Can Asperger's Syndrome be detected on an MRI scan?

Yes, it can be. A new scanning method that takes approximately 15 minutes has been developed to help diagnose an autistic spectrum disorder accurately. This is a procedure that confirms or clarifies ASD in a very reliable manner. Scientists have managed to identify parts of the brain associated with autism, when comparing with an ordinary functioning brain. This is with 90% accuracy, according to the institute of psychiatry at Kings College, London.

Not currently, no. Asperger's is a psychological diagnosis, based on behavioral traits. Those aren't detectible via an MRI.

At some point a Functional MRI may be able to determine a diagnosis based on reactions in the brain to specific stimuli, but this is not currently possible.