THE ROLE OF MAGNETIC-RESONANCE ANGIOGRAPHY IN THE DIAGNOSIS OF SUBCLAVIAN STEAL

Purpose: To compare magnetic resonance angiography (MRA) with digital angiography for diagnosis of subclavian steal syndrome. Methods: A com parison study between MRA and digital contrast arteriography was carri ed out in 10 patients with suspected subclavian steal syndrome. Two of these patients were studied by MRA before and after percutaneous tran sluminal angioplasty (PTA). MRA was obtained on a 1.5 tesla supercondu ctive magnet with linear head coil using a fast low angle shot (FLASH 2D) sequence in the axial plane as well as a fast imaging with steady state precession (FISP 3D) with velocity compensation gradient echo se quence in the coronal plane. The coronal images were used as source da ta for the construction of projection images with the use of a maximum -intensity pixel algorithm. The images were rotated from -45 degrees t o 45 degrees in 15 degrees steps. Results: All 10 patients had evidenc e of proximal subclavian artery obstruction and flow reversal in the i psilateral vertebral artery. On MRA, consistent visualization of the a ffected vertebral artery in the FLASH 2D sequences and nonvisualizatio n in the FISP 3D sequences was interpreted as an indirect sign of subc lavian steal. The subclavian artery obstruction could not be assessed due to field size limits of MRA. Conclusion: MRA allows determination of flow reversal in the diagnosis of subclavian steal.