Usefulness of cranial MR angiography in the screening of intracranial aneurysms and steno-occlusive vascular lesions. Results of secondary interpretation

The purpose of this study was to assess the accuracy of three-dimensional, time-of-flight magnetic resonance (MR) angiography in the detection of intracranial aneurysms and steno-occlusive vascular lesions. A total of 203 patients underwent MR angiography using 1.5 T unit (n=103, group A) and using 1.0 T unit (n=100, group B), as well as conventional angiography or intraarterial digital subtraction angiography. MR angiograms, obtained with a maximum-intensity projection (MIP) algorithm, alone and together with source images were reviewed by six observers in a blinded manner. A total of 68 and 45 aneurysms in groups A and B, respectively, were available for the final review. Receiver operating characteristic analysis revealed sensitivities of 63-82% and 64-87% on MIP and MIP + source images, respectively, in group A; the corresponding figures were 58-89% and 65-91% in group B. For steno-occlusive lesions, there was no difference in the interpretation between MIP alone and MIP + source images. Furthermore, 31 other patients who underwent MR angiography using 1.5 T and 0.5 T units were examined to assess the detectability of both units. The detectability of 1.5 T unit was found to increase by an average of 20%, as compared with 0.5 T unit. MR angiography using 1.5 T unit can depict intracranial aneurysms 5 mm or larger with an accuracy of 75% or more. (N.K.)