Clinical Imaging Study Of Rupture Risk Prediction Of Intracranial Saccular Unruptured Aneurysms By 3T Magnetic Resonance Imaging

Part I Association of aneurysm wall permeability with rupture risk of unruptured intracranial saccular aneurysms using dynamic contrast-enhanced MRIBackground and Purpose-Individual assessment of rupture risk of intracranial aneurysm (IA) is still challenging, and increased knowledge of predictors for IA rupture is needed. Recently, the permeability of IA wall quantified by dynamic contrast-enhanced MRI (DCE-MRI) has been proposed to predict IA progression. However, the relationship of IA wall permeability with other risk factors and its value in IA rupture risk assessment are unknown. Thus, the purpose of this study is to investigate the relationship of IA wall permeability with established clinical/imaging risk factors and explore its potential in IA rupture prediction.Methods-After institutional ethics approval and obtained informed consent,32 patients with unruptured saccular IAs diagnosed by DSA were recruited and imaged with DCE-MRI. The transfer constant (Ktrans), which reflects IA wall permeability was calculated and compared against established imaging and clinical metrics, such as IA maximum size, IA wall enhancement, location, multiplicity, blebs, and patient demographics, such as gender, hypertension, smoking and diabetes. As to the patients with conservative treatment, the former calculated Ktrans in the ruptured and unruptured patients were compared. Routine DCE-MRI follow-up was performed for unruptured aneurysms at the interval of 6 months after the first examination.Results-Three patients were excluded for DCE analysis for the cavernous sinus corruption after contrast injection. Of the remaining 29 patients (16-74 years; 22 females), IA wall permeability were larger than the reference (0.0428±0.0380min-1 vs.0.0033±0.0017min-1, P<0.001). In addition, Ktrans was weakly correlated with IA size (R2=0.24, P<0.01). For the relationship between IA wall permeability and AWE, higher Ktrans (P=0.036) were found in patients with AWE (n=19) compared with patients without AWE (n=10). As to the 9 patients with conservative treatments,2 patients died from aneurysmal intracranial hemorrhage and the Ktrans in the 2 ruptured patients were significantly larger than the 7 unruptured cases (P<0.01). Follow-up DCE-MRI was obtained in four patients, only one patient manifested increase of Ktrans, while Ktrans in the other 3 patients remained stable.Conclusions-We found aneurysm Ktrans which was elevated from healthy artery, correlated positively with size, and was higher in group of wall enhancement. Furthermore, IA Ktransof ruptured patients were significantly higher than the nonruptured. Therefore, IA wall permeability is a potential imaging marker for IA rupture risk prediction, while larger sample size is needed to validate it.Part II Aneurysmal Wall Enhancement in Unruptured Intracranial Aneurysms using Contrast-enhanced Black Blood MRIBackground and Purpose-Aneurysmal wall enhancement (AWE) has emerged as a new imaging marker for depicting the inflammation of intracranial aneurysm (IA). However, the relationships of AWE with the established risk factors are still unclear for unruptured IAs. The purpose of this study was to investigate the association between AWE and the established risk metrics in unruptured IAs.Methods-Forty-eight patients with unruptured saccular IAs diagnosed by digital subtraction angiography were recruited. AWE was evaluated using the pre-and post-contrast black blood MR images. Univariate and multivariate logistic analyses were performed to investigate the association of AWE with the morphology factors, including IA size, neck width, parent vessel diameter, location, multiplicity, daughter sacs, and other clinical factors. Prevalence of AWE was also reported and compared in different IA size groups.Results-Sixty-one aneurysms were detected. Aneurysm size was found to be an independent risk factor associated with AWE (OR 2.46 per mm increase,95% CI 1.34-4.51; P=0.004). Patient age was independently and inversely associated with AWE (OR 0.898 per year increase,95% CI 0.812-0.994; P=0.037). Higher prevalence of AWE was observed in larger aneurysms, while 12%(3/25) IAs with size less than 7mm exhibited AWE.Conclusions-AWE was independently associated with aneurysm size in unruptured intracranial aneurysms. Although AWE was more frequently observed in larger IAs, considerable portion of small aneurysms did exhibit wall enhancement, suggesting that AWE may provide additional instability information of aneurysm to improve current size based rupture risk evaluation metric.