1. Diagnostic Imaging on Intracranial Atherosclerotic Stenosis Eduardo Freire Mello Department of Interventional Neuroradiology Hospital Espanhol, Salvador - BA, Brasil edufmello@ig.com.br

2. Introduction Intracranial Atherosclerotic Disease accounts for 6 - 10% of all Ischemic Strokes in whites, and may be responsible for 22 - 26% of all IS in Asians 15% risk of recurrent stroke per year Under-recognized cause of stroke Recent advances on clinical and interventional treatment Accurate radiological diagnosis and quantification of the lesions is crucial for treatment planning

3. DSA Gold-standard, but.... Most expensive, invasive and time consuming Stroke risk of 0,7% with permanent disability So, non-invasive methods are required !

4. Transcranial Doppler Least invasive and expensive test Highly operator-dependent Low reproducibility Not technicaly feasible in all patients Not possible to image every vessel

5. MRA X CTA CTA is less susceptible to motion artifacts and less dependent on hemodynamic effects Approach of all proximal portions of the intracranial vasculature with a proper CTA examination and processing techniques Some recent studies have compared the accuracy of MRA and CTA, alone or combined, to DSA (gold-standard)....

6. In 2002 Hirai et al. demonstrated that: MRA alone < CTA + MRA MRA alone has a lower spatial resolution as compared with CTA or DSA, and can cause overestimation of stenosis Accuracy of MRA + CTA ≅ DSA in measuring stenosis and detecting occlusions of the major intracranial arteries SensitivitySpecificityAccuracy MRA92 %91 % MRA + CTA 100 %99 % AJNR Am J Neuroradiol 23:93-101, January 2002

7. In 2005 Bash et al. compared CTA with MRA, using DSA as a gold-standard: CTA has a higher sensitivity, specificity and PPV for the evaluation of intracranial stenoocclusive disease AJNR Am J Neuroradiol 26:1012-1021, May 2005 Stroke. 2008; 39:1184-1188 In 2008 Nguyen-Huynh et al. evaluated the accuracy of CTA for Intracranial Atherosclerotic Disease, comparing to DSA: CTA detected large artery occlusion with 100% sensitivity and specificity For detection of > 50% stenosis CTA had 97,1% sensitivity and 99,5% specificity, and a NPV of 99,8%

8. In 2007 Villablanca et al. compared MDCT Angiography to DSA for detection and quantification of small intracranial arteries, and concluded: MDCT Angiography depicted 90% or more of all examined small intracranial arteries detected with DSA The smallest arterial size reliably detected with CTA was 0,7mm versus 0,4mm for DSA AJR 2007; 188: 593-602

9. CTA`s disadvantages Radiation exposure Time and skill involved in image processing Use of contrast material Possible venous contamination in a region of interest No significant flow information

10. CTA seems to be more accurate than MRA to evaluate intracranial atherosclerotic stenosis Conclusion CTA can be relatively comparable to DSA and presents fewer risks, less costs, is more frequently available and is highly accurate CTA may be considered as the primary study in the setting of suspected intracranial atherosclerotic stenosis