HIGH-RESOLUTION, MAGNETIZATION-TRANSFER SATURATION, VARIABLE FLIP ANGLE, TIME-OF-FLIGHT MRA IN THE DETECTION OF INTRACRANIAL VASCULAR STENOSES

Objective: Factors that restrict 3D TOF MRA are limited resolution, sa turation of flow, and degree of background suppression. We evaluated M RA for intracranial stenoses by using a 3D TOF technique that minimize s these factors. Materials and Methods: Twenty-nine patients underwent MRA and intraarterial digital subtraction angiography (DSA). The MRA studies were performed on a 1.5 T Siemens SP 4000 system. Integrated t echniques applied to the conventional 3D TOF acquisition included the following: (a) 256 x 256 matrix with a 140 mm FOV and 0.9 mm slice thi ckness, yielding a 0.54 x 0.54 x 0.9 mm(3) voxel; (b) tilted optimized nonsaturating excitation (TONE); and (c) magnetization transfer satur ation (MTS). The intraarterial DSA was performed on a Siemens Angiosta r system with a 1,024 x 1,024 noninterpolated matrix. The MRAs were re viewed by two neuroradiologists. Two hundred seventy-seven vessels wer e evaluated for a total of 806 segments. Vessel segments were evaluate d with a 5 point scale. Results: The estimated accuracy of MRA for det ecting stenosis over all intracranial vessel segments was 0.88 +/- 0.0 3 and 0.89 +/- 0.02 for the two readers, respectively. The estimated a ccuracy ranged from 0.94 +/- 0.02 and 0.93 +/- 0.02 for detecting inte rnal carotid artery stenosis by the two readers, respectively, to 0.65 +/- 0.17 and 0.71 +/- 0.15 for detecting distal vertebral artery sten osis. In vessels determined by catheter angiography to be stenosis-fre e, reader confidence at the proximal versus distal segments was simila r for the internal carotid, basilar, and posterior cerebral arteries. However, for the anterior and middle cerebral arteries, one or both re aders were more confident in diagnosing the proximal segment. Conclusi on: High resolution MTS TONE 3D TOF MRA is an accurate technique for t he screening of medium and large vessel intracranial stenoses.