This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Best test to determine etiology of SAH 
Select and explain. 
A. Enhanced CT, B. Unenhanced CT, C. Intra aerial digital Substraction Angiography, D. MRI
C: Intra aerial digital Substraction Angiography
Answer: C: Intra aerial digital Substraction Angiography 
Explanation: C i.e. Intra aerial digital Substraction Once dx is done by CT Scan; digital substraction angiography (DSA) is done to determine etiology. DSA is most sensitive & best inv. for determining etiologyQ. Now DSA is being replaced by noninvasive methods as MRA (MRI - angiography) & CTA (CT - Angiography).