This study is to elucidate the morphologic evolution and remodeling of ICAD under stringent control of cardiovascular risk factors.

The investigator has conducted extensive research on ICAD by transcranial Doppler ultrasound, CT angiography and perfusion studies, magnetic resonance imaging (MRI) and digital subtraction angiography (DSA) respectively. Currently, the investigator applied 3-dimensional rotational angiogram (3DRA), a selective intra-arterial catheter-based imaging technique that had a superior spatial resolution compared with CT, MRI or DSA in depicting minute (<3mm) angio-architecture. Through 3DRA, the investigator could appreciate the ICAD patho-anatomy from a near-infinite number of planes, analyzing the stroke mechanisms and morphological changes with much improved precision. A neuro-radiologist and a stroke neurologist blind to time sequence will measure the geometric parameters and the luminal narrowing by WASID method.

Inclusion Criteria:

1. Patient is 30 to 85 years of age, inclusive.
2. Patients who have an acute infarct in diffusion-weighted MRI compatible with artery-to-artery thrombo-embolism and a relevant intracranial atherosclerotic stenosis ≥60%.
3. Patient who has no contra-indication for the proposed imaging tests.
4. Patient understands the purpose and requirements of the study, and has provided an informed consent.

Exclusion Criteria:

Patient with any of the following conditions would be excluded:

1. Stroke etiology uncertain or unrelated to intracranial atherosclerosis, such as cardioembolism, Moyamoya disease, small vessel disease or primary angiitis of CNS.
2. A tandem stenosis >50% at extra-cranial internal carotid artery.
3. Bleeding propensity: active peptic ulcer disease, major systemic hemorrhage within 30 days, thrombocytopenia (platelets <100 x 109/L), coagulopathy (INR >1.5).
4. A medical condition that would not allow the patient to adhere to the protocol or complete the study.

Patients who have acute cerebral ischemic symptoms attributed to a high-grade (≥60%) stenosis at a middle cerebral artery or intracranial segment of an internal carotid artery (ICA) would be reviewed by neurologists. If their stroke etiology and relevance to ICAD based on clinical syndrome, vascular imaging features and concurrent cardiovascular risks are eligible, they would be invited to join the study.