIbrain on matched precontrast imaging])/(SIwall/ SIbrain on matched precontrast imaging)1, 2.

Result

This study included 225 patients with 273 UIAs. Inter-reader agreement was excellent for the presence of AWE (k = 0.90 [95% confidence interval: 0.85 to 0.95]), AWE's classification (k = 0.89 [95% confidence interval: 0.84 to 0.93]) and the calculation of WEI (k = 0.97 [95% confidence interval: 0.96 to 0.97]). A CAWE was significantly more frequently observed in symptomatic than in asymptomatic UIAs (59/89, 66.3% versus 32/184, 17.4%, respectively; P = 0.0002). The WEI was significantly higher in symptomatic than in asymptomatic UIAs (1.3 ± 0.8 versus 0.6 ± 0.6, respectively; P < 0.0001). Multivariate logistic regression revealed that CAWE (odds ratio, 28.11; 95% confidence interval, 11.18 to 70.70; P<0.0001) and WEI (odds ratio, 4.99; 95% confidence interval, 3.12 to 7.98; P<0.0001) were the only independent factors associated with symptomatic UIAs. The receiver operating characteristic curve analysis found that the most reliable associated criterion of the WEI to differentiate symptomatic from asymptomatic UIAs was 0.91 (sensitivity, 80.9%; specificity, 71.7%), and the areas under the curve were 0.76 (P<0.0001)(Figure 1).

Discussion

In this study, we found that CAWE and higher WEI were more commonly seen in symptomatic UIAs by using VW-MRI on a large sample of UIAs (about 300 aneurysms)3, 4. This study confirmed that CAWE could identify symptomatic UIAs through qualitative research with a larger sample size, and further confirmed that WEI>0.91 had a sensitivity of 80.9% and specificity of 71.7% in identifying symptomatic UIAs through quantitative methods.

Conclusion

In conclusion, we confirmed CAWE and higher WEI were more commonly seen in symptomatic UIAs. This finding is conducive to risk stratification of UIAs in clinical practice and individualized evaluation of treatment for corresponding Chinese patients.