How does the degree of carotid stenosis affect the accuracy and interobserver variability of magnetic resonance angiography?

摘要

OBJECTIVES—Theaccuracy of magnetic resonance angiography (MRA) was determined inpatients with recently symptomatic tight (80%-99%) carotid stenosis(on Doppler ultrasound), and the effect of stenosis severity on theaccuracy and interobserver variability of MRA was studied.
METHODS—Forty fourconsecutive patients undergoing intra-arterial angiography (IAA) beforecarotid endarterectomy were prospectively studied, in two centres withidentical MR scanners and sequences. All patients had undergone Dopplerultrasound, showing a 70% or worse carotid stenosis on the symptomaticside. MRA and IAA were done during the same admission. The MRA filmswere each independently and blindly read for percentage stenosis(signal gap if present) by four observers. The IA angiograms were readseparately by one observer, blind to symptoms, and Doppler and MRA results.
RESULTS—Signalgaps on MRA were seen in stenoses ranging from 67% to 99% onintra-arterial angiography. Magnetic resonance angiograms consistentlyoverestimated the percentage stenosis according to intra-arterialangiography. Clinically significant misclassification of stenosisoccurred according to MRA in 7% of patients, and was more frequent ascarotid stenosis increased.
CONCLUSION—Significantdiagnostic errors occur with MRA in patients with tight carotidstenosis. Any morbidity occurring as a result of misclassification byMRA is likely to be offset by the avoidance of complications; however,this could only be determined with certainty in a randomised controlled trial.