In the paper by Wardlaw et al (this issue, pp155–160) the authors consider the question as to whether or not the severity of carotid bifurcation stenosis has some bearing on reader accuracy when interpreting magnetic resonance angiography.1 The answer is yes, assessment becoming less accurate with increase in severity of the stenosis. If we accept that there is an increased risk of complication from conventional angiography in patients with more severe stenoses then the importance of accurate non-invasive …