Diagnostic Value Of Outflow Angle Measurement In Evaluating Sidewall Cerebral Aneurysms Based On 3D-TOF MRA

Objective:To evaluate the application value of an outflow angle?OA?–assisted approach on the diagnosis of sidewall cerebral aneurysms?SCAs?and the differenciation of small aneurysms with infundibula.Methods:First,from June 2007 to July 2015,60 patients were randomly selected from 438 patients with integrated images of DSA and 3.0 MRA of SCAs and other cerebrovascular diseases.Four OA(OA1 _beginning,OA2 _milddle,OA3 _{golden section,}and OA4 _end)was measured on MRA to calculate the accuracy,sensitivity and specificity for the diagnosis of the SCAs.An OA?90°indicated a SCA,while an OA<90°did not.Secondly,OA which was measured as the midpoint of the aneurysm neck in 438 patients associated with the sujective approach were used to evaluate the accuracy,sensitivity and specificity for the diagnosis of the SCAs.Digital subtraction angiography?DSA?was regarded as the gold standard.Finally,156 patients with small aneurysms and 41 patients with infundibula were included in the study.We separately measured the degree of OA and compared the differences between small aneurysms and infundibula.Results:The patient-based evaluation by OA2 on MRA at 3.0T yielded an accuracy of 95.0%,a sensitivity of 93.6%,specificity of 100%,PPV of 100%,and NPV of 81.3%in the diagnosis of SCAs,which was superior to other three methods of OA measurement.The OA–assisted approach detected 300 SCAs in267 patients and no SCAs in 171,overlooking one aneurysm.Patient-based evaluation yielded high accuracy,sensitivity,specificity,and positive and negative predictive values for the OA–assisted approach.The average OA on MRA was 102.96°±13.36°?range:60°–151°?in 172 SCAs of 156 patients.The average OA on MRA was 69.05°±14.26°?range:35–107°?in 55 infundibula of52 patients.The average OA in SCAs?n=172?was bigger than that in the average OA in infundibula?n=55;102.96°v.s.69.05°,P<0.001?.Conclusions:The OA2 achieved the highest accuracy,sensitivity and specificity among the four OA,and can act as an assisted diagnostic approach for the diagnosis of SCAs in clinic.The OA–assisted approach for SCA diagnosis using MRA effectively minimized the false-positive rate for the subjective approach,with high accuracy,sensitivity,and specificity.These findings suggest that MRA based on this approach can be a reliable alternative for DSA in SCA screening and diagnosis.Furthermore,OA approach at MRA could serve as discriminant for accurate diagnosis and differentiation small SCAs with infundibula.