Unruptured cerebral aneurysms. Evaluation by time-of-flight MR angiography

This communication compares the usefulness and limitations of MR angiography (MRA) and conventional angiography for the detection of unruptured intracranial aneurysms. All 52 patients suspected of having unruptured aneurysms by MRA underwent conventional angiography. A total of 63 unruptured intracranial aneurysms were identified by conventional angiography in 48 of the 52 patients, giving a false positive of 7.7% (4/52). The smallest aneurysms detected by MRA and confirmed by conventional angiography had a diameter of 2 mm. Of the 63 aneurysms, 59 (93.7%) were visualized by MRA, indicating an overall false negative rate of 6.3% (4/63). The false negative rate for medium-sized to giant aneurysm (5 mm or greater) was 0% (0/48), and that for small aneurysms, 26.7% (4/15). In addition, the source image before maximum-intensity projection algorithm and the flow void on thin slice MRI were also useful for rendering an accurate diagnosis. (author)