[Diagnostic pitfalls in magnetic resonance angiography].

The authors report on their clinical experience with Magnetic Resonance angiography (MRA) pitfalls. January, 1989, to February, 1995, six hundred MRA examinations were performed in different vascular districts, with a 1.5-T superconductive magnet, the time-of-flight (TOF) technique and 2D and 3D acquisitions. Intracranial arteries, epiaortic vessels and renal arteries were studied with FISP 3D sequences; intracranial veins, thoracic vessels, vena cava and pelvic vessels were studied with FISP 2D sequences. Pitfalls were observed in 56 of 600 MRA exams (9.3%). Of 56 pitfalls, 26 (46.4%) were in epiaortic vessels, 15 (26.7%) in intracranial vessels, 6 (10.7%) in renal arteries, 6 (10.7%) in thoracic vessels, 1 (1.7%) in the inferior vena cava and 2 (3.5%) in iliac vessels. Stenoses were overestimated in 21 patients and underestimated in three; 16 patients were misdiagnosed and 16 were false positives. As for cerebral vascular lesions, 5 aneurysms and 7 transverse sinus thromboses were false positives, while 3 lesions were misdiagnosed as venous angiomas. As for 26 MRA exams of thoracic vessels, stenoses were overestimated in 16 patients and underestimated in 10 patients with subclavian steal syndrome, where the left vertebral artery was misinterpreted as occluded. In 6 MRA exams of thoracic vessels, 1 patient was misdiagnosed as having an aneurysm and 5 patients were misdiagnosed as having lung cancer infiltrating aorta and superior vena cava. As for renal vessels, 2 normal renal arteries were misdiagnosed as false positives and 4 stenoses were overestimated. In the inferior vena cava, a partial agenesis was misinterpreted as thrombosis. In 2 MRA exams of iliac vessels, a stenosis and a thrombosis were misinterpreted as false positives. Our experience suggests that MRA pitfalls are caused by the incorrect use of the various techniques. The pitfalls we observed can be classified as caused by three types of artifacts: saturation, turbulence and paramagnetic substance artifacts.