Diagnosis and quantitation of intracranial stenosis.

Noninvasive tests, transcranial Doppler, magnetic resonance angiography and computed tomography angiography, and invasive catheter angiography are available to diagnose the presence and quantify the severity of intracranial atherosclerotic stenosis. Each test has its advantages and disadvantages, including the gold standard of catheter angiography. Careful use and measurements with any test are crucial to optimal research and treatment of patients suspected of harboring intracranial atherosclerotic stenosis. Rigorous trials assessing the performance of these tests are few in number. The design and results of the SONIA trial are reviewed. The clinical utility of the SONIA approach and data set, in both clinical and research settings, is reviewed.