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
Investigation of choice in aoic dissection is 
Select and explain. 
A. USG, B. CT Scan, C. MRI, D. Digital substraction Angiography
C: MRI
Answer: C: MRI 
Explanation: C i.e. MRI Aoic dissection - Most patients are in 50-70 years age group present with very sudden onset pain, often accompanied by tearing sensation. It is usually felt in the precordium & substernal region but may be in back between scapula. These patients are usually misdiagnosed as having cardiac ischemia, which increases risk of complications. - Dialation & dissection in Morphan SyndromeQ are probably caused by a failure to resist shearing stress in media. In Ehlers-DanlosQ collagen molecule abnormalities predispose to dialation & saccular aneurysms but not to dissection these patients have normal resistance to shearing stress. - Stanford classifies it into two types as Type A (involving ascending aoa) - which is more common & carry high probability of complications & moality; and Type B (not involving ascending aoa). * Aoography is the gold standardQ