Validation of transcranial Doppler with CT angiography in cerebral ischaemia: a preliminary pilot study in Singapore

ABSTRACT

<p><b>INTRODUCTION</b>Transcranial Doppler (TCD) is an established tool for the non-invasive assessment of cerebral blood flow. Since TCD results vary with the skills and experience of the sonographer, it requires validation against contrast angiography. We evaluated the diagnostic accuracy of TCD against computed tomography angiography (CTA) and the feasibility of the latter as an additional screening tool in our acute ischaemic stroke patients.</p><p><b>MATERIALS AND METHODS</b>Our stroke unit manages about 700 patients annually. Acute stroke patients undergo TCD for vascular assessment of major arteries of the circle of Willis. Randomly selected acute stroke patients with significant stenosis on TCD underwent high-resolution cranial CTA with multidetector helical scanner. CTA was performed within 24 hours of TCD and images were interpreted by a neuroradiologist blinded to TCD findings. An independent neurosonologist reevaluated TCD if CTA findings were contradictory. Additional information by either modality was also noted.</p><p><b>RESULTS</b>Fifteen patients (12 men, mean age 61 +/- 15years) with cerebral ischaemia and moderate (>50%) stenosis in > or =1 large intracranial arterial segment on routine TCD were evaluated by CTA. Compared with 21 segments of significant stenosis on CTA, TCD showed 16 true-positive, 3 false-positive and 5 false-negative results (sensitivity 76.2%, positive predictive value 84.2%). In 3 cases, TCD showed findings complementary to CTA (real-time embolisation, collateral flow patterns, evidence of distal M2 branch occlusion).</p><p><b>CONCLUSION</b>TCD in our neurovascular laboratory shows a satisfactory agreement with cranial CTA in evaluating patients with cerebral ischaemia. TCD can provide additional real-time dynamic findings complementary to information provided by CTA.</p>