A pitfall in detection of intracranial unruptured aneurysms on three-dimensional phase-contrast MR angiography.

We report three cases of intracranial unruptured aneurysm evaluated with MR angiography using both three-dimensional time-of-flight and three-dimensional phase-contrast techniques. It has been said that the phase-contrast technique has advantages over the time-of-flight technique in the detection of intracranial aneurysms. However, in our three cases, three-dimensional time-of-flight MR angiography clearly showed the intracranial unruptured aneurysms, but three-dimensional phase-contrast MR angiography failed to show them.